Laser diode phase-shifting interferometer operating at a frame rate
Author(s):
Ribun Onodera;
Norio Onda;
Yukihiro Ishii
Show Abstract
We have developed a laser-diode phase-shifting interferometer that can capture frame-rate phase-shifted interferograms on a video tape with a high capacity of their storage. A number of the video frame is simultaneously recorded on an audio track of the video tape. The injection-current variation of laser diode in a four-step manner is synchronized with the field pulse of a CCD camera to produce (pi) /2-step phase shifts at a frame rate. An intensity distribution of the interferogram on any frame can be obtained from the video tape with a frame memory by utilizing the recorded frame number. The four successive phase-shifted interferograms are used to calculate a distribution of dynamic phase by a phase-extraction algorithm.
Improved phase unwrapping of a phase-shift interferometer using a precision XY-scanner
Author(s):
Sunglim Park;
Dae gab Gweon;
Kee S. Moon
Show Abstract
A phase shift interferometer with an improved phase unwrapping is presented. The nanometer resolution XY stage is integrated into the standard temporal phase shifting interferometer. The nanometer resolution XY stage is used to position specimen in subpixel of CCD detector, therefore CCD detector's sampling frequency is made high. This paper presents spatial sampling of CCD and two scanning algorithms, whose simulation and experiment results are also presented. The results show that the scanning algorithms make CCD detector's sampling frequency high, and phase unwrapping is improved also.
White light phase-shifting interferometry with self-compensation of PZT scanning errors
Author(s):
Seung-Woo Kim;
MinGu Kang;
SangYoon Lee
Show Abstract
One of main error sources in scanning white light interferometry is the inaccuracy of scanning mechanisms for which PZT piezoelectric ceramics actuators are widely used. In this paper, we propose a new calibration method being capable of identifying actual scanning errors directly by analyzing the spectral distribution of sampled interferograms. Experimental results prove that the method provides an effective means of in-situ self-calibration enhancing the measurement uncertainty by one order of magnitude.
High-sensitivity surface measurements by a heterodyne white-light interferometer
Author(s):
Akiko Hirai;
Hirokazu Matsumoto
Show Abstract
A novel low-coherence interferometer has been developed, based on the heterodyne technique for highly accurate and sensitive positioning of a three-dimensional (3-D) object, which uses two acousto-optic modulators (AOM's) and two spherical reflecting mirrors in a Michelson interferometer. By using this technique in a tandem interferometer, the profiles of diffusing and mirror-likes surfaces of the 3-D objects are measured with a high accuracy of 50 nm from the heterodyne signals of 200 kHz.
Wavelength scanning confocal interference microscope for separate measurement of refractive index and geometrical thickness
Author(s):
Takashi Fukano;
Ichirou Yamaguchi
Show Abstract
We previously proposed a system based on a combination of a confocal microscope and a wavelength scanning heterodyne interferometer, for separate measurement of refractive index and geometrical thickness of lens and plates. However, we used two optical systems successively although they share the same optical system. In this paper, we propose a new measurement scheme which enable us to measure both the confocal profile and the optical path difference of the interferometer by single scanning of an object. We describe herE the measurement principle, the apparatus, signal processing means, and some experimental results.
Dispersive coherence spectrotomography of a layered medium
Author(s):
Wataru Watanabe;
Kazuyoshi Itoh
Show Abstract
In low-coherence reflectometry, the light backscattered from a scattering medium is expected to carry information about the spectral properties as well as range information about the reflective boundaries and backscattering sites. We show two alternative techniques to extract both the range and spectral properties of the sample by optically dispersed interferograms. The methods make the most of the brightness of white-light continuum, which is generated by focusing ultrashort laser pulses into condensed matters. The output beam from an interferometer is dispersed by a spectroscopic optical element and the dispersed signal is detected by a line detector. The salient feature of the methods is that the spectral decomposition of the white-light interferograms enhances the dynamic range and signal-to-noise ratio. One method is a scanning type. By translating a sample, spectrally-resolved interferograms are detected. Appropriate grouping of the interferograms yields both range and spectral properties of the sample. The other method is based on the principle of spectral radar due to Hausler. The spectrally- resolved fringes are acquired without scanning. The signal- processing allows us to display both the scattering amplitude and spectral properties within the bandwidth of the filters. Experimental results will be presented.
Measurements of the effective optical constants and the flying height of read-write sliders by heterodyne inteferometry
Author(s):
JuYi Lee;
Der-Chin Su;
Cheng-Chih Hsu
Show Abstract
A new method for measuring the effective optical constants and the flying-heights with only an optical set-up by using the heterodyne interferometry is proposed. At first, a set of special equations for describing the relations among the phase differences of s-polarization with respect to p-polarization, the effective optical constants, and the flying-heights, are derived from the Fresnel's equations and the effects of multi- beam interferences. And the effective optical constants can be obtained from the conditions for the extreme points, which can be accurately determined with a heterodyne interferometer. Substituting the optical constants into the special equations which we derived previously, the flying-heights can be estimated.
Referenced polarization imaging for surface displacement measurements
Author(s):
Laura J. Ulibarri;
James K. Boger;
Matthew P. Fetrow
Show Abstract
A Referenced Polarization Imaging (RPI) method can be used to measure surface displacements in an uncontrolled environment without the use of complicated feedback and stability controls. The system is ideal for non-contact and nondestructive testing of parts or materials. Data can be acquired in a single frame, so that the effects of vibration are minimal. High resolution wavefront sensing is performed using polarization modulation instead of frequency shifting (which is necessary in a heterodyne detection system). A system for recording complex (amplitude and phase) images of coherently illuminated objects is described. The promise for this type of system is the ability to obtain digital complex images at real-time rates with simple hardware. These images can be digitally interfered on a standard PC to measure changes in the object at real-time rates. A simple RPI system is described and experimental results demonstrating performance are presented.
Birefringence measurement by scattered light method with a phase-shifting technique
Author(s):
Norihiro Umeda;
Jun Takahashi;
Daisuke Iiduka;
Hiroyuki Kohwa
Show Abstract
This paper describes a modified birefringence measurement using the scattered light method combined with a phase shifting technique. A phase shift between orthogonal linear polarization components is realized by a retardation compensator. The measured distribution has a periodical error, which can be reduced by a band pass filtering of the Fourier spectrum of scattered light distribution. This method enables a birefringence distribution on a light path to be obtained.
Heterodyne interferometers using orthogonally polarized and two-frequency shifted light sources with superhigh extinction ratio
Author(s):
Noboru Nakatani
Show Abstract
This paper describes the heterodyne interferometers using orthogonally polarized and two-frequency shifted light sources of two types with super-high extinction ratio for reducing non-linearity of the interferometer due to polarization cross- talk. The acousto-optic modulators are used for shifting light frequencies. In the first interferometer the light source with Glan-Thomson prisms of very high extinction ratio (50 dB) is used for making the polarization cross-talk very small. The Glan-Thomson prisms are put before the combiner of the polarizing beams. In the second interferometer the light source of frequency shifted beams with small crossing angle (2.5 mrad approximately 10 mrad) is used for excluding completely non-linearity of the interferometer due to polarization cross-talk. By measuring thickness of a vacuum evapolation film, it was demonstrated that the interferometers are useful to measure thickness of a thin film in nanometer order.
Combined measurement of shape and deformation of microcomponents by holographic interferometry and multiple-wavelength contouring
Author(s):
Soenke Seebacher;
Wolfgang Osten;
Chr. Wagner
Show Abstract
Progresses in microsystem technology promise a lot of new applications in industry and research. However, the increased complexity of the microsystems demand sensitive and robust measurement techniques. Full-field and non invasive methods are desirable to get access to material properties and parameters. This contribution describes a simple and fast technology for the analysis of shape and deformation of small objects by optical inspection. These quantities together with a defined loading of the components are the basis for the derivation of a variety of interesting material characteristics. The well known holographic interferometry and multiple wavelength contouring are precise enough to fulfill the requests for precision and resolution in microsystem technology even with structures of complex shape. Digital holography as the underlying holographic recording mechanism is extremely suitable for small objects and leads to simple and compact setups in which the objects' shape as well as their deformation behavior can be inspected. Several experiments are described and show the great potential of these fast and robust measurement techniques.
Adaptive speckle pattern interferometry
Author(s):
Janos Kornis;
Zoltan Fuzessy;
Attila Nemeth
Show Abstract
In our paper we have analyzed the application possibility of a modified version of speckle pattern interferometry: the adaptive speckle pattern interferometry (ASPI). The peculiarity of this technique is that reference waves are produced by holographically reconstructed virtual images. Using this course an adaptive measuring system can be built. A realization of the ASPI is presented as a measuring device for various measuring tasks. Selected applications are shown from real time holography to comparative displacement measurement.
