This PDF file contains the front matter associated with SPIE Proceedings Volume 8769, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

This keynote starts from an overview of micro-optics from fundamental functions, fabrication methods and applications in precision engineering and nanotechnology. State-of-the-art measuring systems for surface form metrology of microoptics with micro-structured surfaces, including diffractive micro-optics such as diffraction gratings and refractive micro-optics such as micro lenses and micro-lens arrays, are then be presented. The measuring systems introduced in the presentation are classified into scanning probe microscope-based systems, mechanical stylus profiling systems and optical evaluation systems. Related research activities carried out in the authors' group are also highlighted.

Precise measurements of distance, eccentricity and 3D-shape of fast moving objects such as turning parts of lathes, gear shafts, magnetic bearings, camshafts, crankshafts and rotors of vacuum pumps are on the one hand important tasks. On the other hand they are big challenges, since contactless precise measurement techniques are required. Optical techniques are well suitable for distance measurements of non-moving surfaces. However, measurements of laterally fast moving surfaces are still challenging. For such tasks the laser Doppler distance sensor technique was invented by the TU Dresden some years ago. This technique has been realized by two mutually tilted interference fringe systems, where the distance is coded in the phase difference between the generated interference signals. However, due to the speckle effect different random envelopes and phase jumps of the interference signals occur. They disturb the phase difference estimation between the interference signals. In this paper, we will report on a scientific breakthrough on the measurement uncertainty budget which has been achieved recently. Via matching of the illumination and receiving optics the measurement uncertainty of the displacement and distance can be reduced by about one magnitude. For displacement measurements of a recurring rough surface a standard deviation of 110 nm were attained at lateral velocities of 5 m ∕ s. Due to the additionally measured lateral velocity and the rotational speed, the two-dimensional shape of rotating objects is calculated. The three-dimensional shape can be conducted by employment of a line camera. Since the measurement uncertainty of the displacement, vibration, distance, eccentricity, and shape is nearly independent of the lateral surface velocity, this technique is predestined for fast-rotating objects. Especially it can be advantageously used for the quality control of workpieces inside of a lathe towards the reduction of process tolerances, installation times and costs.

Increasing capabilities in precision manufacturing and micro technology are accompanied by increasing demands of high precision industrial metrology systems. Especially for measuring functional surfaces, areal optical principles are widely used. If, in addition, nanometer height resolution is needed interferometers seem to be the most promising instruments. First, this contribution focuses on the transfer characteristics of white-light interferometers with microscopic field of view. In general, microscopic instruments suffer from their limited lateral resolution capabilities. Hence, the transfer function of these instruments is typically assumed to show a linear low-pass characteristic. We studied the transfer characteristics of white-light interferometers by theoretical simulations and experimental investigations. Our results show that in most practical cases these instruments behave nonlinear, i.e. the output surface profile cannot be obtained from the input profile by a simple linear filter operation. Although they are well-established, there are some further limitations of white-light interferometers if they are used to measure micro or even sub-microstructures. If edges, steeper slopes or abrupt slope changes are present on a measuring object characteristic errors such as batwings occur. Furthermore, a high effort concerning the correction of chromatic aberration is necessary in order to avoid dispersion effects. Otherwise, there will be systematic discrepancies between profiles obtained from evaluation of the coherence peak and those resulting from the phase of the interference signals. These may lead to 2π phase jumps if the fringe order is obtained from the position of the coherence peak. Finally, measurement artifacts may also result if the measured micro-structure shows discontinuities of the surface slope. This contribution analyses the different phenomena and discusses approaches to overcome existing limitations.

Microoptical components play an increasing role in different technology fields such as medical engineering, materials and information processing, imaging and metrology. But their realization needs the combination of modern design concepts with sophisticated processing technologies, new materials and design tools. Furthermore, the introduction of ambitious processing technologies must be accompanied by effective metrology and inspection tools. Therefore, this paper reports about the technologies for making microoptics at ITO. Because sophisticated measurement tools are an indispensable part of the fabrication process, the paper describes our multi-scale inspection approach for the testing of microstructures on wafer-scale level. Finally, some representative applications of microoptical components for advanced measurement and imaging are explained.

Currently, micro-components are required to fabricate with great precision owing to the miniaturization of complex product. In order to assess the dimension, size, and other geometric quantities of such complex micro-components, technological progress is needed in micro- and nano-coordinate metrology. Therefore, the coordinate metrology have been attempted thus far. To establish nano-coordinate metrology with a microprobe technique, we have been developing the optically trapped probe, whose principle is based on the single-beam gradient-force optical trap of a particle in air. However, the rapidly increasing complexity including micro-fine figures makes it difficult to evaluate geometric quantities using a microprobe that can barely access a concave surface. An improved microprobe is required to have a better long working distance, wide measurement range, and high resolution. In this paper, a novel probing technique for coordinate metrology is discussed. The proposed method is based on optical interference, which is seen as a standing wave pattern, also called a standing wave scale. The feasibility is examined by the profile measurement of a smooth surface with high accuracy and the dimensional measurement of a trench structure.

This paper presents a concise description of 3 optical measurement systems that play a critical role in optical lithography of semiconductor devices. A level sensor and alignment sensor are described that are used to measure, respectively, wafer height variations and the wafer location prior to resist exposure. The third sensor is an angle-resolved scatterometer that is used to measure the shape (CD) and placement (Overlay) of the resist patterns. It will be shown how these sensors deal with the common challenge of realizing sub-nm precision on a large variety of product stacks in the presence of process variations.

We propose a real-time 3D capturing-visualization conversion method of light field microscopy. We implement light field microscopy system using conventional optical microscopy and micro lens array, and visualize 3D information from light field microscopy with integral imaging system. We analyze capturing method of light field and how to convert 3D information from light field microscopy to elemental image with corrected depth information for integral imaging in real-time. Experimental setup and result images are presented to verify our proposed method.

We developed a calibration method using a pattern matching method for the SEM equipped with laser interferometer units at an X-Y sample stage. By comparing two images captured before and after the stage movement, an each of moving pixel number to X and Y direction were analyzed using the image processing technique. Then the pixel length was calibrated using stage position data and the pixel data. The developed calibration methods were applied to nano-particle measurements. The sample particle sizes were nominal diameter of 100 nm and 300 nm. Measurement uncertainty evaluation was done and quantitatively reliable results were obtained.

Toroidal surfaces have wide applications in optics and manufacturing industry. Due to the strong aspherical surface profile of a toroidal surface, there are few optical measurement techniques proposed or reported for its measurement. This paper proposed digital Shack Hartmann wavefront sensor (SHWS) with extendable dynamic range. Instead of the traditional spherical lenslet array, which cannot sample the wavefront in two directions simultaneously, an elliptical lenslet array realized by a spatial light modulator (SLM), which provides different optical powers in two directions, is used in the system. With the incorporation of the extended version of the traditional SHWS, the reference-free wavefront sensor (RFWS), curvature matrix is measured, which can be further reconstructed into the surface profile. Both numerical simulation and experimental study has been conducted and the feasibility of measuring toroidal surfaces in the RFWS system with an elliptical lenslet array is proven.

Recently, semiconductor manufacturers have been striving for high speed, large scale multi-layer wafer surface measurement. In this paper, we propose a novel technique in multi-layer wave-front sensing. The measurement uses a gated camera in pico second shutter that can be synchronized to a pico second laser pulse, up to μm accuracy. Subsequently, we propose a compensation technique using time-of-flight wave-front sensing to reconstruct the multilayer surfaces using our proposed gated imaging technique.

Optical imaging techniques have played a major role in understanding the flow dynamics of varieties of fluid flows, particularly in the study of hypersonic flows. Schlieren and shadowgraph techniques have been the flow diagnostic tools for the investigation of compressible flows since more than a century. However these techniques provide only the qualitative information about the flow field. Other optical techniques such as holographic interferometry and laser induced fluorescence (LIF) have been used extensively for extracting quantitative information about the high speed flows. In this paper we present the application of digital holographic interferometry (DHI) technique integrated with short duration hypersonic shock tunnel facility having 1 ms test time, for quantitative flow visualization. Dynamics of the flow fields in hypersonic/supersonic speeds around different test models is visualized with DHI using a high-speed digital camera (0.2 million fps). These visualization results are compared with schlieren visualization and CFD simulation results. Fringe analysis is carried out to estimate the density of the flow field.

Based on digital holographic interferometry (DHI), a method for dynamically measuring the solution concentration variation is introduced. Firstly, a series of digital holograms containing the information of the solution concentration variation is recorded by CCD. Then, according to the relationship between the phase change of the reconstructed object wave and the solution concentration, the two-dimensional (2D) solution concentration distributions in different time are figured out. Taking the measurement of the solution concentration in crystallization process as a sample, the experimental results turn out that it is feasible to in situ, full-field and dynamically monitor the solution concentration variation with the proposed method. We also discuss how to assure the measurement accuracy in following aspects: (1) implementation of the phase correction to eliminate the influence of the environment for the measurement process; (2) determination of the phase calibration base in the space-domain phase unwrapping process according to the time-domain phase unwrapping result of the arbitrary point in solution; (3) the experimental approaches and analysis for improving the measurement accuracy.

X-ray computed tomography (CT) is increasingly used for dimensional metrology, allowing the inspection of both interior and exterior features impossible to observe using traditional optical and tactile measurement techniques. X-ray CT offers many benefits over traditional instruments as a visual inspection tool, however, extracting dimensional information from the reconstructed data-sets must be approached with caution due to error sources that can propagate through the image reconstruction processes. One error source originates from values of the source-to-object and source-to-detector distances; these are critical inputs as they define the voxel size, a global scalar directly influencing all dimensions extracted from the data. To reduce voxel size errors a reference workpiece can be scanned using the same measurement settings as the actual workpiece. By reconstructing the reference workpiece a reference dimension can be evaluated and this then used to adjust the voxel size of the actual workpiece. This reference dimension must be threshold independent, namely it is determined without the influence of edge detection thresholds. This paper offers a reference workpiece designed for measurement in an X-ray CT system, a coordinate measuring machine (CMM), and an optical profiler. Repeated measurements are made of the reference workpiece using all three instruments and

The skin illuminated of two lights at different wavelength can be applied to detect the oxygen saturation of human blood. Due to the absorption coefficient of oxy- (HbO₂) and deoxy- (Hb) hemoglobin are different at the wavelength 660 nm and 890 nm, the transmitted and reflected light within the skin can be used to compute the oxygen saturation image of skin. However, the intensities of skin images illuminated by a 20 mW NIR-LED are too low to determine the position of blood vessel when acquired by the color CCD camera. In order to improve the disadvantages, a mono camera was used and the irradiated distance and angle between LED light and test hand were adjusted to acquire the higher resolution and contrast blood vessel images for the oxygen saturation calculation. In the experiment, we developed the suitable angle to irradiate NIR light is at 75 degrees because the reflected and scattered effect could be generated significantly from both vertical and horizontal direction. In addition, the best contrast vessel images can be obtained when the shutter time is set at 44.030 ms and the irradiated distance was at the range 140-160 mm due to the intensity ratio between tissue and vessel region is the highest and the intensities of image would not be saturated or become too low when these two parameters were adjusted slightly. In future, the proposed parameters and results can be applied to the oxygen saturation measurement in the clinical diagnosis.

In dual wavelength digital holography, a synthetic wavelength is obtained by using two lasers with different wavelengths to expand the measurement range of samples’ step heights from nanometers to micrometers. However, its measurement accuracy reduces along with the expansion of measuring range and significant noise is introduced at the same time. For cases where the sample’s height is smaller than the wavelength of illumination light, the measurement accuracy is very important. In this paper, a new approach of dual wavelength digital holography is presented. The synthetic wavelength is smaller than the wavelength of the two different lasers. Higher measurement accuracy can thus be achieved. The analysis and experimental results show the validity of this method.

We propose a fast and precise optical 3D measurement method. The principle is similar to that of white-light interferometry. The broad-band light source of white-light interferometry is replaced by two lasers with different wavelengths. The object to be measured is placed into one arm of a Michelson interferometer and moved along the optical axis. The intensity measured at the output of the interferometer is equal to the field autocorrelation. In the case of two wavelengths, the autocorrelation is a periodical function with peaks as a result of their beating. The period can be adjusted by the choice of the wavelength difference. By choosing a short period, a fast and precise measurement is performed in the range of a single beat. However, such a measurement is ambiguous if the object has structures deeper than the beat period. The ambiguity is removed by a fast auxiliary measurement with a long beat period covering the whole depth range of the object. The auxiliary measurement need not be precise and can be completed quickly with a large sampling step.

A method based on a free-pose planar target is proposed to calibrate the position and orientation of a one-dimensional rotatable laser monocular vision sensor as well as its camera and laser plane parameters. For sensor parameters calibration, a new invariant in projective geometry, the invariable set of vector products’ orientations, is proposed to sort the control points in each image thus ensure the correct calculation of the control points’ correspondence between target coordinate system and image coordinate system regardless of the pose of the planar target. For sensor pose calibration, a kinematic model is established and a chain transform method is proposed, which enables the transform of images taken in various rotating camera coordinate systems into one same camera coordinate system. With an analysis on eigenvalues and eigenvectors of the transformation matrices, the position and the attitude angle of the sensor is represented in function of time. Verified by experiments, this calibration method has high-freedom operation, simple calibration procedure and ideal calibration accuracy.