Stereovision setup for accurate 3D deformation measurements
Author(s):
Per Synnergren
Show Abstract
The system described uses a digital image correlation technique called Digital speckle photography (DSP) for the measurement of 3-D surface deformations. A stereoscopic technique with two perpendicular video cameras was developed to enable accurate measurements on arbitrarily shaped objects. Using the calibration algorithm described the main source of error are random errors originating from the correlation algorithm. Standard deviations of displacements as low as 2 micrometer for in-plane displacements and 12 micrometer for the out-of-plane component are reported, for an inspected area of 100 X 100 mm2.
Industrial applications of residual stress determination using 2D in-plane sensitive fiber ESPI and hole drilling
Author(s):
Anand Krishna Asundi;
Jingbo Zhang
Show Abstract
A fiber electronic speckle pattern interferometry (ESPI) system composed by two sets of Leendertz dual-beam illumination arranged in perpendicular directions is applied to determine residual stresses of materials combining with the blind-hole-drilling method. Although high stress concentration and severe surface decorrelation resulted from hole-drilling process would affect the fringe visibility considerably, the system still generates satisfactory fringe patterns from the point of view of data retrieval. Simple approaches to interpret values of uniaxial and uniform residual stresses from displacement sensitive fringe contours are described and demonstrated for industrial applications.
Whole-field speckle strain sensor
Author(s):
Mikael Sjodahl
Show Abstract
The construction of a whole field speckle strain sensor is reported. The sensor makes use of the in-plane motion of defocused laser speckles in a telecentric imaging system. To distinguish between the contribution to the speckle motion from surface displacement, strain, rotation and tilt three different illumination directions were used. For illumination three pigtailed laser diodes of slightly different wavelength was used. To allow for simultaneous acquisition of the three speckle patterns, the different wavelengths were splitted with the aid of dichroic mirrors and directed onto separate synchronized detectors. The motion of the three speckle patterns is calculated using digital speckle photography and combined to give the three in-plane components of the strain tensor. A discussion about sources of random and systematic errors are included.
Laser speckle interferometry for welding inspection
Author(s):
- Suprapedi;
Rini Widiastuti;
Satoru Toyooka
Show Abstract
Degradation processes of welded materials from the beginning of tensile until fracture were investigated by laser speckle interferometry (LSI). In the LSI system, speckle patterns are acquired continuously by a CCD camera while the tested object is deformed. A series of speckle correlation fringe patterns are obtained by subtracting couples of two interfering speckle patterns while the reference speckle patterns are renewed successively. The localized strain can be identified occasionally as the remarkably white band (WB) or irregular patterns in the correlation fringe patterns. The behavior of deformation on the specimen surface was visualized on a video monitor as moving correlation fringe patterns. In the experiment of welded specimens, the WB or irregular fringe patterns due to the localized deformation was observed for the first time at the welding part of the specimen in the elastic stage of deformation. The position of the WB was stationary although the loading progresses. Finally the specimen fractured at the position of the WB or the location of the welding. The LSI system is expected to be applicable to identify defect in the solid materials.
Measurement for thickness variation of a latex membrane by ESPI method
Author(s):
Anand Krishna Asundi;
Lijun Jiang
Show Abstract
A simple and unique ESPI based system for real-time monitoring and measuring of thickness variation of semi-transparent membrane with an 'optically rough surface' is described in this paper. When membrane or film is illuminated by a coherent beam, a speckle pattern is produced on its rough surface. Reflected beams from both the bottom and top surfaces of the membrane combine and form a speckle interferometric pattern, which can be captured by CCD camera. Subtraction of sequentially captured images result in correlation fringes corresponding to thickness variation of the specimen. The beams reflected from both bottom and top surfaces serve as 'reference' beam for each other mutually. All the beams coming from the tested object possess an auto-reference feature and this makes the system more stable and simple.
Sinusoidal phase-modulating laser diode interferometer using photothermal modulation
Author(s):
Takamasa Suzuki;
Mineki Matsuda;
Osami Sasaki;
Takeo Maruyama
Show Abstract
A laser diode interferometer that uses accurate photo-thermal modulating technique is proposed. Since this technique of photo-thermal method modulates just a wavelength of the laser diode, measurement accuracy is not affected by an intensity modulation that is used to be appeared in the current modulation. The fundamental characteristics of this technique is investigated in detail. The new setup is tested, and its accuracy compared with that of an earlier system.
Direct distributed velocity sensing using a low-coherence interferometer
Author(s):
Yoh Imai;
Kazuhiro Tanaka
Show Abstract
A new distributed sensing method for measuring directly the flow velocity by using low coherence interference techniques is proposed and demonstrated. In the present method, temporally fluctuated signal, not the Doppler frequency shift, is detected. Theoretical analysis shows that the spectrum of backscattered light from the particle takes a Gaussian form whose width is simply proportional to the flow velocity. The accuracy for adjusting the depth position is approximately 34 micrometer which is determined by a coherence length of a light source.
Optoelectronic interferometric vibration sensor
Author(s):
Chandra Shakher;
A. L. Vyas;
V. S. Rawat
Show Abstract
An opto-electronic sensor for monitoring/measurement of vibration based on interferometry is presented. A modified Michelson interferometer is used to process the signal received from the sensing (fiber) interferometer. In this paper we present a new signal-processing scheme for interferometric vibration sensor which can be also used to monitor localized strains and vibrations. For the real time monitoring of vibration parameter the sensor is interfaced with PC.
Shadow moire profilometry using a phase-shifting method
Author(s):
Lianhua Jin;
Yutaka Kodera;
Toru Yoshizawa;
Yukitoshi Otani
Show Abstract
In order to measure 3-D surface of objects by using phase- shifting method, based on shadow moire topography, two stages are planned. The stages are moving the grating vertically, which produces a change in moire pattern; rotating the grating, which results in the constant phase-shift regardless of the moire fringe order. The paper emphasis is on describing the novel method, and justifying it by error simulation test. The experimental results show that this technique is available for some industrial fields.
Three-dimensional surface measurement using grating projection method by detecting phase and contrast
Author(s):
Mitsuhiro Ishihara;
Yasuo Nakazato;
Hiromi Sasaki;
Masahito Tonooka;
Masayuki Yamamoto;
Yukitoshi Otani;
Toru Yoshizawa
Show Abstract
A grating projection method using a stereomicroscope is developed to provide a surface profile measurement. The phase shifting technique is applied for high accuracy detection of the projected fringe. To overcome 2(pi) phase jump caused by large step in height and to detect absolute height from the fringe number, contrast detection of the projected pattern is available. The contrast varies in relation with the distance between the sample and the objective lens. This variation is almost as same as optical sectioning that is usually used in confocal microscopy. The fast reconstruction procedure is proposed to analyze the focal point from a few images. This method is demonstrated and conformed to measure the steep surface profile of a test sample.
Residual stresses in unsymmetric laminated carbon fiber composites
Author(s):
Yu Liu;
Meng Yin Quek;
Anand Krishna Asundi
Show Abstract
The laminate is constructed so that symmetry about the midplane is not maintained. Upon cooling from the cure temperature, certain plies contract more than their neighbors, inducing residual stresses in this cross-ply laminate. Residual stresses coupled with asymmetries in the laminate produce warpage. Laminated plate theory is used to calculate the residual stresses and warpage. Also, residual stresses are related to the strains released when the hole-drilling technique is applied. In the experiment, high-sensitivity moire interferometry is used together with the hole-drilling method to determine the residual strains. The theoretical and experimental results are in qualitative agreement.
New error-compensation method in a linear encoder using phase-shifted grating
Author(s):
Ju Ho Song;
Kyung-Chan Kim;
Soo Hyun Kim;
Yoon Keun Kwak
Show Abstract
A new hardware compensation method reducing displacement measurement errors, caused by tilt of index scale in moire type linear encoder, has been developed. In the conventional moire type linear encoders, the detectors are aligned perpendicular to the line of moire fringes and this structure is very sensitive to an unwanted tilt of the gratings. In this paper, newly designed grating, named as phase shifted grating, is developed to compensate non-orthogonal error. By adopting the phase shifted grating instead of conventional index one, it is possible to reduce non-orthogonal error of the moire type linear encoder.
High-performance encoder using the encoder model in a computer
Author(s):
Yuji Matsuzoe;
Koetsu Fujita;
Nobuhiko Tsuji
Show Abstract
We propose the analysis system and technique for the optical encoder which does not require an analysis of the incoherent light and the diffraction. This system is composed of an LED, a rotation disk, a CCD camera to detect the light intensity for which to transmit a rotation disk, and the photo detector model in the computer, it receives the same output signal as the real encoder. The optical system of the encoder is optimally designed by this analysis system and technique, and then, this high resolution encoder which has the resolution of 100 times and more than the conventional impulse wave encoder is realized.
Compact optical encoder using modulated-pitch phase grating: suppression of harmonic noise and contrast change
Author(s):
Atushi Ieki;
K. Matsui;
M. Nashiki;
Kazuhiro Hane
Show Abstract
In this paper, we investigate the combination of two gratings for a compact optical displacement encoder. The modulated pitch gratings are considered to obtain the sinusoidal signal as a function of displacement. In addition, the phase grating with the pitch modulation is examined to suppress the contrast change of the encoder signal as a function of the gap between the index and main scales. By these investigations, we find some combinations of gratings to satisfy the above requirements.
Rotation angle measurement using an imaging method
Author(s):
Takamasa Suzuki;
Hideki Nakamura;
John E. Greivenkamp;
Osami Sasaki
Show Abstract
A system of rotation angle measurement based on the fringe projection is proposed and demonstrated. This system has potential for a broad range of uses and a robustness for the external disturbances, because it requires no coherent light. The setup is very simple and applicable to the automatic on- line measurement. Several measurements indicate a sensitivity of 5 arcsec.
Independent component analysis based on a scatter diagram
Author(s):
Katsuhisa Hirokawa;
Taro Yamaguchi;
Kazuyoshi Itoh
Show Abstract
We propose a novel algorithm for the independent component analysis that reshapes a scatter diagram or the joint probability density function of the pixel values of the mixed signals. The detailed procedure of the algorithm is described and its performance is numerically evaluated. The present algorithm geometrically separates original independent images from mixed images by the linear transformation, in which shift, shearing and rotation are performed to the scatter diagram. After the transformations and normalizations, the basis vectors of the independent signal become orthogonal and match the coordinates. In the implementation, it is shown that the algorithm can decompose two independent images from two mixed images. In additions, the proposed algorithm are compared to two conventional algorithms; [G. Burel: Neural Networks 5, 937 (1992)] and [A. Hyvarinen and E. Oja: Neural Comp. 9, 1483 (1997)], in calculation speed and extraction accuracy.
Ultrasound-assisted optical measurement for observation inside a scattering medium
Author(s):
Masaki Hisaka;
Tadao Sugiura;
Satoshi Kawata
Show Abstract
We have developed an optical measurement method to investigate the inside of scattering media by using focused ultrasound to specify the measuring point. This method enables us to observe the internal structure of human tissue non-invasively for biomedical applications. This method may give us various kinds of material information such as spectroscopic characteristics. To get the information from only particular region in a tissue sample with light, we use a focused ultrasound. At the focal region of the ultrasound, refractive index of the tissue changes with strong acoustic field. So a part of incident light reflects at the focal region of the ultrasound. The reflected light has information of the sample. According to the scanning of the sample, we can get an image of the sample. In our experiments, we have observed samples that consist of an agarose block which contains a piece of agarose cube stained with dye as absorbing material. The intensity of reflected light from the focal region of the ultrasound decreased when the measuring point was in the stained agarose section, because incident light was absorbed with the dye. Furthermore, we have observed a sample with a weak scattering object made of agarose in strong scattering agarose that contains PMMA particles.
Angular correlation properties of multiply scattered light in random media with buried objects
Author(s):
Suguru Sangu;
Takashi Okamoto;
Jun Uozumi;
Toshimitsu Asakura
Show Abstract
Effect of objects buried in highly dense media on the properties of angular intensity correlation of the scattered light is investigated by means of a theoretical approach and numerical simulations. In the case of an object located just behind the scattering medium, a Fourier transform relation between the angular correlation function and the intensity distribution in the illumination plane where the object exists is derived theoretically for transmitted light. When the object is buried in the medium, such a boundary condition is not satisfied, and it was found from the simulation results that the effect of the object on the angular correlations can be observed more strongly for the object being somewhat deep rather than near the output surface. For reflected light, on the other hand, the influence of the object on the angular correlation function becomes small because of a scattering component not reaching the object.
Scattering characteristics of Si3N4 mixture surface under laser illumination
Author(s):
Wen Qing Liu;
Hiroaki Kuze;
Nobuo Takeuchi
Show Abstract
Scattering characteristics of metal surfaces sprayed with Si3N4 nano-powder and plastic powder mixture were evaluated by an angle-resolved reflectometer. The preliminary results obtained seem to indicate that the characterization of the angle-resolved scattering distribution can be controlled as needed by selecting the sample surface material and/or its mixture. The property may be used in analysis of surface signatures. The relation between the angular distribution of scattering-cross section and the statistical characteristics of random height of microrough metal surface is also discussed in this paper.
Plastic-fiber-bundle-based metrology for two-dimension mapping of the dissolution rate of photoresist film
Author(s):
Gong-Ru Lin
Show Abstract
A multi-port plastic-optical-fiber-bundle-based metrology is demonstrated for dynamically monitoring the thickness variation and or dissolution rate of photoresist film during photolithography process. The homemade plastic fiber bundle exhibits different structures at each end connecting to optical source, end-point probes and optical receivers, which excludes the needs of beam splitters and mirrors. Experimentally, the dissolution process of the AZ1350 photoresist film at several different sites on a 4-inch silicon wafer was dynamically monitored. The dissolving rate of the photoresist film was simultaneously estimated from the measured time-resolved optical interference pattern that reflected from the sample surface. The deviation on thickness of photoresist film estimated by using current apparatus were compatible with that estimated by using commercial ellipsometry. Furthermore, a two-dimensional mapping of thickness-contour of a dissolved photoresist film is also illustrated. The POFB-based probe can further gain the benefits such as anti-acid, lower loss in visible light region as compared with the silica-fiber-based one. As the fast evolution IC technology, real-time/multi-port monitoring the transient variation on thickness of thin organic (or dielectric) film during micro-lithography and etching processes by using this system is straightforward.
Spectrum-enhanced correlator by two-wave mixing in a photorefractive crystal
Author(s):
Takeshi Takahashi;
Yukihiro Ishii
Show Abstract
A real-time spectrum-enhanced correlator has been constructed to improve the correlation performance. The system in a photorefractive BaTiO3 two-wave mixing plays a role to enhance the optical spectrum of an input object at a Fourier domain by changing the pump beam intensity. Coherent enhancement together with a phase-only filter can be achieved a good correlation performance. The character-recognition experiments with the system are shown.
Neural-network-based analysis of photoelastic color using a spectral synthesizer
Author(s):
Wenjun Wang;
Satoru Toyooka;
H. Nozawa
Show Abstract
Spectral distribution of photoelastic color have direct relationship with difference of principal stresses. Spectral distributions corresponding to known stress values are measured and used as learning data of unsupervised neural network. Optimal filter functions are designed by an unsupervised neural network. The learning data is also used as a scale for recognition of spectral distribution of unknown stress. Photoelastic sample under different stresses is illuminated by the light generated by a spectral synthesizer which consist of dispersing system including liquid crystal spatial light (LCSLM) modulator. By controlling the transparency of LCSLM modulator using supervised neural network, several the illuminating light are made so that their spectral distribution are same with filter functions and they are used as the light source photoelastic interferometer. From intensities recorded, spectral distributions are calculated. Stresses are estimated by comparing recorded intensities with scale made from learning data.
Open, intelligent, and scalable optical part-recognition system
Author(s):
Walter van Dyck;
Thomas Berndorfer;
Alexander Werner Brenner;
Zsolt Tamasi
Show Abstract
In production and assembly processes, part-recognition is an important task in the field of quality assurance, determination of position errors and sorting of the inspected parts. The benefits and the conditions of part-recognition vary in a wide range, which led to the availability of numerous systems based on different technologies. Depending on the problem which has to be solved you have to compare the several technologies and to choose the systems which solves the given problem best. For example mechanical separation has their great power in robustness and throughput rate. But depending on geometry of the parts such system can be very complex. Furthermore an additional disadvantage is the fact that its not easy to detect lacks of quality. In the worst case such a defective part can cause a destruction of the assembly machine. If high flexibility or better accuracy is requested, other technologies like an optical system have to be used. The selection of an appropriate, cost-effective system is a very difficult and time-consuming task. If it is decided to use an optical system then in many cases a special system has to be constructed. Our approach is not to develop a further system for a special problem, but to provide a system for various applications. Therefore our demands for such a system are that it is open, scaleable and intelligent.
Using field bus for optical gas monitoring
Author(s):
Xiangyin Cheng;
Leong Keey Seah;
Lin Seng Ong;
Anand Krishna Asundi
Show Abstract
This paper presents a proposal for an optical gas monitoring system based on fieldbus. With the help of the advanced signal processing system more than one hundred gas detectors can be connected to a host system by a single shared bus cable over which the gas detectors, now incorporating with their own intelligence, communicate digitally with the host system. The new system supplies not only about the gas level but also about the physical condition of each sensor. Planed maintenance can be performed to ensure that gas monitor system is maintained in full working order. Integrating fieldbus with optical gas sensor will also have dramatic saving in field wiring and the man-hours for system verification and configuration.