The blue light hazard (BLH) to human eye’s retina is now a new issue emerging in applications of artificial light sources. Especially for solid state lighting sources based on the blue chip-LED(GaN), the photons with their energy more than 2.4 eV show photochemical effects on the retina significantly, raising damage both in photoreceptors and retinal pigment epithelium. The photobiological safety of artificial light sources emitting optical radiation has gained more and more attention worldwide and addressed by international standards IEC 62471-2006(CIE S009/E: 2002). Meanwhile, it is involved in IEC safety specifications of LED lighting products and covered by European Directive 2006/25/EC on the minimum health and safety requirements regarding the exposure of the workers to artificial optical radiation. In practical applications of the safety standards, the measuring methods of optical radiation from LED products to eyes are important in establishment of executable methods in the industry. In 2011, a new project to develop the international standard of IEC TR62471-4,that is “Measuring methods of optical radiation related to photobiological safety”, was approved and are now under way. This paper presents the concerned methods for the assessment of optical radiation hazards in the standards. Furthermore, a retina radiance meter simulating eye’s optical geometry is also described, which is a potential tool for blue light hazard assessment of retinal exposure to optical radiation. The spectroradiometric method integrated with charge-coupled device(CCD) imaging system is introduced to provide more reliable results.

Photovoltaic (PV) cells are photo-electrical devices that convert light energy directly into electricity through the photovoltaic effect. PV cell assemblies are used to make solar modules employed in a variety of ways ranging from space applications to domestic energy consumption. Characterisation and performance testing of PV cells are critical to the development of PV technologies and growth of the solar industry. As new solar products are being developed, its energy conversion efficiency and other critical parameters must be accurately measured and tested against globally recognised metrological standards. The differential spectral responsivity (DSR) measurement is one of the primary methods for calibrating reference PV cells. This is done by calculating its spectral responsivities through measuring the AC short-circuit current produced by a PV cell under a modulated monochromatic radiation and different levels of steady-state broadband bias light radiation. It is observed that different types of bias light source will produce different signal-to-noise levels and significantly influence measurement accuracy. This paper aims to investigate the noise sources caused by different types of bias light sources (e.g. xenon arc and tungsten-halogen lamps) and the relevant measurement uncertainties so as to propose a guideline for selection of bias light source which can improve the signal-to-noise level and measurement uncertainty. The DSRs of the PV cells are measured using a commercial DSR measurement system under different levels of bias radiation from 0 to 1 kWm^-2. The data analysis and uncertainty evaluation are presented in this paper using experimental data and mathematical tools.

Integrating sphere is an important tool used in photometry and other optics-related fields to induce uniform scattering of a light source. An important property of an integrating sphere is its uniformity, which should be high so that the sphere provides smooth response. Necessary sphere components include a baffle and a photo-detector. However, the existence of the baffle is found to induce non-uniformity to the sphere response. Here we report an experimental study of the effects of integrating sphere components, especially the baffle, on its uniformity. In a typical condition, the response on the sphere wall opposite to the baffle was found to be lowered compared with that of the surrounding area, while that on the wall around the photo-detector behind the baffle was higher. Consequently, three baffle properties – reflectance of the baffle back surface, baffle size, and baffle position – were varied to see their effects on the sphere response, especially that at the sphere wall behind the baffle. It was found that the amplitude of the response of such area would be lowered regarding the following conditions: decrease in the reflectance of the baffle back surface, decrease in the baffle size, and increase in the distance between baffle and the detector. Adjusting these conditions yielded the lowered signals at such area and hence increasing sphere uniformity. However, the experiment showed that they also induced some adverse effects such as non-uniformity at other parts of the sphere. Thus these conditions should be optimised carefully in order to obtain the best uniformity.

A fiber optics based 1310nm laser was applied with the primary standard cryogenic radiometer for optical power measurement to extend NMC’s spectral responsivity scale toward infrared wavelength. The absolute optical power was measured and two absolute transfer standard detectors (InGaAs based trap detectors) were calibrated at 1310nm. The measurement setup is described and the measurement uncertainty was analyzed. The advantages of using fiber optics based laser sources are discussed in the paper. With the new calibration capability, the uncertainty of the spectral responsivity in the range from 900nm to 1640nm in NMC will be improved.

Using a goniophotometer to implant a total luminous flux measurement, an error comes from the sampling interval, especially in the situation for LED measurement. In this work, we use computer calculations to estimate the effect of sampling interval on the measuring the total luminous flux for four typical kinds of LEDs, whose spatial distributions of luminous intensity is similar to those LEDs shown in CIE 127 paper. Four basic kinds of mathematical functions are selected to simulate the distribution curves. Axial symmetric type LED and non-axial symmetric type LED are both take amount of. We consider polar angle sampling interval of 0.5°, 1°, 2°, and 5° respectively in one rotation for axial symmetric type, and consider azimuth angle sampling interval of 18°, 15°, 12°, 10° and 5° respectively for non-axial symmetric type. We noted that the error is strongly related to spatial distribution. However, for common LED light sources the calculation results show that a usage of polar angle sampling interval of 2° and azimuth angle sampling interval of 15° is recommended. The systematic error of sampling interval for a goniophotometer can be controlled at the level of 0.3%. For high precise level, the usage of polar angle sampling interval of 1° and azimuth angle sampling interval of 10° should be used.

The roughness of teeth' enamel is an important parameter in orthodontics. One example is the application in the process of decreasing tooth-size by reducing the interproximal enamel surfaces (stripping) of teeth. In order to achieve smooth surfaces clinicians have been testing various methods and progressively improved this therapeutic technique. The evaluation the surface roughness following teeth interproximal reduction is fundamental in the process. In general tooth' surface is not flat presenting a variety of complex geometries. In this communication we will report on the metrological procedure employed on the rugometric and microtopographic inspection by optical active triangulation of raw and processed (interproximal stripping) tooth surfaces.

Digital image correlation matches the corresponding locations in the reference and deformed images by optimizing the correlation of the related intensities. Iterative algorithm is regarded as the most effective approach to solving the optimization, but it requires accurate initial guess of the deformation parameters to converge correctly and rapidly. This paper presents a fully automated method which provides accurate initialization for all points of interest in a deformed images and deals with large rotation and heterogeneous deformation. Image features are extracted and pre-matched in the reference and the deformed images. The deformation parameter of a sample point is initialized by the mapping function fitted to the matched features in the vicinity. Once the subsequent iterative optimization achieves a qualified correlation measure, the optimized parameter is used to initiate a parameter transfer. To account for potential deformation difference between successive points, propagation functions are used during the transfer, which are analytically derived to accurately relate the parameters of two points separated by a given distance. The parameter transfer is conducted by the quality of correlation optimization and continued till all the points have been analyzed. Results on both simulated deformations and real-world experiments demonstrate that image features can be reliably matched and automatically generate qualified seed points even in the presence of complex transformation. Parameter transfer using propagation function enables rapid and correct convergence of the nonlinear iterative optimization, allows more flexible choice on the interval between adjacent sample points, and meanwhile handles the heterogeneity of the deformation field.

The systematic strain measurement error in Digital Image Correlation (DIC) induced by the environment temperature variation around the digital camera was extensively studied. The temperature variation of different camera components along with the changes of the environment temperature is experimentally studied and the motions of different components are then analyzed. The strain error in DIC is then analyzed according to a physical model to express the imaging geometry changes. Finally, the DIC measurement error caused by environment temperature variation was experimentally verified.

Digital image correlation (DIC) method is an effective way for full-field strain measurement. Optical flow estimation methods combined with a global searching strategy for displacement field measurement are introduced in this paper. Compared with the conventional DIC method, this strategy can lessen possible mismatching between the reference image and warped image. By minimization the energy function of displacement field, displacement continuity and displacement gradients continuity among calculation points are achieved. For detecting large displacements, a coarse-tofine strategy is also employed. More importantly, the architecture parallelization of optical flow estimation and searching strategy can decrease the running time of this method for time-critical conditions. This proposed method is universally applicable to the images with shadows, rotation, and large deformation. Several pairs of simulated digital speckle images were used to evaluate the performance of this novel DIC method, and the experimental results clearly demonstrate its robustness and effectiveness.

This paper concentrates on the effect of out-of-plane translation on the 2D-DIC and its elimination. The strain errors caused by out-of-plane translation are presented in the form of equations. In this paper, a novel experimental technique is suggested to eliminate the effect of out-of-plane translation in 2D-DIC. A planar laser beam is projected on the surface of the specimen to form a light strip on its surface. The position of the light strip will be shifted if the specimen is translated along the optical axis of the camera. The distance of translation can be calculated by comparing the location of the laser strip before and after translation. Verification experiments were performed to validate the effectiveness of the proposed method. Then the method is combined with the theoretical model to predict and eliminate the pseudo strains caused by out-of-plane translation. Results confirm that this method can predict the strain errors caused by out-of-plane translation to a precision of within 100με.

Since a couple of years, a renaissance of 3dimensional cinema can be observed. Even though the stereoscopy was quite popular within the last 150 years, the 3d cinema has disappeared and re-established itself several times. The first boom in the late 19th century stagnated and vanished after a few years of success, the same happened again in 50’s and 80’s of the 20th century. With the commercial success of the 3d blockbuster "Avatar“ in 2009, at the latest, it is obvious that the 3d cinema is having a comeback. How long will it last this time? There are already some signs of a declining interest in 3d movies, as the discrepancy between expectations and the results delivered becomes more evident. From the former hypes it is known: After an initial phase of curiosity (high expectations and excessive fault tolerance), a phase of frustration and saturation (critical analysis and subsequent disappointment) will follow. This phenomenon is known as “Hype Cycle” The everyday experienced evolution of technology has conditioned the consumers. The expectation “any technical improvement will preserve all previous properties” cannot be fulfilled with present 3d technologies. This is an inherent problem of stereoscopy and autostereoscopy: The presentation of an additional dimension caused concessions in relevant characteristics (i.e. resolution, brightness, frequency, viewing area) or leads to undesirable physical side effects (i.e. subjective discomfort, eye strain, spatial disorientation, feeling of nausea). It will be verified that the 3d apparatus (3d glasses or 3d display) is also the source for these restrictions and a reason for decreasing fascination. The limitations of present autostereoscopic technologies will be explained.

Modern optical metrology applications are largely supported by computational methods, such as phase shifting [1], Fourier Transform [2], digital image correlation [3], camera calibration [4], etc, in which image processing is a critical and indispensable component. While it is not too difficult to obtain a wide variety of image-processing programs from the internet; few are catered for the relatively special area of optical metrology. This paper introduces an image-processing software package: UU (data processing) and Fig (data rendering) that incorporates many useful functions to process optical metrological data. The cross-platform programs UU and Fig are developed based on wxWidgets. At the time of writing, it has been tested on Windows, Linux and Mac OS. The userinterface is designed to offer precise control of the underline processing procedures in a scientific manner. The data input/output mechanism is designed to accommodate diverse file formats and to facilitate the interaction with other independent programs. In terms of robustness, although the software was initially developed for personal use, it is comparably stable and accurate to most of the commercial software of similar nature. In addition to functions for optical metrology, the software package has a rich collection of useful tools in the following areas: real-time image streaming from USB and GigE cameras, computational geometry, computer vision, fitting of data, 3D image processing, vector image processing, precision device control (rotary stage, PZT stage, etc), point cloud to surface reconstruction, volume rendering, batch processing, etc. The software package is currently used in a number of universities for teaching and research.

Off-axis holography records a three-dimensional object into a two dimensional hologram through Leith-Upatneiks geometry. The recovery of 3D object from off-axial hologram, termed as an inverse problem, has been previously implemented by back-propagating (BP) reconstruction. Here we demonstrate the possibility of reconstruction of 3D object from off-axis hologram by combining back-propagating with two-step iterative shrinkage/thresholding algorithms (Twist) and compare it with back-propagating reconstruction of off-axis holography. The results of simulations and experiments show that Twist-BP reconstruction has better performance in eliminating out of focus noise.

Laser Doppler vibrometry(LDV) is a precise and non-contact optical interferometry used to measure vibrations of structures and machine components. LDV can only provide a point-wise measurement, or a scanning measurement via moving the laser beam rapidly onto the vibrating object which is assumed to be invariant in the scanning course. Consequently, LDV is usually impractical to do measurement on transient events. In this paper, a new self-synchronized multipoint LDV is proposed. The multiple laser beams are separated from one laser source, and different frequency shifts are introduced into these beams by a combination of acousto-optic modulators. The laser beams are projected on different points, and the reflected beams interfere with a common reference beam. The interference light intensity signal is recorded by a single photodetector. This multipoint LDV has the flexibility to measure the vibration of different points on various surfaces. In this study, two applications in experimental mechanics area are presented. Firstly, the proposed system is used to measure the resonant frequencies of structure in a shock test. Secondly, The proposed multi-point LDV is also used to measure the mode shape of a beam with an artificial crack. Compared with the original vibration mode shape, the crack location can be identified easily.

We propose a novel multiple image encryption based on fractional Fourier transform (FRT) and known-plaintext attack with modified Gerchberg-Saxton (G-S) phase retrieval algorithm. Multiple images to be encrypted are encoded into corresponding phase-only masks (POMs) using modified G-S algorithm. These POMs are multiplexed into a single POM, which may be referred to as a general key. The individual keys can be generated with the help of all the POMs. Now a random intensity image is encrypted using double phase encoding in which POM and random phase masks (RPM) are used as keys. For decryption, with the concept of known-plaintext attack using intensity image and RPM as keys, the POM is obtained. With this POM, the original images can be retrieved by using individual keys, and correct orders of FRT. We present simulation results with four different gray-scale images. Numerical simulation results support the proposed idea of the multiple image encryption.

A variable-focus cylindrical liquid lens array based on two transparent liquids of different refractive index is demonstrated. An elastic membrane divides a transparent reservoir into two chambers. The two chambers are filled with liquid 1 and liquid 2, respectively, which are of different refractive index. The micro-clapboards help liquid 1, liquid 2 and the elastic membrane form a cylindrical lens array. Driving these two liquids to flow can change the shape of the elastic membrane as well as the focal length. In this design, the gravity effect of liquid can be overcome. A demo lens array of positive optical power is developed and tested. Moreover, a potential application of the proposed lens array for autostereoscopic 3D displays is emphasized.

We present a mathematical modelling and analysis of reflection grating etched Si AFM cantilever deflections under different loading conditions. A simple analysis of the effect of grating structures on cantilever deflection is carried out with emphasis on optimizing the beam and gratings such that maximum amount of diffracted light remains within the detector area.

The digital image correlation (DIC) method has been well recognized as a simple, accurate and efficient method for mechanical behavior evaluation. However, very few researches have concentrated on the relationship between the characteristics of the camera lens and the measurement error of the DIC method. The modulation transfer function (MTF) has commonly used for evaluation of the resolution capability of camera lens. In practice, when the DIC method is used, it is possible that the captured images become too blur to analyze when the object is out of the focus of the camera lens or the object deviates from the line-of-view of the camera. In this paper, the traditional MTF calibration specimen was replaced by a pre-arranged speckle pattern on the specimen. For DIC images grabbed from several selected locations both approaching and departing from the focus of the camera lens, corresponding MTF curves were obtained from the pre-arranged speckle pattern. The displacement measurement errors of the DIC method were then estimated by those obtained MTF curves.

In a wavefront sensing system, the raw data for surface reconstruction, either the slope matrix or curvature matrix, is obtained through centroiding on the focal spot images. Centroiding is to calculate the first moment within a certain area of interest, which encloses the focal spot. As the distribution of focal spots is correlated to the surface sampling condition, while a uniform rectangular grid is good enough to register all the focal spots of a uniformly sampled near flat surface, the focal spots of aspherical or freeform surfaces have varying shapes and sizes depending on the surface geometry. In this case, the normal registration method is not applicable. This paper proposed a dynamic focal spots registration algorithm to automatically analyze the image, identify and register every focal spot for centroiding at one go. Through experiment on a freeform surface with polynomial coefficients up to 10^th order, the feasibility and effectiveness of the proposed algorithm is proved.

With the development of manufacturing industry, the in-situ 3D measurement for the machining workpieces in CNC machine tools is regarded as the new trend of efficient measurement. We introduce a 3D measurement system based on the stereovision and phase-shifting method combined with CNC machine tools, which can measure 3D profile of the machining workpieces between the key machining processes. The measurement system utilizes the method of high dynamic range fringe acquisition to solve the problem of saturation induced by specular lights reflected from shiny surfaces such as aluminum alloy workpiece or titanium alloy workpiece. We measured two workpieces of aluminum alloy on the CNC machine tools to demonstrate the effectiveness of the developed measurement system.

In this paper, a multi-camera DIC system with semi-circular configuration which can capture images from three different view angles at the same time is introduced. The multi-camera DIC system associated calibration method is proposed, the internal- and external- parameters of all system’s cameras by utilizing a planar plate with circular marks on it. A cracked cylindrical were reconstructed with images obtained by the proposed three-camera systems, with the help of digital image correlation method is also demonstrated and discussed.

The exact contact between two rough surfaces is usually estimated using statistical mathematics and surface analysis before and after contact has occurred. To date the majority of real contact and loaded surfaces has been theoretical or by numerical analyses. A method of analysing real contact area under various loads, by utilizing a con-contact laser surface profiler, allows direct measurement of contact area and deformation in terms of contact force and plane displacement between two surfaces. A laser performs a scan through a transparent flat side supported in a fixed position above the base. A test contact, mounted atop a spring and force sensor, and a screw support which moves into contact with the transparent surface. This paper presents the analysis of real contact area of various surfaces under various loads. The surfaces analysed are a pair of Au coated hemispherical contacts, one is a used Au to Au coated multi-walled carbon nanotubes surface, from a MEMS relay application, the other a new contact surface of the same configuration.

The availability of high resolution CCD and CMOS sensors together with the increasing computer capacity have enabled the development of different interferometrical techniques (speckle interferometry, digital holography, digital sherography) which are well suited for real time measurements. Two or more interferograms are recorded on a digital sensor at different times and the deformation of the object occurring between the exposures is calculated from the phase change. Since the process to investigate can be very fast we cannot use the well-known temporal phase shift method for the determination of the phase but we use a spatial carrier method which allows to determine that phase from one single hologram. We will show that this method can be used as well for shearography. Applications of digital holographic techniques for the investigation of vibrations, defect detection in mechanical structure and time resolved measurement of deformation of microelectromechanical systems (MEMS) are presented together with some investigation of mechanical structures by using digital shearography with spatial carrier.

The measurement of the rotating object is of great significance in engineering applications. In this study, a high-speed dual camera system based on 3D digital image correlation has been developed in order to monitor the rotation status of the wind turbine blades. The system allows sequential images acquired at a rate of 500 frames per second (fps). An improved Newton-Raphson algorithm has been proposed which enables detection movement including large rotation and translation in subpixel precision. The simulation experiments showed that this algorithm is robust to identify the movement if the rotation angle is less than 16 degrees between the adjacent images. The subpixel precision is equivalent to the normal NR algorithm, i.e.0.01 pixels in displacement. As a laboratory research, the high speed camera system was used to measure the movement of the wind turbine model which was driven by an electric fan. In the experiment, the image acquisition rate was set at 387 fps and the cameras were calibrated according to Zhang’s method. The blade was coated with randomly distributed speckles and 7 locations in the blade along the radial direction were selected. The displacement components of these 7 locations were measured with the proposed method. Conclusion is drawn that the proposed DIC algorithm is suitable for large rotation detection, and the high-speed dual camera system is a promising, economic method in health diagnose of wind turbine blades.

Optical coherent detection is a precise and non-contact method for measurement of tiny deformation or movement of an object. In the last century, it can only be used on the static or quasi-static measurement of deformation between two statuses. Recently it has been applied on dynamic measurement with the help of high-speed camera. The advantage of this technique is that it can offer a full-field measurement. However, due to the limited capturing rate of high-speed camera, its capability in temporal domain cannot meet the requirements of many applications. In this study, several issues in high-speed-camera-based optical interferometry are discussed. For example, introduction of carrier in temporal and spatial domain, signal processing in temporal-frequency domain, and the introduction of dual-wavelength interferometry in dynamic measurement. The discussion leads to a clue to select suitable technique to fulfill whole-field dynamic measurement at different ranges.

We describe a spectroscopic ellipsometer which uses a variable waveplate to generate four phase-stepped intensities I (λ) of a white light source which are recorded by a small spectrometer. At each wavelength, the variable waveplate produces a constant, but unknown phase step α. We use Carré’s algorithm to determine the unknown phase step α at each wavelength and thence the ellipsometric angles ψ and Δ. We demonstrate our new instrument experimentally by measuring the retardation of an achromatic waveleplate and determining the thickness of silicon dioxide films on a silicon substrate.

A laser beam is scanned on an object surface with a fast scanning system which consists of a rotating mirror, a flat mirror, and a concave spherical mirror. Propagation direction of the laser beam reflected by a sample surface is detected with a lens and a position sensitive detector. A one-dimensional surface profile of the sample surface is measured by integrating a slop distribution obtained from the propagation direction of the reflected beam. The measurement is insensitivity to mechanical vibrations because of a high-speed scanning of a few milliseconds. The required positioning accuracy of the sample surface is lower than a few millimeters. The measurement repeatability is less than 10 nm.

Compact and stable phase stepping interferometer for shape and full field displacement measurement in static and in “real time” operation mode is presented. Double symmetrical illumination of the object in two orthogonal planes with diode lasers, emitting in NIR (790 nm and 830 nm), through a four-exposure reflective holographic optical element (Denisiyk’s volume reflection holograms of a reference plane) is applied. Phase stepping is introduced simply by precise increments of the diode lasers current. The proposed system is very stable against external noise, produced by vibrations, temperature changes, air flows, as well as against the influence of object’s “rigid body” motion, as the compact and low weight interferometer can be stably fixed directly onto the measured construction.

Photovoltaic (PV) cells, or solar cells, take advantage of the photoelectric effect to convert solar energy to electricity. With rapidly increasing of demands of new and green energy, solar energy industry becomes more important in the global economic development. PV cells are the building blocks of all PV systems because they are the devices that convert sunlight to electricity. Characterization and performance testing are critical to the development of existing and emerging photovoltaic technologies and the growth of the solar industry. As new solar products are being developed and manufactured, the energy conversion efficiency and other critical parameters must be accurately measured and tested under globally recognized standard testing conditions which include solar cell temperature, spectral distribution and total irradiance level of solar radiation on the cell to be tested. The aim of this paper is to investigate one of critical parameters – solar cell temperature effect on measurement of spectral responsivity of the cell. When a reference solar cell is illuminated by solar radiation, the cell temperature will vary with different irradiance levels. Consequently it will affect the accurate measurement of spectral responsivity of the cell. In order to better understand the temperature effect on the measurement, temperature coefficients of reference solar cell in spectral range from 300 nm to 1000 nm are measured in temperature range from 25 oC to 35 oC. The measurement uncertainties of temperature coefficient are evaluated and described in this paper according to JCGM 100: 2008 (ISO/IEC Guide 98-3) - Guide to the expression of uncertainty in measurement.

As the demand for micro-patterned parts getting bigger, the need for molds with micro/nano scaled patterns to duplicate these parts effectively and economically is increasing ever so rapidly. Over the years, numerous attempts have been made to fabricate these molds using various approaches such as lithography, FIB, laser ablation, and precision diamond turning. Amongst these approaches, diamond turning is by far the most commonly used method to generate the micropatterned rollers for roll-to-roll fabricating of precision optical parts such as BEF and 3D films. However, micro-burrs are frequently produced during the micro-cutting process which not only makes the mold un-usable but also increases the cost of machining. Efforts have been made to study the burr formation process during the micro-cutting by FEM simulation, micro-scratching and diamond turning. Influences of the machining parameters such as rake angle, cutting edge radius, included angle and cutting speed on the burr formation were systematically investigated. Array of micropyramids with 90° apex angle, 40*40μm² basal area and minimised burr were successfully produced on a OFCu roller of 270mm in diameter. The results showed that (i) tool rake angle, included angle and cutting edge radius have profound effect on burr formation and achievable surface finish, (ii) simulation can supply very useful information for setting the machining parameters to suppress the burr formation during micro-cutting process.

The generation of microstructures by ultrashort pulse laser irradiation is - depending on process parameters and the applied material - often accompanied with the creation of substructures like ripples or micro canals on the ablation ground. This side effect can be used to create local topographic modifications on a microscopic scale which can change functional properties of the surface. The combination of micro structuring and functionalisation within one production step can only be successful if the interaction mechanisms are well known. In this study the options to modify the wetting behavior on stainless steel, Al₂O₃ ceramic and PMMA plastic were analyzed. Therefore the contact angles of water drops on picoseconds-laser-produced samples were measured by a self-made measuring system. Test measurements offered post-process effects on surfaces of steel and ceramic. On those substrates the final contact angle adjusts after several hours up to days. In total with this technique contact angles between 5° and 160° could be realized, depending on the material. This allows generation of hydrophilic up to super-hydrophobic effects on precise defined areas. The combination technique offers novel options particularly for micro fluidic. Some produced samples for “Lab-on-a-Chip- Systems” should demonstrate that.

In this study, it is of interest to find a way to inspect transparent circuits with narrow line widths (<30 μm). A PDLC/ITO film with a thinner PET layers (1 and 5 μm) will be adopted as the sensing device. Simulations were conducted to evaluate the performance of the proposed system and study effects of system parameters on the limitation of the proposed system.

Serious geological hazard such as the roof fall、rib spalling、closure deformation of the cavity can exert bad influence to mine, even threaten human life. The traditional monitoring ways have some disadvantages, which are difficulties in obtaining data of the cavity, monitoring the unmanned cavity and calculating volume of the cavity accurately. To solve these problems, this paper describes how to develop a high precision 3D laser scanning system, which enables scanning the cavity rapidly, obtaining the same resolution point cloud, calculating volume of the cavity, marking the deformation area correctly and providing visualized environment. At the same time, this device has realized remote control functionality to avoid people to work on the underground. The measurement accuracy of the 3D laser scanning system is ±2cm. The 3D laser scanning system can be combined with the mine microseism monitoring system to help with the estimation the cavity’s stability and improve the effect of cavity monitoring.