Fiber optic spectrophotometry monitoring of plant nutrient deficiency under hydroponic culture conditions
Author(s):
Oi Wah Liew;
William S. L. Boey;
Anand Krishna Asundi;
Jun-Wei Chen;
Duo-Min He
Show Abstract
In this paper, fiber optic spectrophotometry (FOSpectr) was adapted to provide early detection of plant nutrient deficiency by measuring leaf spectral reflectance variation resulting from nutrient stress. Leaf reflectance data were obtained form a local vegetable crop, Brassica chinensis var parachinensis (Bailey), grown in nitrate-nitrogen (N)- and calcium (Ca)- deficient hydroponics nutrient solution. FOSpectr analysis showed significant differences in leaf reflectance within the first four days after subjecting plants to nutrient-deficient media. Recovery of the nutrient-stressed plants could also be detected after transferring them back to complete nutrient solution. In contrast to FOSpectr, plant response to nitrogen and calcium deficiency in terms of reduced growth and tissue elemental levels was slower and less pronounced. Thus, this study demonstrated the feasibility of using FOSpectr methodology as a non-destructive alternative to augment current methods of plant nutrient analysis.
Optical monitoring of the concentration profile of submicron latex particles in flow through a translucent water-permeable tube: demonstration of flow-dependent concentration polarization of plasma
Author(s):
Shigeo Wada;
Toshiaki Iwai;
Takeshi Karino
Show Abstract
It is well accepted that hemodynamics plays an important role in atherogenesis in man. However, the precise mechanisms have not been elucidated yet. Recently, Karino and his coworkers hypothesized that flow-dependent concentration polarization of low-density lipoproteins (LDL: a carrier of cholesterol) may occur at a blood/endothelium boundary, leading to a high risk of atherogenesis in regions of slow flow and low wall shear rate where the concentration of LDL builds up. In this study, we attempted to confirm experimentally their predictions by measuring optically the concentration profile of polystyrene microspheres (used as a model of LDL) flowing in steady flow through a dialyses tube (used as a model of an artery) by transversing a laser beam across the tube and detecting the intensity of the transmitted light. It was found that surface concentration of the microsphere certainly increases with decreasing the flow rate (hence wall shear rate) and it occurs even under the conditions of a very low water filtration velocity encountered in normal arteries in vivo, thus giving a strong support to the hypothesis proposed by Karino et al.
Optical remote sensing information modeling for monitoring rural land use
Author(s):
Zesheng Zhu;
Ling Sun
Show Abstract
This paper provides a discussion of principles and concepts of optical remote sensing information modeling for monitoring rural land use as contained in the monitoring information model. The model has emerged as an object-oriented paradigm for the modeling rural land systems and resources for monitoring rural land use. The model is designed to meet the needs of rural land users, providers and managers with optical remote sensing information. By using the above modeling principles and optical remote sensing information, it has been possible to develop a rural land use monitoring model powerful and flexible enough to meet rural land use monitoring requirements expected in the 21st century.
Oxy-fuel combustion emission monitoring using tunable diode laser sensors
Author(s):
William A. Von Drasek;
David M. Sonnenfroh;
P. Keating;
Mark G. Allen;
Olivier Charon
Show Abstract
With stricter environmental regulations, optimization of the combustion process for reduced pollutant emission and higher fuel efficiency has become an industry objective. To achieve these objectives, continuous monitoring of key processes parameters such as temperatures, fuel and oxidant input, and flue gas composition is required. For flue gas composition monitoring conventional extractive sampling techniques are typically used. However these techniques suffer from slow response time due to long sample lines and are sensitive to plugging problems when applied to particle-laden flows. Using in-situ monitoring with near-IR tunable diode lasers (TDL) eliminates the problems encountered with extractive sampling. The chemical species to be monitored dictates the wavelength range of the diode lasers used. These lasers are rapidly tuned over an absorption line to obtain concentration along the line-of-sight path. In addition, gas temperature can be measured by scanning the laser over multiple rotational lines of a target molecule. Here we demonstrate the feasibility of using TDL's for in-situ O2 monitoring on the exhaust end of Air Liquide's oxy-fuel pilot furnace. Tests were conducted at various operating conditions and compared with conventional extractive sampling measurements. The response time of the technique is demonstrated by measurements conducted on a dynamic system where the fuel flow is oscillated at low frequencies. In addition, to study the effect of dirty gas streams typically found on industrial processes, seed particles were introduced into the burner to simulate particle-laden flows.
Spectral measurements of two-dimensional color images
Author(s):
Markku Hauta-Kasari;
Kanae Miyazawa;
Satoru Toyooka;
Jussi P. S. Parkkinen
Show Abstract
In this work we propose a prototype of the spectral vision system, which can be used to measure a color spectrum and two- dimensional spectral images. We first designed a low- dimensional broad band color filter set with a constraint of positive spectral values by the unsupervised neural network. Then we constructed a compact size optical setup for the spectral synthesizer, which can be used to synthesize the light corresponding to the spectral characteristics of the color filter. In the optical setup we implemented the color filters by the use of the liquid crystal spatial light modulator (LCSLM). In our experiments we illuminated a sample of a real world scene by the synthesized lights and detected the intensity images of the filtering process by the CCD- camera. The intensity images correspond to the optically calculated inner products between the color filters and a sample. The data obtained from the filtering process is only a few monochrome images and therefore convenient for storing and transmitting spectral images. From the detected inner products we reconstructed the sample's color spectra by the use of inverse matrix. We present experimental results of measuring a single color spectrum and two-dimensional spectral images.
Intelligent optical sensor concept: a new approach using interconnecting sensors
Author(s):
Thomas Berndorfer;
Dieter J. Schmidradler;
Alexander Werner Brenner;
Walter van Dyck
Show Abstract
The possibility of connecting sensor and actuator systems to complete networks has led to new hardware/software structures in industrial applications. Smooth integration of high bandwidth optical sensors and devices into such systems was an almost impossible task due to problems of interfacing optical components to available bus systems with transfer rates below 1 Mbit/s. Attempts are going on to build up high bandwidth deterministic bus systems that deal with enormous data rates e.g. given by visual sensors like cameras. This would lead to even worse problems in processing all the data in central computing units. This paper introduces a new concept of how to connect high data rate optical devices to currently available low cost bus systems. The concept is based on dramatically reducing data rates by supplying sensor/actuator peripherals with their own adequate computing power. Raw data transfer is replaced by doing intelligent communication within the interconnecting network on a higher level of abstraction. Computing power moves into periphery making raw sensors intelligent ones. The paper shows that the system of interconnected intelligent sensors offers a high degree of efficiency, flexibility in connecting the parts together and scalability in a natural manner. The paper figures out that integration of optical high bandwidth devices into networking systems is no longer impossible. The reduction to an absolute minimum of communication effort allows the usage of cheap well known bus systems which leads to high acceptance in industry.
Remote sensing analysis of surface water in a mining area
Author(s):
Han Zhen;
Fengjie Yang;
Xianghua Feng;
Jiwei Liu;
Yong Qing Li;
Liqing Lei
Show Abstract
The exploitation of the coal has brought about pollution on the surface water. That was seriously harmful to environment. Thinking of the Feicheng mining area as research area, authors tested the reflectance spectrum of waters and analyzed these curves. The paper made the computer image processing by TM computer compatible tape. Combining routine monitoring methods and TM images, the surface water of mining area was comprehensively analyzed furthermore. This paper provided a rapidly and economical method of monitoring mining area surface water.
Planar binary optical see-through visor design
Author(s):
Liping Zhao;
Yee Loy Lam;
Yan Zhou;
Zhisheng Yun;
Wenxiu Que
Show Abstract
A novel planar-binary optical see-through visor, in which three binary optical elements, namely two couplers and one compensator, are designed to be fabricated on a planar glass slide substrate, is presented in this paper. One binary focusing coupler serves to image and couple the light into the optical plate so that the light can travel within the planar passage via total internal reflection. The other coupler directs the light out of the plate, and the compensator makes it possible for the user to see directly through the visor at the same time. Harmonic diffractive technology is employed to reduce the chromatic displacement in the visible range. The schematic of the structure and simulation results are given in this paper. Our results indicate that it is promising to utilize the planar-binary optics to cover the visible band.
Optimization design of diffractive optical elements by genetic local search algorithms
Author(s):
Guangya Zhou;
Xiaolin Zhao;
Zongguang Wang;
Yi-Xin Chen;
Mingsheng Zhang
Show Abstract
In this paper, a novel optimization algorithm, termed genetic local search algorithm (GLSA), that combines a genetic algorithm (GA) with a local search technique is proposed to design DOE's. This hybrid algorithm performs an improved, more goal-oriented search compare to a purely GA. A 1:17 cross pattern fan out grating and a uniform focal plane intensity profile generator are designed to demonstrate the algorithm we proposed. Numerical results proved that the proposed algorithm are highly robust and efficient. High-quality DOE's are achieved by using the algorithms we proposed.