This paper is not an original paper, but a review paper passed on our previous papers. We have been developing a few apparatuses for 2D and/or 3D profile measurement because these systems, especially 3D profiling systems, have become indispensable tools in manufacturing industry. However, in surface profile measurement, conventional systems have several short comings including being very large in size and heavy in weight. Therefore we propose to realize a compact portable apparatus on the basis of pattern projection method using a single MEMS mirror scanning. On the other hand, in the case of inner profile measurement for pipes or tubes, we propose to use optical section method by means of disk beam produced by a conical mirror. In these systems development of elements and devices such as a MEMS mirror and/or cone mirror play important role to apply our fundamental principles to practical apparatuses. We introduce the state of the art of these systems including commercialized products for practical purpose.

Three-dimensional (3-D) shape measuring techniques, using a combination of grating projection and a most frequently used mathematical tool--Fourier fringe analysis, have been deeply researched and increasing in numbers. Such kind techniques are based on the idea of projecting and superposing a carrier fringe pattern onto the surface of the tested object, and then reconstructing its corresponding 3-D shape from the deformed fringe pattern modulated by the height of the tested object and captured by a camera from other view direction. This paper mainly reviews the basic principles and its typical applications of the combined technology based on grating projection and Fourier fringe analysis that we have developed over past ten years in the research field of dynamic 3-D shape measurement. Meanwhile, the advantages and challenges of this technique and the current development of real-time measurement in this research filed are also described as a discussion and conclusion in this paper.

Holography, in which three-dimensional (3D) information and texture of object is encoded with interference fringe is a promising approach for 3D display. However, it is challenge to make photographic hologram of living object. In addition, it is impossible to record scene combining real-existing objects with virtual ones using photographic holography. In this paper, we propose a method for capturing and displaying 3D real-existing scene. Firstly, the 3D shape and color texture of scene is captured with fringe projection method. Secondly, the information of scene is encoded with computer generated fringe, which is called Computer-generated Hologram (CGH). Finally, the CGH is materialize as hardcopy or transferred to spatial light modulator (SLM) for display. The real-color Rainbow-hologram is chosen for display static scene. Three Fresnel holograms corresponding to red, green and blue component of scene are adopted for display dynamic scene. The apparatuses for 3D capture and display are introduced and the experimental results are demonstrated.

High-speed shape measurement is required to analysis the behavior of a breaking object, a vibrating object or a rotating object. A shape measurement by a phase shifting method can measure the shape with high spatial resolution because the coordinates can be obtained pixel by pixel. The key-device is a grating projector. The projector can shift the projected grating in high-speed. So, authors proposed a light source stepping method using a linear LED device. A grating projector is composed with the linear LED and a Ronchi ruling. Grating pattern can be projected when the linear LED is turned on. The phase of the projected grating on the object can be shifted with changing the position of lighted linear LED easily and quickly. Authors call this method a light source stepping method. In this paper, a linear LED grating projector is developed. The characteristic of the linear LED grating projector such as the wavelength, directional characteristics, response are evaluated. The results show that this projector is useful for high-speed shape measurement.

The three-dimensional (3D) metrology for specular reflecting surfaces attracted much attention due to their various applications in optics, electronics, or semiconductor industry. Fringe reflection technique is an effective tool to measure the specular surface slopes (gradient information), and then reconstruct the surface shape from gradient. However, most of the fringe reflection systems are built up for middle size (~10,000 mm²) or larger size (~100,000 mm²) objects by using the off-the-shelf desktop displays. In order to measure samples with smaller size (~200 mm₂) with higher measuring resolution, a compact fringe reflection system is proposed. The performance of the compact specular 3D shape measurement system is demonstrated with experiments.

In phase measuring deflectometry (PMD), the fringe pattern deformed according to slope deviation of a specular surface is digitized employing a phase-shift technique. Without height-angle ambiguity, carrier-removal process is adopted to evaluate the variation of surface slope from phase distribution when a quasi-plane is measured. This paper investigates nonlinear carrier components introduced by the generalized imaging process in PMD and the nonlinear carrier removal methods. To remove the nonlinear carrier components in PMD, the reference subtraction technique, series-expansion technique and Zernike polynomials which are normally used in fringe projection profilometry are analyzed on accuracy, processing time and experimental simplicity. What’s more, a new nonlinear carrier removal technique is proposed according to the analytical expression of carrier phase. The theoretical analysis and the experiment results show that the new technique is accurate, simple and time-saving.

Pattern recognition by using joint transform correlator with JPEG-compressed reference images is studied. Human face and fingerprint images are used as test scenes with different spatial frequency contents. Recognition performance is quantitatively measured by taking into account effect of imbalance illumination and noise presence. The feasibility of implementing the proposed JTC is verified by using computer simulations and experiments.

The phase unwrapping is the final and trickiest step in any phase retrieval technique. Phase unwrapping by artificial intelligence methods (optimization algorithms) such as hybrid genetic algorithm, reverse simulated annealing, particle swarm optimization, minimum cost matching showed better results than conventional phase unwrapping methods. In this paper, Ensemble of hybrid genetic algorithm with parallel populations is proposed to solve the branch-cut phase unwrapping problem. In a single populated hybrid genetic algorithm, the selection, cross-over and mutation operators are applied to obtain new population in every generation. The parameters and choice of operators will affect the performance of the hybrid genetic algorithm. The ensemble of hybrid genetic algorithm will facilitate to have different parameters set and different choice of operators simultaneously. Each population will use different set of parameters and the offspring of each population will compete against the offspring of all other populations, which use different set of parameters. The effectiveness of proposed algorithm is demonstrated by phase unwrapping examples and advantages of the proposed method are discussed.

Repeated plastic instability accompanying serrated yielding in stress–strain curves and localization of deformation is observed during plastic deformation of many metallic alloys when tensile specimens are deformed under certain experimental conditions of temperature, strain rate, and pre-deformation. This phenomenon is referred to as the Portevin- Le Chatelier (PLC) effect. TMW alloy, a newly developed Ni–Co base superalloy for aircraft engine application, also exhibit PLC effect during tensile test at temperatures ranging from 300 ℃ to 600 ℃, which are also the temperature range for engine working. In this paper, a 3D digital image correlation (3D DIC) measurement system was established to observe the localization of deformation (PLC band) in a tensile test performed on TMW alloy specimen at temperature of 400 ℃. The 3D DIC system, with displacement measurement accuracy up to 0.01 pixels and strain measurement accuracy up to 100 με, has a high performance in displacement field calculation with more than 10000 points every second on a 3.1G Hz CPU computer. The test result shows that, the PLC bands are inclined at an angle of about 60° to the tensile axis. Unlike tensile test performed on aluminums alloy, the widths of PLC bands of TMW alloy specimen, ranging from 4 mm to 4.5 mm, are much greater than the specimen thickness (0.25 mm).

Windowed Fourier ridges algorithm can provide a quality map to assist the quality-guided phase unwrapping. Its performance for discontinuous phase maps is investigated in this paper, where the influence of window size in the algorithm is examined. Three discontinuous phase boundaries, straight, curved, and fused, are tested for both noiseless and noisy situations. Encouraging results are observed. Small window size can be used for higher boundary detection accuracy and can be enlarged if noise is heavy and/or the discontinuities are not obvious in a small area.

We present a method for quantitative phase recovery using the axially defocused intensity information based on the phase optical transfer function in defocused situation. The image formation process is linearized by subtraction of two intensity images with equal and opposite defocus distances and quantitative phase information is separated and extracted by solving an inverse problem with Wiener filtering. Experiments confirm the accuracy and stability of the proposed method outperforms the transport-of-intensity reconstruction method.

Because of larger measurement ability of wave-front deviation and no need of reference plat, the lateral shearing interferometry based on four step phase shifting has been widely used for wave-front measurement. After installation shearing interferograms are captured by CCD camera, and the actual phase data of wave-front can be calculated by four step phase shift algorithm and phase unwrapping. In this processing, the pixel resolution and gray scale of CCD camera is the vital factor for the measurement precision. In this paper, Based on the structure of lateral shearing surface interferometer with phase shifting, pixel resolution more or less for measurement precision is discussed. Also, the gray scale is 8 bit, 12 bit or 16 bit for measurement precision is illustrated by simulation.

A focused Ga⁺ ion beam is used to mill a multilevel spiral phase plate at an acceleration voltage of 30 kV. Circular spiral phase plate with eight levels is fabricated directly on an indium-tin-oxide coated glass plate. Scanning electron microscopy images demonstrate the realization of multilevel phase plate on glass plate using focused ion beam milling.

Two-photon polymerization is a powerful technique in the area of functional micro/nano device fabrication. The greatest limiting factor in widespread use of this technique is the low efficiency because the structure is fabricated by point-by-point scanning. In recent years, computer generated hologram is used for parallel fabrication via multi foci. In this paper, we proposed a new rapid fabrication method which use desirable multi-focus pattern as scanning cell instead of single focus point or foci array to polymerize. We establish a femtosecond laser experimental setup involved in a liquid crystal spatial light modulator. The computer generated hologram pattern on spatial light modulator is used to produce desirable foci array. The position and intensity of each focus in the pattern can be controlled well by optimal design. We use multi foci in a line as scanning cell to fabricate some revolving structure and the Fresnel lens can be expected. This work provides a new method to greatly improve the efficiency of two-photon polymerization production in fabricating revolving structures.

As the demand for precision optical components with sub-millimeter feature size steadily increasing, numerous efforts have been made in developing new techniques and in improving the existing approaches to efficiently and economically produce those components. Glass molding process (GMP) is one of these methods to enable mass production of precision glass optical components in recent years. One of the key issues in GMP is precision mold insert fabrication. Since the mould are normally made of hard and brittle materials such as tungsten carbide (WC) and silicon carbide (SiC), precision diamond grinding is by far the principal choice used to machine the GMP mould. As the feature size of optical component gets smaller, the size of mould and grinding wheel used to fabricate the mould gets smaller too. This makes the grinding process a very time consuming and expensive task. This research aimed to improve the small mold fabrication processes by developing an effective way of producing small diamond wheels and in-process monitoring wheel profile. Diamond wheels of around 0.2mm to 0.5mm in diameter after truing and WC aspheric mold insert of form accuracy around 0.47μm were successfully produced in this research.

This paper reports on the evolution of femtosecond laser induced periodic surface structures (LIPSSs) on titanium surface irradiated with different wavelengths. By SEM observations, it is noted that different nanostructures with respective surface features depend highly on the laser wavelength and the laser fluence. The period of LIPSSs formed at the laser fluence just above the ablation threshold is shorter than the laser wavelength, as well as dependence on the incident wavelength. Experiments using wavelength of 600 and 1500 nm, studies are performed in more detail. The period and the depth of the grooves of LIPSSs are increased with the increase of laser fluence at wavelength of 600nm. The created structures on the surface at the laser fluence of 0.42 J/cm² would significantly influence the field intensity distribution on the surface. The redistribution of the electric field intensity plays a crucial role in the creation of the HSFLs formed on the ridges of the LIPSSs, and the period decreases to half. Another kind of HSFLs whose orientation is perpendicular to the sidewalls of LIPSSs is created at wavelength of 1500nm. These HSFLs lie at the bottom of the valleys between both the LIPSSs and new formed grooves. As compared with the surface nanostructures formed at wavelength of 600 nm, the formation of identical HSFLs is induced with smaller laser fluence at wavelength of 1500 nm.

We demonstrate the fabrication of a white light blinded IR photo-detector sing a Si based metal insulator semiconductor (MIS) structure with multi-layers of SiO₂/TiO₂ dielectric and its characteristics of photo -responsivity. Spectral responsivity peak at 850 nm with high discrimination in visible light had been achieved in a MIS photo -detector with multiple layers of SiO₂/TiO₂ dielectrics. Reflection spectral measurements and I -V characteristics of the SiO₂/TiO₂ multi-layers with various layer number and thickness were used to explore the photo -detection in this MIS device structure. We found that high spectral discrimination of visible light of this multi-dielectric layers MIS device is due to the optical filtering property by these multi -layers and the mid-band gap impurity states existed at the interface between the Si substrate and these dielectric layers.

The performances of two liquid level sensors based on Fiber Bragg grating are studied. The Fiber Bragg gratings (FBG) are sensitive to strain and temperature. We investigate on enhancement of strain sensitivity of the FBG for liquid level measurement. Two different sensor heads arrangement are fabricated to exploit the strain sensitivity of FBG and use it for the liquid level measurement. The measurement sensitivity of a FBG based fiber optic liquid level sensor can be improved by controlling the parameter such as diameter of the FBG.

Most of the reported optical techniques of encryption in literature belong to the category of symmetric cryptosystems, in which the keys used for encryption are identical to the decryption keys. In an environment of network security, a symmetric cryptosystem would suffer from problems in key distribution, management, and delivery. In this paper, we present the results of an asymmetric cryptosystem that uses fractional Fourier transform domain amplitude- and phase- truncation approach. The input image/data used are gray-scale and color patterns. The conventional random phase masks are replaced with structured phase masks to further enhance the key size and hence security of cryptosystem. The scheme also uses the concept of interference and polarization selective diffractive optical element. Cryptanalysis has been carried out considering various types of attacks using phase retrieval algorithm. Numerical simulation results have been presented.