Fabrication of multilevel diffractive elements in SiO2 by electron-beam lithography and proportional etching
Author(s):
Pasi Laakkonen;
Jari Lautanen;
Janne Simonen;
Jari Pekka Turunen;
Veli-Pekka Leppanen;
Timo Jaaskelainen
Show Abstract
A new negative low-contrast electron beam resist X AR-N 7700/18 is used in multilevel structuring with direct electron beam exposure. The developed multilevel resist profiles are transferred into SiO2 substrates with reactive ion etching (RIE) and the desired profile depths are achieved by a proper adjustment of the pressure during the etching process. The tolerance of profile depth errors is found to be less than 2.5%. Examples of multilevel pixel-structured gratings and diffractive lenses are given.
Diffractive optical element array to realize uniform focal spot with any geometrical shape transform
Author(s):
Qiaofeng Tan;
Yingbai Yan;
Guofan Jin;
Minxian Wu
Show Abstract
Uniform focal spot which has top flat, steep edge, low sidelobes and other features is needed in many fields, such as Inertial Confinement Fusion and laser manufacturing. For different application, different input conditions and output demands are requested, for example, the laser put in or/and uniform focal spot put out has any kinds of geometrical shape, including circular, square, elliptical and so on. Such uniform focal spots with a certain geometrical shape transform can be realized by using Diffractive Optical Elements (DOEs) array, which has many advantages, such as high light efficiency of the pure phase modulation, strong flexibility of the phase design and geometrical shape transform and so forth. Hybrid algorithm based on hill-climbing and simulated annealing is utilized for phase design because of the ability of strong convergence of the hill-climbing and the global optimization potential of the simulated annealing. Geometrical shape transform is based on the principle of any geometrical shape can be approximated to by some series of square cells with different positions, different or same sizes. The phase design is simplified by adopting square cells, because two- dimensional problem is converted to one-dimensional problem. Two typical cases are concerned, i.e. circular laser put in with square uniform focal spot put out and square laser put in with circular uniform focal spot put out. Simulated results show this method and the hybrid algorithm are very valid. 6
Narrowband holographic spectral filters: principles, manufacturing, and applications
Author(s):
Irina V. Semenova;
Nadya O. Reingand;
Alexander Popov
Show Abstract
In this paper we present an analysis of hologram parameters required to obtain an extremely narrowband holographic spectral filters, operating in reflection configuration. The spectral selectivity of such gratings is calculated as a function of the layer thickness and the recording geometry. The experimental results on the recording of spectral filters in photopolymer with diffusive amplification are presented. The current and potential applications are discussed.
Diffractive-optics-based sensor for simultaneous inspection of reflected and transmitted light from porous materials
Author(s):
Raimo Veil Johannes Silvennoinen;
Paul Wahl
Show Abstract
Optical reflectance and transmittance of porous material carry information from a surface smoothness and a bulk porosity of a sample. Thus it is of great importance to get simultaneously optical signals connected with the reflected and transmitted light from a porous sample. Previously we have showed that a diffractive optical element (DOE) based sensor is capable to distinguish optical signals, when a scattered wavefront from a sample surface is diffracted through a DOE-aperture, with good agreement compared with the values drawn out by a conventional spectrophotometer. The aim of this paper is to present a DOE based sensor for simultaneous inspection of reflected and transmitted light from porous materials, which are e.g. wood, paper, and pharmaceutical compacts.
Improvements of quantized kinoform reconstruction by changing the position of the desired image
Author(s):
Shiyuan Yang;
Teruo Shimomura
Show Abstract
It is well known that the off-axis kinoform reconstruction has low reconstruction errors than the on-axis one. We analyze the dependence of kinoform reconstruction on the position of the desired image by use of a bias limiter model. It is found that the reconstruction error of kinoforms changes periodically as the desired image position changes, and the reconstruction error of low quantized kinoforms can be reduced by shifting the desired image position away from the optical center when the size of the kinoform input is larger enough than that of the desired image.
Diffractive optical concentrator for an infrared detector
Author(s):
Chunlei Du;
Chuankai Qiu;
Qiling Deng;
J. Z. Zhao;
D. J. Yang;
L. B. Bai;
Hongjun Zeng
Show Abstract
In this paper, a method for improving the performance of unit infrared detector has been proposed. An experiment was carried out by putting micro-concentrator in front of the tested detector, micro-concentrators are diffractive microlens with different numerical aperture (N.A.) which were obtained by special design and fabrication. The performance has been evaluated for the coupled detector and compared with the simulation.
Holographic optical elements with high spectral and angular selectivity
Author(s):
Nadya O. Reingand;
Irina V. Semenova;
Alexander Popov
Show Abstract
It is well known that very thick volume holograms both transmission and reflective type being illuminated by light indicate very high angular (less than milliradian) and spectral (less than nanometer) selectivity. Such highly selective holograms can find wide application in different fields. The variety of diffraction elements: filters, angular and spectral selectors, etc. can be designed basing on very thick holograms. The main problem in manufacturing of thick holograms (of about millimeter thickness) is in developing of very thick photosensitive media, in which this grating can be recorded without shrinkage and distortions. The overview of Russian materials suitable for the recording of thick volume holograms is made in this paper. We demonstrate the experimental results of the recording of high efficient (90%) transmission angular selector (with the selectivity bandwidth of about milliradian) and reflection spectral selector (bandwidth of about nanometer) using PDA material (photopolymer with diffusive amplification). Such very high selective optical elements can find application in spectroscopy, space communication, lidar sensing, wavelength demultiplexing, optical storage, and others.
Pigtail-type CO laser using As2S3 optical fiber
Author(s):
Satoshi Tanaka;
Yuzoh Setoguchi;
Mitsunori Saito;
Heihachi Sato
Show Abstract
Inserting an As2S3 optical fiber into a coupling-hole of one of the optical resonator mirrors directly, a pig-tail type CO laser is successfully demonstrated on its fundamental operational characteristics, together with theoretical treatments. First, finding the spatial intensity-distribution on the coupling-hole mirror, its effective transmittance vector t is evaluated in comparison with the measured spatial beam profile. Then, the output power is measured with the various coupling-hole mirrors, obtaining the maximum output power at the coupling-hole diameter of approximately 0.6 mm. These characteristics of the output power vs the coupling-hole diameter are theoretically explained by using the gain parameters G and the internal loss vector ai obtained, being well consistent with the experiments. As a result, the optimum coupling-hole evaluated is quite suitable to compose the pig-tail type scheme.
Multipoint detection of an acoustic wave in water with a WDM fiber-Bragg-grating sensor
Author(s):
Nobuaki Takahashi;
Kanta Tetsumura;
Sumio Takahashi
Show Abstract
Using two fiber Bragg gratings (FBG) in serial connection and WDM technique, multipoint detection of an acoustic field in water is demonstrated after having measured the spatial resolving power of an FBG underwater acoustic sensor. An acoustic sensor with a 24 mm ling FBG is found to have the spatial resolution on the order of 1 mm. Two FBGs in the WDM sensor work independently without interfering each other and the sensor provides us with real-time detection of the amplitudes and phases of the acoustic field at different points in water.
Optical wavelength switch using strain-controlled fiber Bragg gratings
Author(s):
Hiroyuki Uno;
Akiyoshi Kojima;
Atsushi Shibano;
Osamu Mikami
Show Abstract
Fiber Bragg gratings have been studied intensively these years, because of their high potentiality in being applied in wavelength division multiplexing fiber transmission systems. As one of their useful characteristics, Bragg reflection wavelength can be changed by applying stress to the grating region. We obtained a maximum wavelength shift of 6.08 nm at 300 electric pulses to an electrically-driven micro-step stage. We investigated its possibility of optical wavelength switching. We achieved maximum extinction ratios of 26.0 dB and 25.9 dB for reflected and transmitted lights, respectively, and realized a switching time of 8 - 10 msec.
Fiber optic Bragg grating sensors for hydrogen gas sensing
Author(s):
Boonsong Sutapun;
Massood Tabib-Azar;
Alex A. Kazemi
Show Abstract
We report a new type of optical hydrogen sensor with a fiber optic Bragg grating (FBG) coated with palladium. The sensing mechanism in this device is based on the mechanical stress that is induced in the palladium coating when it absorbs hydrogen. The stress in the palladium coating stretches and shifts the Bragg wavelength of the FBG. Using FBGs with different wavelengths many such hydrogen sensor can be multiplexed on a single optical fiber. Operation of two multiplexing sensors is demonstrated. Moreover, hydrogen and thermal sensitivities of the senors were measured and calculated using a simple elastic model. Moreover, to quantify the amount of stress in the palladium film as a function of hydrogen concentration, a novel and very sensitive method was devised and used to detect deflections in a Pd-coated cantilever using an evanescent microwave probe. This stress was in the range of 5.26 - 8.59 X 107 Pa for H2 concentrations of 0.5 - 1.4% at room temperature, which is about three times larger than that found in the bulk palladium for the same range of H2 concentrations.