A new color image cryptosystem is proposed, which is based on discrete cosine transform and spiral phase encoding in gyrator transform domain. The random phase mask is replaced by a multiple-key spiral phase mask, because it is difficult to replicate and easy to align. In this scheme, a color image is decomposed into red, blue and green color channels. Each channel is encoded independently by using discrete cosine transform and then encrypted into a spiral phase mask. The resulting image is gyrator transformed. The operations are performed twice continuously to get multiplexed encrypted image at output plane. The rotation angles of gyrator transform along with the order, the wavelength, the focal length and the radius of a spiral phase mask of each channel provide multiple choice for the parameter of the proposed security system as encryption keys. The proposed optical setup avoids alignment problems. The performance, feasibility and effectiveness of the proposed algorithm are demonstrated by the numerical simulation results.

A novel method for image encryption under spatially incoherent illumination is proposed. The LED array is used as the spatially incoherent source. Both the encryption process and decryption process are numerically simulated. Experiments are carried out to demonstrate the basic ideal of the proposed method. The incoherent light is modulated by the spatial light modulator on the input plane as the input image to be encrypted. Then a random phase only mask is used as the key to encode the image, finally a Fourier lens is adopted to image the encrypted image on the output plane. The encrypted intensity distribution is recorded by a CCD. In the numerical simulations, the random phase only mask is generated by a rand function. The incoherent image is composed of many source points, and any two points of these sources are spatially incoherent, but each point is self-spatially coherent. Under this property, the point spread function for the encryption system can be considered as the interference of two beams, one is the spherical beam and the other is the random phase beam. Once the point spread function is given, the system’s optical transfer function can be calculated easily. Then the encryption system can be considered as a decryption system, and the output image is the same as the original image. The encrypted image can be calculated with the system’s optical transfer function and the output image. The random phase mask, the distance between the random phase mask and the SLM, and the wavelength of the laser can be seen as the keys of the encryption systems. Only when all these parameters are correct, can one get the right decrypted image. The factors which could affect the practical experiment, such as quantization noise and displacement tolerances are also investigated. Compared with the conventional coherent encryption system, the incoherent encryption system proposed in this paper is free of the flaws of the optical elements, the dust particles on the elements, and other unstable factors of the environment. What’s more, the cost of the incoherent encryption system is lower since only a phase only mask and a imaging lens are used.

A novel blind video watermarking scheme offering a low computational complexity is presented in which the computer generated holograms are used as the watermarks. In the scheme, the original video is divided into nonoverlapping groups of pictures (GOPs). A quantization method is used to insert the mark hologram into the low frequency wavelet coefficients of every GOP. The extraction procedure does not need the original video. Experimental results demonstrate that the presented scheme is transparent and robust to a variety of attacks, including compression, noise addition, filtering, occlusion, cropping and temporal attacks, etc. One of the most important advantages of the suggested method is its simplicity and practicality.

Detection of petroleum leakages in pipelines and storage tanks is a very important as it may lead to significant pollution of the environment, accidental hazards, and also it is a very important fuel resource. Petroleum leakage detection sensor based on fiber optics was fabricated by etching the fiber Bragg grating (FBG) to a region where the total internal reflection is affected. The experiment shows that the reflected Bragg’s wavelength and intensity goes to zero when etched FBG is in air and recovers Bragg’s wavelength and intensity when it is comes in contact with petroleum or any external fluid. This acts as high sensitive, fast response fluid optical switch in liquid level sensing, petroleum leakage detection etc. In this paper we present our results on using this technique in petroleum leakage detection.

This paper includes design and simulation of high sensitivity Fiber Bragg Grating (FBG) sensor for pressure measurement under water. This paper involves simulation of a super structure FBG which is encapsulated with a polymercompletely- filled metal cylinder. An observation has been made to see the effect of polymer coating on the FBG for pressure sensitivity. The novel scheme of this analysis is to design a high sensitivity pressure sensor and simulate it using ANSYS, the FBG is designed using R-soft and MATLAB is used for plotting the change in the Braggs wavelength with application of the polymer.

We demonstrate an application of fiber Bragg grating to measure the index of refraction of an unknown liquid by using a cladding depleted FBG. The measurements of the index of refraction were calibrated by the index oil with known index of refraction. Samples of liquid with difference percentage of sugar content were prepared and measured the index of refraction using this method. It shows that accuracy of index of refraction measurement as high as 0.01 can be achieved.

From the sensitivity of the FBG center wavelength changing with strain changes on the surface, the design of a FBG strain-based asphalt pavement pressure sensor is described by designing a special FBG asphalt box-film packaging structure. The compactness and simplicity of the device are achieved by using the corresponding package obtained from common available asphalt. Numerical analysis and experimental results show that the response of the sensor has good regularity for a wide range of travel (0MPa to 5.3312MPa). In the load range, the FBG center wavelength increases from 1548.264nm to 1548.346nm which shows a good correspondence with loads. Linearity, travel and sensitivity are experimentally determined by different packaging parameters. A design chart that includes the travel (0MPa to 5.3312MPa) and the sensitivity (15.3812pm/MPa) is finally proposed.

Wavelength-swept laser technique is an active demodulation method which integrates laser source and detecting circuit together to achieve compact size. The method also has the advantages such as large demodulation range, high accuracy, and comparatively high speed. In this paper, we present a FBG interrogation method based on wavelength-swept Laser, in which an erbium-doped fiber is used as gain medium and connected by a WDM to form a ring cavity, a fiber FP tunable filter is inserted in the loop for choosing the laser frequency and a gas absorption cell is adopted as a frequency reference. The laser wavelength is swept by driving the FP filter. If the laser wavelength matches with that of FBG sensors, there will be some strong reflection peak signals. Detecting such signals with the transmittance signal after the gas absorption cell synchronously and analyzing them, the center wavelengths of the FBG sensors are calculated out at last. Here, we discuss the data processing method based on the frequency reference, and experimentally study the swept laser characteristics. Finally, we adopt this interrogator to demodulate FBG stress sensors. The results show that, the demodulation range almost covers C+L band, the resolution and accuracy can reach about 1pm or less and 5pm respectively. So it is very suitable for most FBG measurements.

A high sensitive pressure sensor based on Fiber Bragg grating (FBG) integrated with a thin metal diaphragm was designed and demonstrated. To enhance the pressure sensitivity FBG is firmly glued across the diameter of the diaphragm. Under pressure, the diaphragm deforms and produces an induced strain along the length of the fiber causes shift in Bragg wavelength of the FBG. Pressure measurement is made by measuring the Bragg wavelength shift against change in pressure. The sensor was tested up to the maximum pressure of 140 psi and the corresponding pressure sensitivity was found to be 0.0204 nm/psi, which is approximately 970 times higher than that can be achieved with a bare FBG. The experimental results show good agreement with the theoretical results and possess good linearity and repeatability. This sensor can be used for the measurement of medium pressure, liquid level and depth of underwater.

The fibers aligning is very important in fusion splicing process. The core of polarization maintaining photonic crystal fiber(PM-PCF) can not be seen in the splicer due to microhole structure of its cross-section. So it is difficult to align precisely PM-PCF and conventional single-mode fiber(SMF).We demonstrate a novel method for aligning precisely PM-PCF and conventional SMF by online spectrum monitoring. Firstly, the light source of halogen lamp is connected to one end face of conventional SMF.Then align roughly one end face of PM-PCF and the other end face of conventional SMF by observing visible light in the other end face of PM-PCF. If there exists visible light, they are believed to align roughly. The other end face of PM-PCF and one end face of the other conventional SMF are aligned precisely in the other splicer by online spectrum monitoring. Now the light source of halogen lamp is changed into a broadband light source with 52nm wavelength range.The other end face of the other conventional SMF is connected to an optical spectrum analyzer.They are translationally and rotationally adjusted in the splicer by monitoring spectrum. When the transmission spectrum power is maximum, the aligning is precise.

A simple noncontact fiber optic vibration sensor is designed using multimode fiber optic coupler. The sensor works on principle of reflection intensity modulation. A single fiber port of the coupler is used as sensing head. A linear change in light intensity during its displacement from the reflecting surface within 1 mm of linear region shows a high sensitivity of 2.45 mV/μm which is used for the vibration measurement. Experimental results show that the sensor has the capability of measuring vibrations of frequencies up to 1300 Hz with ~1μm resolution of vibration amplitude over a range of 0-1mm. In comparison with dual-fiber and bifurcated-bundle fiber, this sensor eliminates the dark region and front slope which facilitates the easy alignment. The high degrees of sensitivity, economical along with advantages of fiber optic sensors are attractive attributes of the designed sensor that lend support to real time monitoring and embedded applications.

An intensity based fiber optic liquid level sensor for continuous measurement is described. The sensing principle is based on intensity of reflected light which is disturbed by the change in proximity of the fiber probe and the reflector. A Mechanical CAM is used in the sensing arrangement. It converts the rotatory motion into a linear displacement. As the liquid level raises, rotation of the CAM takes place and the CAM follower connected to it moves linearly. A reflector which is attached to the end of the CAM follower reflect the incident light. As the displacement of reflector occur the intensity of reflected light also changes and is a measure of change in liquid level. The prototype designed sensor can sense liquid level upto 17cm. The proposed sensor can find potential applications in transportation and process industries.

In this study, the novel rotation algorithm is proposed for the phase unwrapping algorithm. The main advantage of proposed algorithm is that it can simultaneously resolve the shifting error, holes, two types of noise (i.e. the residual noise and noise at height discontinuities). By contrast, the common phase unwrapping algorithms which operate phase shifting by 2π, can only filter two types of noise. Unfortunately, these common algorithms can not resolve the problems of the shifting error and holes. Therefore, compared to these common algorithms, the proposed rotation algorithm is more effective and useful for resolving the problems of holes and noise.

Phase analysis plays a role in optical science and technology. For instance, phase analysis technique has been widely used for 3-D shape and deformation measurement by fringe projection profilometry. To analyze the phase distribution of a single fringe pattern, various fringe pattern analysis methods such as a Fourier transform, a wavelet transform, and the windowed Fourier transform have been developed. In this study, a fast phase analysis technique, i.e., two-dimensional sampling moiré method, is proposed to determine accurately the phase distribution of a single fringe pattern by using two-dimensional intensity information. In this method, we record diagonally a single fringe pattern image by using a CCD camera, and perform the image processing of down-sampling with a sampling pitch and intensity interpolation in both x- and y-directions to generate a two-dimensional phase-shifted moiré fringe. Then, the phase distribution of the moiré fringe can be determined by using phase-shifting method and a two-dimensional discrete Fourier transform (DFT) algorithm. Finally, the desired phase distribution of the original fringe pattern can be obtained by adding the phase of the sampling point to the phase of the moiré pattern. By the proposed method, the phase error caused by the random noise of the camera can be dramatically decreased because the intensity information is much richer than one-dimensional intensity data, which utilizes a two-dimensional DFT algorithm. The fundamental principle and primary simulation and experimental results are presented. Theses results show that phase analysis can be performed under extremely low signal-to-noise ratio measurement condition.

Partial differential equations (PDEs) and ordinary differential equations (ODE) based image processing methods have been demonstrated to be a powerful tool for optical fringe processing. In this paper, we review our works on PDEs (ODEs)-based image processing methods for optical interferometry fringe processing, including the anisotropic filters, the ODE enhancement methods, the ODE- PDEs filtering and enhancing models and the skeletonization of optical interferometry fringe based on PDEs.

In the past two decades, fringe projection profilometry (FPP) has been widely used in three-dimensional (3D) profile measurement for its fast speed and high accuracy. As a branch of FPP, color-encoded digital fringe projection profilometry (CDFPP) has been applied to surface profile measurement. CDFPP has the advantage of being fast speed, non-contact and full-field. It is one of the most important dynamic 3D profile measurement techniques. However, due to color cross-talk and gamma distortions of electro-optical devices, phase errors arise in using conventional phase-shifting algorithms to retrieve the phase in CDFPP. Therefore, it is important to develop methods for phase error suppression in CDFPP and thus realizing fast and accurate profile measurement. In this paper, a phase error suppression technique is proposed to overcome color cross-talk and gamma distortions. The proposed method is able to carry out fast and accurate surface profile measurement. The real data experimental results show that the proposed method can effectively suppress phase errors and achieve accurate measurements in CDFPP.

Ellipsometers based on heterodyne interferometers are inherently capable of precise measurements, with the ellipsometric angles determined from the amplitude and phase of a pair of quadrature signals. These signals are generally displayed as a Lissajous figure and the primary limitation to accuracy is determined by the goodness-of-fit to the ellipse, especially for ellipses with high ellipticity. In this paper we describe an improvement to the ellipse­ fitting algorithm of Halir & Flusser. A Michelson interferometer was constructed and a polarizer-quarterwave plate combination used to generate ellipses of moderate to extreme ellipticity. We show experimentally that our method yields excellent fits, even for axis ratios approaching 300: 1, yielding a one-sigma error of 0.5 mrad (less than λ/10000) in the presence of measurement noise.

Dynamics of single and two collinearly colliding laser ablated plumes studied using fast imaging and the spectroscopic measurement is reported. The two expanding plumes colliding with each other resulting in the formation of a stagnation layer at the interface region which depend on mean free path and distance between the two plumes. The overlapping region lasts for several microseconds with significant concentration of nanoparticles/ cluster in gaseous phase. The dynamical growth of ZnO nanoparticles is ascertained using Rayleigh scattered second harmonic radiation at 532 nm of Nd:YAG laser. Intensity variation in the Rayleigh scattered signal and blue shift in photoluminescence peak position at different temporal delays with respect to the ablation pulse corroborates the presence and size variation of nano-particles/clusters formed in the vapor phase of ablated ZnO. The thin films of ZnO deposited on glass (polycrystalline) substrate are observed to have preference for single orientation. The presence of low ionic species in the overlap region seems to play a role in getting singly oriented thin films.

Photochromic film of Spirooxazine-incorporated organosillicates material was prepared by sol-gel method and deposited on quartz substrate. The film was examined through the variation of UV irradiation power and exposure time for optical behavior characterizations. Investigations have been carried out by UV-Vis spectrophotometry and spectroscopic reflectometry. It was found that the absorption spectra of film at the region of 230-250nm were decreased indicating the reduction of C=C to C-C bond with increased of power and exposure time of UV irradiation were increased. On the other hand, we observed that the photo transformation absorption peak was also change at the region of 610nm to 620nm when different duration of UV irradiation applied. In addition, this UV curing process also increased the refractive index of film since the structures become compacted due to reduction of pore size volume in the system. Thus it will limit the film ability to performed photo transformation which will contribute to the reduction of film coloration upon UV irradiation. It is concluded that consideration of power and duration of UV irradiation is significant for designing the function of photochromic film in led their successful use in various applications.

A general analytical transient temperature field expression of KDP crystal irradiated by sinusoidal modulated laser is obtained by the integral transform method, based on the heat conduction equation of the orthotropic material. The influence of radius, power and frequency of the laser on the transient temperature field of KDP crystal is simulated by Matlab. The results show that the temperature of material has stepwise distribution with time, which shows periodical stable distribution after some time, and it increases with the decrease of the laser radius and the increase of the laser power. The above results provide a theoretical basis for the photothermal displacement technology used in the measurement of the opto-thermal parameters of the KDP crystal.

We report an easily fabricated, broadband and high-absorbance coating for terahertz absolute radiometry. The spectral property of this coating was characterized in THz region with a home-made terahertz time-domain spectrometer. The measured results showed an extremely low spectral reflectance ranging from 0.1 THz to 2.0 THz. We assembled a terahertz radiometer with this coating as absorber. This coating is highly absorptive both in terahertz region and in visible light; therefore, the power responsivity of this radiometer is easily traceable to Chinese National Laser Power Standard. This coating is useful in traceability of terahertz sources and detectors to the SI units, and it will play an important role in infrared and far infrared absolute radiometry.

The mechanical and thermal stress on lens will cause the glass refractive index different, the refractive index of light parallel and light perpendicular to the direction of stress. The refraction index changes will introduce Optical Path Difference (OPD). This study is applying Finite Element Method (FEM) and optical ray tracing; calculate off axis ray stress OPD. The optical system stress distribution result is calculated from finite element simulation, and the stress coordinate need to rotate to optical path direction. Meanwhile, weighting stress to each optical ray path and sum the ray path OPD. The Z-direction stress OPD can be fitted by Zernike polynomial, the separated to sag difference, and rigid body motion. The fitting results can be used to evaluate the stress effect on optical component.

We report here, a finite difference thermal diffusion (FDTD) model for controlling the cross-section and the guiding nature of the buried channel waveguides fabricated on GeGaS bulk glasses using the direct laser writing technique. Optimization of the laser parameters for guiding at wavelength 1550 nm is done experimentally and compared with the theoretical values estimated by FDTD model. The mode field diameter (MFD) between 5.294 μm and 24.706 μm were attained by suitable selection of writing speed (1mm/s to 4 mm/s) and pulse energy (623 nJ to 806 nJ) of the laser at a fixed repletion rate of 100 kHz. Transition from single-mode to multi-mode waveguide is observed at pulse energy 806nJ as a consequence of heat accumulation. The thermal diffusion model fits well for single-mode waveguides with the exception of multi-mode waveguides.

One of the major problems of designing an illumination optical system is the repeatedly time-consuming ray-tracing process while optimizing the illumination optical system parameters. This study proposes a “one-time ray-tracing method” for the optimization of illumination systems. As a demonstration, this study designs a planar lightguide backlight with uniformly irradiance at the light-exiting surface using the proposed one-time ray-tracing method. In this method, the irradiance distributions of the target region are related to the radiant intensity distribution of the side planar light sources. Using only one-time ray tracing and the optimization of the light source radiant intensity, the proposed method can quickly find a design of the planar lightguide backlight for providing an uniformly irradiance distribution at target illumination region. That is, with only one-time ray tracing and the optimization technique, the CV(RMSR) (coefficient of variation of root mean square error), of the target region irradiance distribution was decreased to 0.06 from 0.12. The proposed method holds great potential to the designing illumination systems, since it can be applied to design not only the planar lightguide but also other optical illumination systems.

Effect of stress and interface defects on photo luminescence property of a silicon nano-crystal (Si-nc) embedded in amorphous silicon dioxide (a-SiO₂) are studied in this paper using a self-consistent quantum-continuum based modeling framework. Si-ncs or quantum dots show photoluminescence at room temperature. Whether its origin is due to Si-nc/a- SiO₂ interface defects or quantum confinement of carriers in Si-nc is still an outstanding question. Earlier reports have shown that stresses greater than 12 GPa change the indirect energy band gap structure of bulk Si to a direct energy band gap structure. Such stresses are observed very often in nanostructures and these stresses influence the carrier confinement energy significantly. Hence, it is important to determine the effect of stress in addition to the structure of interface defects on photoluminescence property of Si-nc. In the present work, first a Si-nc embedded in a-SiO₂ is constructed using molecular dynamics simulation framework considering the actual conditions they are grown so that the interface and residual stress in the structure evolves naturally during formation. We observe that the structure thus created has an interface of about 1 nm thick consisting of 41.95% of defective states mostly Siⁿ⁺ (n = 0 to 3) coordination states. Further, both the Si-nc core and the embedding matrix are observed to be under a compressive strain. This residual strain field is applied in an effective mass k.p Hamiltonian formulation to determine the energy states of the carriers. The photo luminescence property computed based on the carrier confinement energy and interface energy states associated with defects will be analysed in details in the paper.

It is very important to monitor and control pH during cell and tissue culture. On-line pH monitoring provides valuable information on cell metabolic processes and living environment. A novel simple method to real-time measure pH during cell and tissue culture has been experimentally demonstrated using a tapered optical fiber coated with polyaniline. The fiber is tapered to produce the leaking mode in the sensing film. The absorption coefficient and the refractive index of the polyaniline film will vary with different pH values and resultantly change the optical spectral responses. The optical power droped with the increase of the pH at 1042nm. Such a device is sensitive to pH allowing the determination of pH values ranging from 5 to 11 and the resolution of the order of 0.03. Comparing to the conventional pH glass electrode, this optical measurement has smaller size, faster response and can avoid the contamination of the cell and tissue culture fluid.

In this study, multivariate data analysis, especially partial least squares regression (PLSR), is applied to analyze the near infrared absorbance spectra of fruit samples in order to acquire the inner qualities without destroying the samples. The calibration models have been established for the samples with raw data, first order derivative and second order derivative treatments, respectively. In the meantime, the models have been verified by using cross validation method. As anticipated, a model with higher correlation coefficient (r) and lower root mean square error of calibration (RMSEC) is preferred for both calibration and cross validation. The results reveal that the calibration models with second order derivative treatments have higher correlation coefficient, coefficient of determination, as well as lower RMSEC. Furthermore, the calibration models have been optimized by selecting partial wavelengths as new variables based on absorbance spectra and regression coefficient. The reasons why the calibration models are improved might be suitably cutting off partial wavelengths causing noises in the model.

In this paper, 2 sub machine vision based alignment systems were used to establish a high speed alignment system for screen printing. It can be used on the solar cell and flat display panel manufacture. The 2 sub alignment system can auto align target simultaneously. When one target was takes out, another target can implement auto alignment simultaneously. It can save the wait time for target take out procedure. The sub alignment system includes 4 CCD cameras, 4 lens, 4 outer coaxial LED light sources, a vacuum table and a 3 axis motorized stage. The alignment accuracy is about 1 μm.

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is a special quasi-meridian reflecting Schmidt telescope that is installed with 4000 optical fibers, and these fibers should precisely align the celestial target when the astronomical observation is performing. Hence, it is necessary to kwon the precise position of the fiber end for tracking the celestial target. The existence of various error sources can affect the process of camera calibration and measurement, causing the measurement results to be less accurate than expected. In order to acquire the precise position of the fiber end on the focal plane of LAMOST, a novel algorithm for fiber end positioning based on the bundle adjustment and laser tracker is proposed in this paper. We also need reduce some error sources. The bundle adjustment algorithm applied in the paper has been implemented with special emphasis on accuracy and performance efficiency. The preliminary results show that this new bundle adjustment algorithm can achieve better accuracy than conventional calibration method. The precision error of fibers position is less than 17μm on the plane of the mechanical structure movement.

In the traditional fringe reflection method for specular surface measurement, the change of phase is only due to the gradient changes. Through the gradient-based phase unwrapping algorithms eventually restored the surface shape. However, due to the approximate nature of the formula itself, the broadness and accuracy of measurement is limited in a certain range within. The actual change in phase comes from the gradient and the surface shape itself together. Therefore, the absolute phase and the surface shape model and the face shape recovery algorithm based on recursion were presented in this paper. Using the model in this paper largely makes up for the deficiencies of the traditional algorithm. A good effect in surface shape recovery has been achieved through the experiment.

This study proposes a simple method for measuring two-dimensional temperature distributions. Using the significant phase difference between p- and s-polarizations of the reflected light of a surface plasmon resonance (SPR) detector, the variation in the phase difference, which is caused by a variation in the temperature, can be accurately measured by phase-shifting interferometry. Then, by substituting the phase distribution into special derived equation, the temperature distribution can be determined. In order to show the feasibility of this method, different temperature distributions were measured. The measurement resolution is about 0.186°C. Due to the introduced common-path configuration and the high-sensitivity characteristic of surface plasmon resonance, this method should have merits of easy operation, high sensitivity, high accuracy and rapidly measurement.

The absorbing filter [1] is an optical element employed for isolating regions of a spectrum. In general, the thicker the absorbing filter material, the more wavelengths it will absorb. However, most optical filter products ignore light diffusion and are made with a constant thickness. While the non-collimated beams pass through the filter, the optical paths vary with incident angles. Thus, the absorption difference happens and leads to the poor uniformity of transmission spectrum. In our work, a filter lens was developed to achieve the similar function of interference filter and ND filter with better spectrum uniformity. It is mounted onto a designed macro lens and supplies it with a good spectrum aberration correction. The shape of the filter lens is designed to eliminate the optical path differences between the light beams in the medium. The macro lens is made of neutral glass and shaped into symmetrical biconvex for achieving macro imaging. The spectrum characteristic of the filter lens depends on the material of the absorbing filter. In the experiment, the filter lens was prepared. The experimental results show that the spectrum uniformity of the filter lens is better than that of the normal filter.

Due to its advantages of non-contact, full-field and high-resolution measurement, digital image correlation (DIC) method has gained wide acceptance and found numerous applications in the field of experimental mechanics. In this paper, the application of DIC for real-time long-distance bridge deflection detection in outdoor environments is studied. Bridge deflection measurement using DIC in outdoor environments is more challenging than regular DIC measurements performed under laboratory conditions. First, much more image noise due to variations in ambient light will be presented in the images recorded in outdoor environments. Second, how to select the target area becomes a key factor because long-distance imaging results in a large field of view of the test object. Finally, the image acquisition speed of the camera must be high enough (larger than 100 fps) to capture the real-time dynamic motion of a bridge. In this work, the above challenging issues are addressed and several improvements were made to DIC method. The applicability was demonstrated by real experiments. Experimental results indicate that the DIC method has great potentials in motion measurement in various large building structures.

Power spectral density (PSD) is being used to evaluate the surface finish and wavefront errors in mid-spatial frequency of optical components, but whether a PSD curve is credible or not is now a problem to be solved urgently. PSD curves measured by different instruments make an influence on the estimate of optical components. In order to solve this problem, we use system transfer function (STF) to find the relationships between different instruments and PSD measurements. A mathematical model of STF and PSD measurement is established to stimulate and find the floor level of STF to get a credible PSD. The experiment results that the instruments with STF at least 60% can be used in mid-spatial frequency measurements.