Enhanced pressure and temperature sensitivity of a fiber Bragg grating with polymer packaging
Author(s):
Yunqi Liu;
Zhuanyun Guo;
Xiaoyi Dong;
Zhiguo Liu;
Donghui Zhao;
Chunfeng Ge
Show Abstract
We demonstrate the higher pressure and temperature sensitivity of a fiber Bragg grating (FBG) sensor when it is packaged with a polymer jacket. The Bragg wavelength shift due to pressure and temperature can be enhanced by the polymer packaged by about 31.5 times for pressure and 7.7 times for temperature. The experiment results are consistent with the theoretical analysis. The sensitivity enhancement is due to the driving effect of the polymer substance. The 'structured' grating exhibits no significant chirp.
Fabrication of composite sol-gel optical channel waveguides by laser writing lithography
Author(s):
Wenxiu Que;
Yan Zhou;
Yee Loy Lam;
Yuen Chuen Chan;
Yuwen Chen;
Seng Lee Ng;
ChinYi Liaw;
Chan Hin Kam
Show Abstract
We report the preparation of high optical quality sol-gel waveguide films made from high titanium content organically modified silane (ORMOSIL) and the fabrication of optical channel waveguides in the deposited sol-gel films. The waveguide films were deposited on a solid substrate (such as silicon) by spin-coating and low temperature baking, and the channel waveguides were fabricated using laser writing and reactive ion etching (RIE). The properties of the sol-gel waveguide films were characterized using atomic force microscopy (AFM), ellipsometry, and UV-visible spectroscopy (UV-VIS). AFM and ellipsometry results showed that a dense and porous-free waveguide film could be obtained at the heat treatment temperature of 100 degrees celsius. The influence of the RIE parameters including O2 content, rf power, and pressure on etching rate of the sol-gel waveguide films have been investigated. After a number of exploratory experiments, suitable etching parameters for the case of photoresist mask layer have been obtained.
Two-dimensional fiber laser Doppler velocimeter by integrated optical frequency shifter
Author(s):
Kazuo Hasegawa;
Satoru Kato;
Hiroshi Itoh
Show Abstract
We developed a novel fiber laser Doppler velocimeter (FLDV) using an integrated optical frequency shifter on LiNbO3 substrate. The FLDV system consists of a small probe-head (diameter of 17 mm and length of 60 mm) with two polarization maintaining fibers for projection and one single mode fiber for detection. The FLDV system can measure the line velocity of two-dimensional vectorial flow by only one probe tilted against the direction of the flow. We will describe the construction of the measurement system and the measurements of actual velocities. Two vectorial components of the line velocity were obtained from the calculations between the interference signals detected on a photo-detector.
Application of an antiferroelectric liquid crystal cell as a self-aligning phase modulator
Author(s):
Hirofumi Kadono;
Satoru Toyooka
Show Abstract
In this study, we have examined the possibility of using an anti-ferroelectric liquid-crystal (AFLC) as a high speed phase modulator. The AFLC has the major advantage that it has three stable states in contrast to the ferroelectric liquid-crystal which has only two states. This feature permits the application of AFLC as a fast phase modulator in the phase shifting interferometer. However, AFLC also modulates the intensity of transmitted light as well as its phase. Based on theoretical analysis, it was found that doping a dichroic dye to AFLC cell can suppress the intensity modulation. Moreover, such a dye-doped AFLC phase modulator can perform as a self- align phase modulator. Such a self-align phase modulator permits a practically advantageous alignment-free optical system, for instance, in phase contrast microscope, point diffraction interferometer etc. Preliminary experiments were performed to demonstrate the validity of the dye-doped AFLC cell. Finally, we also examine the application of the dye- doped AFLC phase modulator to phase shifting interferometer.
Shear force characteristics and piezoelectric tip-sample distance control for NSOM
Author(s):
Jun Hee Lee;
Hyongryol Oh;
Dae gab Gweon
Show Abstract
The shear force characteristics of NSOM (Near field scanning optical microscopy) probe is examined. The NSOM probe is modeled as a 2'nd order mass-spring-damper system driven by a harmonic force. The primary cause of the decrease in vibration amplitude is due to the damping force -- shear force -- between the surface and the probe. Using the model, damping constant and resonance frequency of the probe is calculated as a function of probe-sample distance. Detecting the amplitude and phase shift of the NSOM probe attached to the high Q- factor piezoelectric tuning fork, we can control the position of the NSOM probe about 0 to 50 nm above the sample. The feedback signal to regulate the probe-sample distance can be used independently for surface topography imaging. Three- dimensional view of the shear force image of a testing sample with the period of 1 micrometer will be shown.
Novel nonoptical method of tip-sample distance regulation based on shear force in scanning near-field optical microscopy
Author(s):
Xiumei Liu;
Jia Wang;
Dacheng Li
Show Abstract
In this paper a novel method for tip-sample distance regulation based on shear-force is presented. A semicircular piezo-electric ceramic plate is used as the excitation as well as detection element, the electrode of which is divided into three segments. The first segment is excited by a generator and the second one is used to fix the fiber tip. The induced voltage on the third segment is used to detect the tip-sample distance. The approach curves show that it is very sensitive and the tip-sample distance can be regulated below 5 nm. Experimental results indicate that when the sample is covered with liquid the approach curve is different from that in the air. In addition, during experiments we found that at some resonant frequency the approach curve is different from the conventional shape. The phenomenon, if proved reliable, can be used to realize automatic and rapid tip-sample approach as well as small-scale distance regulation.
Determination of geometric properties of SNOM tips by means of combined far-field and near-field evaluation
Author(s):
Soenke Seebacher;
Wolfgang Osten;
Werner P. O. Jueptner;
Vadim P. Veiko;
Nikolay B. Voznesensky
Show Abstract
Scanning near field optical microscopes provide access to a variety of interesting material properties with a resolution in the nanometric size of scale. However, the quality of the optical fiber tip is of decisive importance. Because the production process of pulled and coated glass fiber tips is still highly empirical and full of defects, a technique would be useful to determine the tips' quality before they are shipped to the user or mounted in the microscope. This contribution shows an easy and fast full field method for the characterization of common 633 nm glass fiber SNOM tips. Size and shape as well as disturbances at the aperture can be recognized by means of evaluating the far field distribution of the emitted intensity and phase which are recorded by a CCD target. A numerical model is introduced which solves the reverse task that allows to draw conclusions from the measured intensity and phase distributions to the shape of the tip itself. Experimental investigation in a simple and robust setup and comparisons with combined near/far-field calculations show the working principle of this measurement technique for the analysis of SNOM tips.
Direct measurement of evanescent-wave interference patterns with laser-trapped dielectric and metallic particles
Author(s):
Min Gu;
Pu Chun Ke
Show Abstract
Interference patterns of evanescent waves have been recorded with laser-trapped dielectric and metallic particles. It has been demonstrated that the image contrast can be improved with laser-trapped metallic particles. Compared with other methods such as scanning tunnelling optical microscopy and shear-force optical microscopy, imaging with a laser-trapped particle is a simpler approach as no distance control is required. On the other hand, the pseudo effect introduced by the distance between a near-field probe and a sample may be reduced as a particle is trapped on the surface of a sample.
Enhancement of AFM images by compensating the hysteresis and creep effect within PZT
Author(s):
Hewon Jung;
Jongyoup Shim;
Dae gab Gweon
Show Abstract
In equi-force mode among the AFM scanning modes, the scanning data of a sample is acquired by Z-axis PZT input voltages. But, PZT actuator has a hysteresis and creep between the input voltages and the output displacements. These nonlinearities make a distortion in scanning images. We propose that the creep effect of stack-type PZT shows hysteresis property and classical preisach model can be applied to AFM scanning data according to this property. Finally we will prove that AFM image is improved by the classical preisach model application.
Radiation force exerted on subwavelenth particles near a nanoaperture
Author(s):
Kenji Okamoto;
Satoshi Kawata
Show Abstract
We investigate the possibility of optical trapping by evanescent photons localized near a subwavelength aperture. The radiation force exerted on a dielectric sphere near the aperture is numerically analyzed, and the result shows that the force on the sphere is attractive to the aperture. It is also found that the magnitude of the radiation force is larger than those of two other forces, the gravity and the force due to thermal fluctuation in water.