Digital holography is a new imaging technique, which is developed on the base of optical holography, Digital processing, and Computer techniques. It is using CCD instead of the conventional silver to record hologram, and then reproducing the 3D contour of the object by the way of computer simulation. Compared with the traditional optical holographic, the whole process is of simple measuring, lower production cost, faster the imaging speed, and with the advantages of non-contact real-time measurement. At present, it can be used in the fields of the morphology detection of tiny objects, micro deformation analysis, and biological cells shape measurement. It is one of the research hot spot at home and abroad. This paper introduced the basic principles and relevant theories about the optical holography and Digital holography, and researched the basic questions which influence the reproduce images in the process of recording and reconstructing of the digital holographic microcopy. In order to get a clear digital hologram, by analyzing the optical system structure, we discussed the recording distance and of the hologram. On the base of the theoretical studies, we established a measurement and analyzed the experimental conditions, then adjusted them to the system. To achieve a precise measurement of tiny object in three-dimension, we measured MEMS micro device for example, and obtained the reproduction three-dimensional contour, realized the three dimensional profile measurement of tiny object. According to the experiment results consider: analysis the reference factors between the zero-order term and a pair of twin-images by the choice of the object light and the reference light and the distance of the recording and reconstructing and the characteristics of reconstruction light on the measurement, the measurement errors were analyzed. The research result shows that the device owns certain reliability.

Inspired by dominant flight of the natural flyers and driven by civilian and military purposes, micro air vehicle (MAV) has been developed so far by passive wing control but still pales in aerodynamic performance. Better understanding of flapping wing flight mechanism is eager to improve MAV’s flight performance. In this paper, a simple and effective 4D metrology technique to measure full-field deformation of flapping membrane wing is presented. Based on fringe projection and 3D Fourier analysis, the fast and complex dynamic deformation, including wing rotation and wing stroke, of a flapping wing during its flight can be accurately reconstructed from the deformed fringe patterns recorded by a highspeed camera. An experiment was carried on a flapping-wing MAV with 5-cm span membrane wing beating at 30 Hz, and the results show that this method is effective and will be useful to the aerodynamicist or micro aircraft designer for visualizing high-speed complex wing deformation and consequently aid the design of flapping wing mechanism to enhanced aerodynamic performance.

Differential optical absorption spectroscopy (DOAS) has become a widely used method to measure trace gases in the atmosphere. The concentrations of trace gases can be retrieved by fitting differential absorption spectra with standard differential absorption cross-section using the linear least-square method. The basic principle of DOAS is introduced. The construction of DOAS on-line monitoring system is designed and the retrieval method of trace gases concentration based on the principle of least-squares is discussed. The properties of DOAS system are tested by experiments. The advantages of DOAS system used in atmosphere quality monitoring are shown.

The Chinese magic mirror is an ancient convex bronze mirror, it reflects parallel light rays to form a unique image within the reflected patch of light by altering the reflected ray paths. Using Phase Measuring Reflectometry (PMR), surface irregularities of a micron range were found to be present on the mirror; these irregularities concentrate and disperse reflected light rays, giving rise to brighter and darker patches on the reflected image, forming a contrast, allowing the unique pattern to be observed. To ascertain location and nature of the surface defects that come in forms of indentations and raised platforms, other measurement techniques were employed. Reverse engineering then facilitated the exploration of reproduction of a very own original Chinese Magic Mirror with the use of optical principles behind the mirror.

We present a single-shot experimental configuration for quantitative phase microscopy recovery based on the transportof- intensity equation (TIE). The system can simultaneously capture two laterally separated images with different amounts of defocus using only one digital camera. The defocus distance can be adjusted by varying the free space propagation transfer function on a phase only spatial light modulator. The intensity derivative along optics axis can thus be estimated optimally. In contrast to the state of the art techniques, this configuration requires no mechanical moving parts. Furthermore its single-shot property allows potential application for measuring fast moving objects or dynamic processes. Validation experiments are presented.

The yellow-ring (YR) is a chromatism phenomenon which is caused by the inhomogeneous phosphor layer of the whitelight LED (WLED) and can be observed from the projected WLED lightspot. In general, the lights emitted from a WLED will focus on the specific range to form a circular lightspot; in the meanwhile, the YR will appear on the periphery of this lightspot. In our previous study, the evaluation of YR phenomenon was graded by the YR index (YRI), which is the product of the yellow light intensity (Y) and total light intensity (I). Therein, the maximum value of YRI is a crucial optical parameter for determining the YR degree and a YR evaluation model is as the criterion for quality control of WLED. In this article, the YR distribution of MR-16 triplet lens module related to the distance (pitch) between two of three WLEDs will be discussed. Experimental results show that the YRI of triple lens WLED module is lower than one of single lens WLED module due to the overlapped effect of WLED lightspots. In addition, the YR degree of triplet lens WLED module will be lower if the pitch is longer, but the unintended dark-corner effect will appear when the pitch is enough longer.

Many of the conducting polymers though having good material property are not solution processable. Hence an alternate method of fabrication of film by pulsed laser deposition, was explored in this work. PDTCPA, a donor- acceptor- donor type of polymer having absorption from 900 nm to 300 nm was deposited by both UV and IR laser to understand the effect of deposition parameters on the film quality. It was observed that the laser ablation of PDTCPA doesn’t alter its chemical structure hence retaining the chemical integrity of the polymer. Microscopic studies of the ablated film shows that the IR laser ablated films were particulate in nature while UV laser ablated films are deposited as smooth continuous layer. The morphology of the film influences its electrical characteristics as current- voltage characteristic of these films shows that films deposited by UV laser are p rectifying while those by IR laser are more of resistor in nature.

Optical freeform surfaces are complex surfaces with non-rotational symmetry that break through the limitations of conventional optical element, and are widely used in advanced optics application for system configuration simplifying and performance enhancing. Due to the geometrical complexity and optical particularity of optical freeform surfaces, there is, as yet, a lack of precision freeform surfaces testing. Computer generated hologram (CGH) null testing method are discussed in this paper to test the optical freeform surfaces such as off-axis aspheric surfaces. CGH design based on ray tracing and NURBS interpolation are included. Simuation in Zemax is given to verify the result of calculation. The alignment and fiducial sections are added to the CGH to lead the alignment of the freeform surface and CGH with sixdimensional adjustment. The CGH was designed and fabricated to test an off-axis aspheric with Fizeau configuration.

A novel surface plasmon polariton-based waveguide (or called plasmonic waveguide) is proposed to achieve millimeter-scale propagation distance while maintaining subwavelength mode area. For easy to practically fabricate, the proposed structure is consisted of a cylinder metallic nanowire bounded by a high-index contrast dielectric material on a low-index dielectric substrate. The cladding region of the proposed structure is air. To satisfy the index matching condition, we vary the thickness of the high-index dielectric above the cylinder nanowire. A symmetric mode field profile exhibiting the lowest resistive loss resulted from the metal is thus obtained to accomplish the low-loss propagation. The proposed plasmonic waveguide could offer plasmonic circuit interconnects and high-density integrated photonic circuits.

A new methodology is developed for the realisation of primary spectral radiance scale for supporting high power LED and solid state lighting (SSL) characterisation. The scale is realised using a multi-wavelength filter radiometer (MWFR) and a variable high temperature black body (VTBB) as reference source. The MWFR contains 24 band pass filters with centre wavelengths from 250 nm to 1600 nm. It is used to determine the spectral radiance of the black body at different wavelengths so as to estimate the black body temperature and calculate the continuous spectral radiance of the black body. With the known continuous spectral radiance, the black body can be employed to calibrate the system response of a double grating monochromator and detectors. The calibrated values will be transferred to a set of standard lamps. These standard lamps will then be used to calibrate commercial spectroradiometers for measuring the spectral radiance of sample lamps such as LED and SSL. The results obtained will allow characterisation of the LED/SSL to be done with proper traceability to the primary standard.

This paper is to describe a color digital holographic projector and this system is comprised of RGB lasers, 3 units of Digital Micro-Mirror Device (DMD) and high speed rotating diffuser. In this research, we focused on colorings Digital holograms and synchronized RGB digital holograms versus rotated diffuser. To achieve this phenomenon, three of the holograms optical path need to be aligned to pass through a same beam splitter and eventually combined as one colored holograms output While, this colored hologram will be reconstructed on volumetric screen (rotated diffuser) at the floating manner in free space. To obtain these result 3 key factors is investigated: 1. To configured 1 master and 2 slaves digital micro mirror illumination time 2. To reconstructed holograms orientation angle diffuser versus rotating speed. 3. To synchronize rotating diffuser speed versus DMD frame-rate Last but not least, the team built a prototype Color Digital Holography Display but more developments are required to follow up such as, enhance system's reliability, robustness, compactness and 3D realistic images floating in the free air space.

A novel three dimensional profilometry technique by optical fiber interference projection was presented. Take the wavelength-modulated laser as the light source to make the purpose of interference fringe phase-shift by changing the wavelength of the precision power. Compare with the traditional means what changing the phase by PZT, the new method is easier in phase calibration and phase-shift controlling for its anti-interference and having no hysteresis. In addition, the experimental equipment can be associated with commercial interferometer so that their software can be taken as the tool for data processing.

In the optoelectronic reconstruction of full-color hologram, transverse and longitudinal chromatisms are introduced due to the hologram is sensitive to wavelength, which makes the colorful image fuzzy. The image quality is also affected by the characteristic of the spatial light modulator used in optoelectronic projection system. Multi-order diffraction images occurred due to the ratio of active area and dead area (fill rate). In the colorful holographic projection system, three lasers with red, green, and blue color are applied as the light sources, color crosstalk due to the switching of the different lasers also impairs the image quality. In order to improving the image quality of full color holographic projection system, this paper analyzes the effect of the fill rate and the color crosstalk on the reconstruction image quality. Transverse and longitudinal chromatisms are removed by resampling the object information and loading a specially designed virtual phase distribution in the computer hologram respectively. We proposed time sequence updating chart of RGB laser to solve the problem of color crosstalk. Experimental results are also provided to verify the improvement of the image quality.

In the phase-shift based lidar system, a distance between the lidar and an object can be determined via the phase difference between the reference signal and measured signal. The maximum unambiguous range for the phase-shift based lidar is inversely proportional to the modulation frequency of the signal. When the modulation frequency is increased for high distance resolution, the unambiguous range is decreased. In this paper, we described a method to extend the unambiguous range of the lidar, which is a considerable disadvantage of the phase-shift measurement method. In addition, we propose a method for implementing dual frequencies modulation technique with two laser diodes.

A numerical method is investigated to design gradient-index (GRIN) fiber probes. The GRIN fiber probe is composed of a single mode fiber (SMF), a no-core fiber (NCF), and a GRIN fiber lens. The optical software GLAD is adopted to simulate the optical performance of the probe. The simulation results show that, given the length of the GRIN fiber lens 0.1mm and the length of the NCF 0.36mm, the working distance is 0.73mm and the focus spot size 33μm, which are well agreement with the experimental data. As a result, the proposed numerical method is validated to be effective to design such GRIN fiber probes.

An electrical tunable lens is applied in digital holographic microscopy for physical spherical phase compensation. When different microscope objectives are applied to one digital holographic microscope, the physical spherical phase compensation needs different reference wavefronts. The focal length of the electric tunable lens can be adjusted by applying different voltages. We have measured the morphology changes of the tunable lens under different voltages. According to the measurement, the tunable lens has the capability to change wavefront via changing of the applied voltages. Thus we apply the tunable lens in the digital holographic microscope with multiple microscope objectives to fulfill the physical spherical phase compensation. The measurement results for the tunable lens together with the phase compensation results are presented.

This study proposes a Fresnel lens with multiple focus modes by combining the technology of polymer stabilized liquid crystals (PSLC) with the novel electrode design, which contains the Fresnel zone electrodes and complementary electrodes. The device was fabricated according the methods including the photolithography for the electrode patterns, the LC cell assembly, and the UV exposure for the PLSC curing. Experimental results show that the diffraction effects of the lens can be switched under different operation modes. It can accordingly provide three focal lengths of 25 cm, 32 cm, and 39.5 cm.

Fluorescence objects can be excited by ultraviolet (UV) light and emit a specific light of longer wavelength in biomedical experiments. However, UV light causes a deviation in the blue violet color of fluorescent images. Therefore, this study presents a color deviation adjustment method to recover the color of fluorescent image to the hue observed under normal white light, while retaining the UV light-excited fluorescent area in the reconstructed image. Based on the Gray World Method, we proposed a non-linear logarithm method (NLLM) to restore the color deviation of fluorescent images by using a yellow filter attached to the front of a digital camera lens in the experiment. Subsequently, the luminance datum of objects can be divided into the red, green, and blue (R/G/B) components which can determine the appropriate intensity of chromatic colors. In general, the datum of fluorescent images transformed into the CIE 1931 color space can be used to evaluate the quality of reconstructed images by the distribution of x-y coordinates. From the experiment, the proposed method NLLM can recover more than 90% color deviation and the reconstructed images can approach to the real color of fluorescent object illuminated by white light.

The core of the power inductor is made by powder metallurgy. By its nature, the powder-formed part has inherent nonuniform porosity pattern and parallel tool marks on the metal surface. In the past, the surface inspection of core is usually performed by using human eyes. However, the larger uncertainty of inspection will be induced while observing the defect image using human eyes. In the automated optical inspection process, the feature of defect is not easily separated from the image background by using the simple binarization method. This study develops an image processing method and employs a uniform diffuse illumination to build up a surface defect inspection system. Experiment result shows the distinguish rate is 95.5%, therefore it is clear that this system can successfully detects a set defect of the core of inductor.