Scanning near-field optical microscope with a superfluorescent source
Author(s):
Guoping Zhang;
Hai Ming;
Jiangping Xie
Show Abstract
A superfluorescent source used for scanning near-field optical microscope (SNOM) has been developed in this paper. The superfluorescent source originates from an amplified spontaneous emission (ASE) produced by an Er-doped fiber, with a relatively wide spectrum from 1531 nm to 1537 nm. This kind of superfluorescent fiber probe has relatively high photon flux over an ordinary probe. Different image qualities are obtained by the SNOM system with the superfluorescent source and the laser source respectively. Experimental result shows that the coherent noise of the SNOM image is dramatically reduced with the superfluorescent source.
Nanoscale fabrication by interferometric lithography
Author(s):
Saleem H. Zaidi;
Steven R. J. Brueck
Show Abstract
Interferometric lithography (IL) techniques provide a demonstrated, low-cost, large area nanoscale patterning capability with feature resolution to approximately 50 nm. Combining IL with anisotropic etching (both by reactive-ion etching and by KOH wet etching) and with 3-D oxidation techniques provides a suite of techniques that accesses a broad range of Si nanostructures (as small as 10 nm) over large areas and with good uniformity. Optical characterization includes measurements of reflectivity for a wide range of 1D grating profiles, and Raman scattering characterization of Si nanostructures. Three regimes are found for the Raman scattering: bulk (to linewidths of approximately 200 nm), resonant enhanced (approximately 50 nm linewidths) and asymmetry and splitting (linewidths less than 20 nm).
Development of state-of-the-art devices on the subnanometer grinding machine tool for optical glasses
Author(s):
Hiroshi Eda;
Lotfi Chouanine;
Jun Shimizu;
Libo Zhou
Show Abstract
This paper gives an overview of development of the kernel technologies and parameter generalization at ductile mode conditions for grinding of optical glasses. An ultra precision machine tool capable of multiply functioning grinding, cutting, lapping or polishing has been newly developed for the ductile-mode grinding of hard-brittle materials. The key components built in the system are inclusive of the force transducer for sub-mN measurement and the PZT actuator for precise positioning. Through the grinding tests and scratching tests, the machining parameters governing the brittle-to- ductile transition have been established for a series of glasses. It also reveals a fact that the critical depth in grinding is thereabouts six times bigger than the critical depth in indentation and seven times than in scratching.
Fine OPC approach with gray-tone coding mask
Author(s):
Jinglei Du;
Jingqin Su;
Qizhong Huang;
Yixiao Zhang;
Yongkang Guo;
Chunlei Du;
Zheng Cui
Show Abstract
In this paper, a new method has been proposed to realize fine OPC with gray-tone coding mask instead of gray-tone mask. The relationships of the gray-tone coding mask and gray-tone mask have been discussed, and OPC simulation results are given with the gray-tone coding mask.
Temperature measurement with industrial color camera devices
Author(s):
Dieter J. Schmidradler;
Thomas Berndorfer;
Walter van Dyck;
Juergen Pretschuh
Show Abstract
This paper discusses color camera based temperature measurement. Usually, visual imaging and infrared image sensing are treated as two separate disciplines. We will show, that a well selected color camera device might be a cheaper, more robust and more sophisticated solution for optical temperature measurement in several cases. Herein, only implementation fragments and important restrictions for the sensing element will be discussed. Our aim is to draw the readers attention to the use of visual image sensors for measuring thermal radiation and temperature and to give reasons for the need of improved technologies for infrared camera devices. With AVL-List, our partner of industry, we successfully used the proposed sensor to perform temperature measurement for flames inside the combustion chamber of diesel engines which finally led to the presented insights.
Measurement of temperature on Scindapsus leaves subjected to ultraviolet radiation using infrared thermography techniques
Author(s):
Eisaku Umezaki;
Tomohiro Shimada
Show Abstract
The temperatures on the surfaces of intact Scindapsus (pothos lime) leaves subjected to ultraviolet radiation (UV-A, UV-B) as a function of time were investigated. The thermal images of leaves were taken at intervals of 1 min for 2 to approximately 11 h using a thermal video system, by which thermal information in the 3 to 5.4 micrometer infrared band were recorded. After the tests, the difference between the mean temperature of the leaf and the atmospheric temperature at each time point under each condition was determined. The results showed that the temperature differences for UV-A and UV-B irradiation were different from those for visible light supplied by a green house lamp. Therefore, the temperature on the leaf surface suggested the possibility of applications in the prediction of the level of UV-A and UV-B radiation.
Nondestructive evaluation of surface defects by the use of photothermal electrochemical imaging
Author(s):
Tsutomu Hoshimiya;
Ken-ya Ishikawa
Show Abstract
A new photothermal detection scheme based on a current-change in photothermally-enhanced electrochemical reaction is proposed and demonstrated. Nondestructive imaging of surface defects fabricated on a metal plate, immersed in an electrolyte, has been performed with a focused laser beam and detection apparatus of photoacoustic microscope (PAM). An imaging under the environment of electrolyte based on the principle of the detection was carried out with two- and tree terminal configurations, these results were compared with that obtained with conventional photoacoustic (PA) imaging.
Dispersion properties and data analysis of meromorphic nonlinear susceptibility of layered two-phase nanocomposites
Author(s):
Erik Mikael Vartiainen;
Kai-Erik Peiponen;
Toshimitsu Asakura
Show Abstract
The case of layered two-phase nanocomposites has been numerically studied. Contrary to the earlier studies on the subject, material's susceptibilities are allowed to be complex valued and to change as a function of frequency. Thereby, new effects arise, e.g., the phase of the effective third-order susceptibility (chi) eff(3) of a nanocomposite can have a huge frequency dependent increase near resonances compared to corresponding phase changes of (chi) (3) of the constituent materials. Unfortunately, the phase changes cannot be predicted from the amplitude measurement (chi) eff(3) by the Kramers-Kronig methods, because (chi) eff(3) is, in general, a meromorphic function in a complex frequency plane, and thus, conventional Kramers- Kronig relation does not exist between the amplitude and phase of (chi) eff(3). In this paper another type of phase retrieval procedure, based on the maximum entropy model, is shown to be applicable for (chi) eff(3).
Optical control of the pitch in cholesteric liquid crystals
Author(s):
Koichiro Shirota;
Kaori Tachibana;
Ichirou Yamaguchi
Show Abstract
It has been shown that optical control of a spiral pitch in cholesteric liquid crystals (CLCs) by laser light irradiation is possible. Because of the spiral periodic structure, the CLCs shows unique optical characteristics with various polarization dependence. Then, the CLCs have a potential for application to polarization selective device whose properties can be changed by light irradiation. The CLC used was a mixture of cholesteryl chloride and cholesteryl pelagonate, and a mixing ratio selected for the wavelength of a probe laser was CC:CP equals 33.6:66.4. To control the pitch, CLCs was doped with azobenzene at a concentration of 5 mol%. Optical isomerization of the dye molecules induced a change of the pitch, and hence the selective reflection band is shifted. Irradiation by a He-Cd and an Ar+ laser shifted the selective reflection band of sample to shorter and longer wavelength, respectively. Hereby the spiral pitch in CLC was reversibly changed by 10 nm.
Optically induced self-growing of fiber structure in a photopolymerizable resin
Author(s):
Satoru Shoji;
Satoshi Kawata
Show Abstract
We present evidence of optically-induced growth of fiber patterns into a photopolymerizable resin. Optical growth of a single or multiple fibers is achieved by focusing a laser light into the photopolymerizable resin used. The fiber growth is due to an effect in which photopolymerization of the resin upon light irradiation produces an increase of the resin refractive index, the change of which, in turn, confines the light propagation into waveguide-type fiber structures. We have also observed that two optically grown independent fibers can merge to form a single fiber under specific conditions. We have studied the dependence of this optical growth of fiber structures phenomena on all the experimental parameters, including the numerical aperture (N.A.) of the lens used to focus the light, the light power, and the exposure time.
Laser-diode-tuned chromium atom trapping and fabrication with atom optics technology
Author(s):
Kenji Okamoto;
Hironobu Inouye;
Yasushi Inouye;
Satoshi Kawata
Show Abstract
We developed a laser-beam-controlled atom-manipulation system to deposit nanometric structure of atoms on a substrate. Atom beam of chromium is thermally evaporated and collimated with Doppler cooling technique using frequency-tuned laser diode. The gradient force is exerted on atoms by a standing wave over the substrate, and atoms are trapped in a low potential region of the standing wave. Consequently, a series of lines are formed on the substrate with the same periodicity to the standing wave. We present the analysis of trajectories of atoms in the light force potential to find conditions of the laser power, the sign and the degree of the detuning of the laser frequency from the resonance frequency of the atom, to reduce the width of the structure.