A half-Bessel beam (HBB) is one of nonparaxial and nondiffracting accelerating beams that follows a circular trajectory. Since the ideal HBB is a beam of infinite energy, it is impossible to generate an ideal HBB. Therefore, truncation is necessary to make the beam be square integrable. There exist two ways of such truncation. One is simply cutting off some portion of the beam, and the other is modulating the angular spectrum of the beam. For the latter method, Fourier transformation optics based on a lensed system can be applied. In this study, we suggest and numerically evaluate several methods to achieve finite HBBs using conventional Fourier-optic 2-f system. To this objective, we first derive an angular spectrum representation of the ideal HBB. From this, we show that the obtained spectrum has poles in Fourier domain. After that, several forms of square integrable finite HBBs, where the poles are eliminated, are suggested. And then, the characteristics of the proposed finite HBBs in terms of diffraction and acceleration are presented.

The tomographic refractive index imaging technique by digital holographic microscopy with sample rotation is presented. First, transmission phase images are numerically reconstructed from holograms acquired at regularly-spaced angular positions for the rotating sample. Then, the three-dimensional refractive index spatial distribution is reconstructed by filtered back-projection algorithm. Last, the experiments are carried out and the three-dimensional refractive index distribution of single-mode and single-mode polarization maintaining optical fibers is accurately reconstructed.

The performance of Atomic Force Microscope depends on the control gains. However, the optimal gains have uncertainties which are impacted by cantilever properties, sample properties and measurement environment. In commercial AFM, it is not easy to get good AFM imaging results since the controller is manually tuned by user. In this paper, auto gain tuning algorithm is suggested for the high performance and automation of AFM. Auto gain tuning algorithm is evaluated by step responses, frequency responses and AFM imaging results.

Upper gastrointestinal endoscopies are primarily performed to observe the pathologies of the esophagus, stomach, and duodenum. However, when an endoscope is pushed into the esophagus or stomach by the physician, the organs behave similar to a balloon being gradually inflated. Consequently, their shapes and depth-of-field of images change continually, preventing thorough examination of the inflammation or anabrosis position, which delays the curing period. In this study, a 2.9-mm image-capturing module and a convoluted mechanism was incorporated into the tube like a standard 10- mm upper gastrointestinal endoscope. The scale-invariant feature transform (SIFT) algorithm was adopted to implement disease feature extraction on a koala doll. Following feature extraction, the smoothly varying affine stitching (SVAS) method was employed to resolve stitching distortion problems. Subsequently, the real-time splice software developed in this study was embedded in an upper gastrointestinal endoscope to obtain a panoramic view of stomach inflammation in the captured images. The results showed that the 2.9-mm image-capturing module can provide approximately 50 verified images in one spin cycle, a viewing angle of 120° can be attained, and less than 10% distortion can be achieved in each image. Therefore, these methods can solve the problems encountered when using a standard 10-mm upper gastrointestinal endoscope with a single camera, such as image distortion, and partial inflammation displays. The results also showed that the SIFT algorithm provides the highest correct matching rate, and the SVAS method can be employed to resolve the parallax problems caused by stitching together images of different flat surfaces.

In this study, we proposed an alternative displacement sensor which constructed with reflection type holographic diffraction grating. To integrate with the truly phase detection heterodyne interferometer, and then the in-plane displacement can be measured with sub-nanometer displacement resolution. The smallest variation can be observed of proposed method is approximately 20 pm and there are no significant differences between proposed method and comparison methods. Furthermore, we evaluated the thermal property of the hologram and showed that the grating pitch variation is smaller than 0.1 nm for temperature variations within 1 °C. According to these findings, we can conclude that the holographic grating can be an alternative displacement sensor with high sensitivity and high stability.

Ceramics are commonly used as substrates in electrically insulated integrated circuit, printed circuit board, and lightemitting diode industries because of their excellent dielectric and thermal properties. However, brittle materials (e.q., ceramic alumina, sapphire, glass, and silicon wafer) are difficult to fabricate using wheel tools. Laser material processes are preferred over traditional methods because they allow noncontact processing, avoid tool wear problems, and achieve high speed, high accuracy, and high resolution. Laser material processes also exhibit minimal residual thermal effects and residual stress. This study investigated the laser drilling of Al₂O₃ ceramic material (with a thickness of 380 μm and hole diameters of 200, 300, and 500 μm, respectively) by using a laser milling method. The macro- and micro-hole milling performance depended on various parameters including the galvanometric scan speed and milling time. A 3D confocal laser scanning microscope and a field-emission scanning electron microscope were used to measure the surface morphology, taper angle, and melted residual height of the machined surface after laser milling. The edge quality and roundness of laser milling were also observed using image-processing edge-detection technology.

Demand for special optical components having the ability to concentrate and diffuse light effect has increased in order to improve luminance efficiency and function, relative to displays using micro lenses. There is a demand for design and machining technology for optical components that achieve various effects, among them the correction of light aberration and transmittance paths from aspherical surfaces with micro patterns. In this study, micro lens molds were machined that were able to simultaneously concentrate and diffuse light by means of lenticular patterns on aspherical surfaces. Two micro lens molds with micro lenticular pattern (pitch (P) of 10 and 100 μm) were machined on a sine type aspherical surface (amplitude (W) 0.15 mm and period (T) 3.0 mm). The micro lens molds were machined using an ultra-precision DTM (Diamond Turning Machine) and SSS (Slow Slide Servo). The micro lenses were replicated using PMMA resin; then light-transmission measurements were performed to confirm the effectiveness of the shape of various parts of the lenses on light-transmission. It was confirmed by measurement that concentration and diffusion light effects were simultaneously achieved.

Vehicular weight measurement while the vehicle is in motion has a significant application in traffic monitoring and weight regulation. While a conventional weighing scale requires vehicles to be sidetracked to a weighing scale, the current on-line system can provide a means of instantaneous measurement while the vehicle is moving. This would improve the throughput of heavily laden vehicles. The basis of this system is a Fiber Optic Polarimetric Sensor (FOPS) based on the principle of change in polarization of the light transmitting through the polarization maintaining (PM) fiber when subjected to external perturbation. The system is capable of static, transient and dynamic measurements. Circularly polarized laser light is coupled into the PM fiber, which is then subjected to the weight of the moving vehicle driven over it. The output from the photodetector is then displayed and analyzed using the software developed using LabView. The relationship between the weight of the moving vehicle and the wheel signature generated as vehicle passes over the pad is represented using a mathematical model. An accuracy of 86% in weight measurement of moving vehicles is achieved through this proposed system.

This research develops a precise hybrid optical micro-component (PHOMC) that includes polymer and glass materials. Although glass offers better anti-thermal, anti-environmental, anti-scraped, anti-corrosive, and optical properties than polymer materials do, glass materials are difficult to fabricate for microstructures. This research describes the fabrication of a PHOMC, which retains the advantages of glass materials; in addition, the cost of microstructure polymers is lower than for glass. In this study, polymers with micro sine waves can change the spot light intensity from a Gaussian distribution to a line with uniform distribution. The glass base can protect the PHOMC to avoid damage from the environment. First, the sine wave was designed using optical design software to change the light profile. A precise diamond-turning technique was used to fabricate a mold with a sine-wave profile. A glass plate was used for the base of the PHOMC. During the heating process, a thermosetting polymer was formed to match the sine-wave profile, and covered the glass base. The PHOMC is 10 mm in diameter, and a sine wave with 100 μm in amplitude and 6.283 in angular frequency was obtained. The surface profile of the PHOMC was evaluated using an ultra-precise laser confocal microscope. Processing parameters, such as the forming temperature, are discussed in this paper. The PHOMC with the sine wave that was developed in this study can generate a reference straight line for use in alignment, machine vision systems, construction, and process control.

Since the amount of data storage has kept growing, the transmitting rate of interface between data storages should be kept growing as well and the capacity of fiber-optic communication with single mode fiber become insufficient. Therefore, the multi-mode fiber which has much larger core diameter has been widely used in high data traffic application. The quality of end surface of fiber dominates the data transmitting efficiency. But the quality of cutting end surface which cut by the traditional mechanical fiber cleaving method was not good enough for the requirement of multimode fiber. In the recent year, the pulse CO2 laser was introduced to cleave the fibers. The optical system setup, laser pulse parameters, such as laser pulse energy, pulse width and number of laser pulse, will affect the quality of end surface of fiber. In this paper, the pulse CO2 laser fiber cleaving technology will be developed and the experimental setup will be introduced. And the relationships between the quality of cutting end surface and the cleaving parameters will be studied. The optimal laser control parameter set for fiber cleaving will be discussed as well.

The applications of AMLA (aspheric micro lens array) have been frequently required in opto-electro industries, such as optical communication, contact image sensor (CIS) module of scanner, wafer level optics, etc. In addition to the typical requirements of aspheric lens, for instance form accuracy and surface roughness, the pitch error of each micro lens has been highly required. Three ultra-precision freeform machining methods have been widely applied for the manufacturing of AMLA, namely fast tool servo, slow tool servo and diamond milling. UPDM (Ultra-precision diamond milling) have the advantage with no tool interference problem in comparison with tool servo machining techniques. In this paper, the tool setting error compensation method and the tool path of UPDM has been developed for the fabrication of a 5 by 5 AMLA model. The form accuracy and surface roughness of each lenses of the AMLA was less than 0.2μm and 5nm, respectively. And the pitch error of each micro lens was less than 2μm in 25 micro lenses.

Chalcogenide glasses (ChGs) have a relatively small temperature coefficient of refractive index, broad transmission range from almost visible to mid-infrared. It is suitable for precision molding. With the help of above mentioned merits, ChGs have a vast reservoir of value in the field of military and civilian infrared imaging. However, the internal defects of ChGs are caused by melting, cool-demoulding and annealing in a high vacuumed ampoule. The defects include the optical inhomogeneity, chemical inhomogeneity and built-in stress which trouble the homogeneity of ChGs and directly affect the imaging quality of infrared imaging devices. The detection and control of internal defects is a key technique. In this paper the platform for testing, characterization and evaluation of the inhomogeneity of ChGs will be designed and built. The appropriate testing and evaluation criteria of inhomogeneity during the preparation procedure of ChGs in the vacuumed ampoule will be studied. The transmittance of ChGs sample is measured repeatedly. The factor of internal multple reflection in ChGs sample is analysed and discussed. Analysis shows that the mean transmissivity of ChGs sample (Ge28Sb12Se60) with thick of 1 cm is approximately 66% in 8 to 11 microns. The loss is less than 2.40%/cm. The optical path difference (OPD) caused by residual stress in ChGs sample is less than 5.2 nm/cm. The results will provide a technical support to optimize the ChGs preparation process and improve the ChGs homogeneity.

In this work, we synthesized bulk amorphous GeGaS glass by conventional melt quenching technique. Amorphous nature of the glass is confirmed using X-ray diffraction. We fabricated the channel waveguides on this glass using the ultrafast laser inscription technique. The waveguides are written on this glass 100 μm below the surface of the glass with a separation of 50 μm by focusing the laser beam into the material using 0.67 NA lens. The laser parameters are set to 350 fs pulse duration at 100 KHz repetition rate. A range of writing energies with translation speeds 1 mm/s, 2 mm/s, 3 mm/s and 4 mm/s were investigated. After fabrication the waveguides facets were ground and polished to the optical quality to remove any tapering of the waveguide close to the edges. We characterized the loss measurement by butt coupling method and the mode field image of the waveguides has been captured to compare with the mode field image of fibers. Also we compared the asymmetry in the shape of the waveguide and its photo structural change using Raman spectra.

In order to have an efficient design methodology and achieve high-performance inertial instruments, it is important to analyze the dynamic characteristics of micromechanical vibratory gyroscopes. In this paper, a novel optical method based on a high-speed CMOS camera and different image recognition methods is developed to measure the translational motion of the sensitive elements. Experimental results show that digital image correlation (DIC) in the spatial domain is more accurate for determination of small displacements while quite time-consuming, and the mode of addition, subtraction or multiplication of spectrum images is much faster and provide more accurate results for determination of large displacements. Due to the edge features of images, the edge detection method based on wavelet is also proposed to calculate the displacements. This technique is quite fast and its precision is moderate. Accordingly, the combination of different image recognition methods will be more suitable for dynamic displacement measurements which require both high accuracy and high speed.

When light is stored in an optical fiber via stimulated Brillouin scattering (SBS) process, data-pulse from the storage to the restoration through two processes relates to acoustic wave, so the effects of an acoustic wave diffraction have to be considered. We numerically solve SBS coupled wave equations containing acoustic diffraction and study the effects of acoustic wave diffraction on stored light when the radius of fiber as storage medium is different. The results of light storage are obtained in the two situations presence and absence of acoustic wave diffraction when the control-pulse and the data-pulse have different temporal distribution profile. The results show that the acoustic diffraction influence on the light storage is more and more small with the fiber radius increasing, and when the fiber radius is 6 micron, the effects is disappear. The results also show that acoustic diffraction effects are minimum when data-pulse and control-pulse are rectangular and Gaussian distribution profile respectively.