Photorefractive effect in an inorganic nanoparticle polymer-doped system
Author(s):
Yanqiang Yang;
Jimin Huang;
Qiuju Wu;
Guijuan Sun;
Haosheng Fei;
Zhenqian Wei;
Jiachong Shen
Show Abstract
In this paper, photorefractive (PR) effect of polymer doped inorganic nanoparticles is reported. In the photorefractive polymer material system, Cu2S nanoparticles were used as photo-sensitizer, N-polyvinylcarbazole (PVK) was used as carrier transport agent, and EPNAC molecules were used as electro-optical molecules. Two beam coupling in this kind of composite was studied. The experimental results prove that this kind of inorganic nanoparticles can be used as photosensitizer in polymer PR materials.
New deep-UV microscope
Author(s):
Naoya Eguchi;
Michio Oka;
Yutaka Imai;
Masaki Saito;
Shigeo R. Kubota
Show Abstract
We report a deep-UV microscope having the best resolution of any optical microscope. The resolution limit is less than 0.1 micron, which is close to the resolution limit of a scanning electron microscope (SEM). Moreover, measurement without vacuum chamber is possible using the new deep-UV microscope. The deep-UV microscope is suitable for inspecting semiconductors, magnetic heads and optical disks.
Microscope for measurement of discontinuous deep microstructure topography
Author(s):
Mingbao Zhou
Show Abstract
The paper describes the new microscope for accurately measuring the three-dimensional surface topography of deep and discontinuous microstructures, which is based on two- wavelength phase-shifting interferometry (PSI) and data analysis. The microscope mainly consists of dual-path interference microscopic optical system, CCD image sampling system, control system and data analysis/processing. The related techniques include five-step PSI technique, the generalized two-wavelength interferometry (TWI) and a new data analysis/processing technique. The depth resolution of the microscope is 0.5 nm, the depth measuring accuracy is better than 1.3 nm. When the 20X microscope objective (NA equals 0.4) is used, the spatial resolution of the microscope is about 0.5 micrometer, the field is about (phi) 1.325 mm.
Two-photon-induced photon oxidation as a means for 3D optical data storage
Author(s):
Andong Xia;
S. Wada;
Hideo Tashiro;
Wenhao Huang
Show Abstract
We present a new approach for multi-layered optical data storage in C60 doped polystyrene film. We find that photo- oxidation may increase the fluorescence intensity of C60 molecule by two-photon excitations in a wide wavelength region (780 - 910 nm) from a 100 fs Ti:sapphire laser. The proposed scheme encodes the digital bits by photo-oxidation of C60 induced by two-photon excitation, and reads the increase fluorescence from the oxidation area. The high fluorescence signal can be easily distinguished as bit 1, and low fluorescence signal, as bit 0. This change in the fluorescence intensity could be used to encode information for read-only- memory.
High-intensity nanosecond white-light source using a commercially available Xe arc lamp
Author(s):
Shin Itami;
Tsutomu Araki
Show Abstract
We have developed an intense, white emission spectrum, nanosecond pulsed light source using a commercially available Xe short-arc lamp. This light source is simple in construction, physically compact and easy to operate. In the previous study, we have applied 35 - 75 W type lamp as the light source. In the present study we applied two 150 W type Xe-arc lamps. Because the electrode gap of the 150 W lamp is wider than that of 35 - 75 W type, applied voltage higher than 16 kV is required for the pulsed operation of the 150 W lamp. Intense light pulses as large as 140 W (peak power) of 15.2 ns duration (FWHM) were obtained repetitively from the Xe lamps. This lamp produced broadband emission spectrum (250 - 650 nm) according to discharge of Xe gas. Present lamp operation is free-running type, but it is possible to control the discharge timing using a thyratron. The intense emission characteristic can be utilized not only as the excitation light source in time-resolved fluorometry but also as the stroboscopic illumination source in high-speed photograph.
Mode regulation of a laser resonator by a micro-optic mirror
Author(s):
Guoping Zhang;
Xianhe Zhang;
Sitao Li;
Jiaxiong Ye
Show Abstract
A novel method for mode regulation of a laser resonator is presented this paper. The traditional spherical mirrors of the laser resonator are substituted by the micro-optic mirrors, which are produced by the binary optical technology. The phase distributions of the micro-optic mirrors may be designed carefully so that the output mode of the laser resonator is regulated as an arbitrary desired field distribution. Several mode fields, such as a fundamental-mode Gaussian distribution and a circular or rectangular uniform intensity distribution, are analyzed in our discussion.
New type of laser stripe generator
Author(s):
Youna Lin;
Jinghai Liu
Show Abstract
A new type of laser stripe generator has been developed, which has the characteristic of beam tunability in its width and depth. It is composed of light source and cylindrical optical system. Also, the property and function of each component are introduced. The paper provides an Applied Case of laser stripe generator.
Ultraprecision machining of ceramics for optical components
Author(s):
Hiroshi Eda;
Jun Shimizu;
Libo Zhou
Show Abstract
A machining system was developed, to achieve ductile-regime machining of ceramics and glasses for optical components. The machine tool is capable of cutting, grinding, lapping or polishing hard and brittle materials in ductile-regime. As a key component in building the system, giant magnetostrictive alloys with large output power and outstanding elongation are employed to comprise an ultra-precision actuator. The actuator can be used as a high frequency vibration actuator as well as a fine positioning device. The actuator was made of newly developed composition material. In this paper, the results of the actuator used as a high-accuracy positioning device in grinding processes are presented. Various kinds of ceramic materials for optical components were subjected to experiments. The results indicate that the newly developed machine tool is capable of realizing ductile-regime process.
Continuous-phase diffractive optical element to realize uniform target illumination in inertial confinement fusion (ICF)
Author(s):
Qiaofeng Tan;
Yingbai Yan;
Guofan Jin;
Minxian Wu
Show Abstract
Rigorous requirements of target illumination are requested in Inertial Confinement Fusion (ICF) experiments, such as flat top, steep edge, low sidelobes and high light efficiency. Using Diffractive Optical Elements (DOEs) to realize such uniform illumination has many advantages, such as high light efficiency of pure phase modulation, strong flexibility of phase design and so on. A kind of hybrid algorithm based on hill-climbing and simulated annealing is utilized for phase design because of the ability of strong convergence of the hill-climbing and the global optimization potential of the simulated annealing. Continuous phase should be adopted to increase the light efficiency and decrease wide-angle scattering. The continuous phase DOEs with diameter 100 mm has been obtained by gray-level mask and ion-etching on the K9- glass substrate. The DOEs' interferogram and local profiles are given to detect the precision of manufacturing. The intensity distribution of the focal spot are measured by a general CCD, and a series of attenuators are used to increase the dynamic range of the CCD. The results after data- processing show that the uniform illumination has been obtained.
Microlens fibers fabricated by a melting-tapering process using a CO2 laser
Author(s):
Abdelrafik Malki;
Frederic Van Lauwe;
Renaud Bachelot;
Olivier Latry;
Mohamed Ketata;
Pascal Royer
Show Abstract
Hemispherical microlenses have been fabricated at the end of a single-mode optical fiber by a new two-steps method which uses only a continuous CO2 laser. In the first step, the fiber is heated by the laser and stretched until its split resulting in two symmetrical tapers. In the second step, we form the microlenses by laser melting the taper ends. Parameters of heating and stretching are automated and optimized to ensure the reproducibility. The microlens characterization, including the focal length and beam waist measurements, has been performed. It shows the interest of the microlens-fiber to several applications.
Binary deposition method using standard CMOS structural layers to fabricate optical gratings and microlenses
Author(s):
Lung Jieh Yang;
P. C. Liu;
Shung-Wen Kang;
W. C. Du
Show Abstract
The binary lithography combined with precise control of RIE (Reactive Ion Etch) could fabricate the 8-level blazed gratings with the reflective efficiency above 80% in recent years. The pixel size of the 8-level grating is often designed to be 32 microns or even larger due to the manipulation error of the mask-aligner. By the excellent augmentation of the mask-stepper, which is popular in IC industry, the smaller pixel size or the higher-order levels of the gratings could be achieved ideally. Unfortunately, we hardly used the mask- stepper to meet the precision requirement for the excuse of process or material incompatibilities in standard IC process. Herein, we used a 'binary deposition method' as the counterpart of the current binary optics or binary etching method. By the standard CMOS process, all the designers have to do is to edit the layouts of multiple accumulated layers of poly-silicon and metal with a micrometer variation between each two planar layers. A classical demonstration for the 8- level gratings by the standard CMOS layers was depicted in this paper. Therefore, the sub-micron precision of the lithographic stepper is now practically available. Moreover, it even needs no post processing after the CMOS fabrication. A grating layout by the binary deposition method is under the foundry service provided by Chip Implementation Center (CIC), National Science Council, Taiwan, Republic of China. By the appropriate layout design, other reflective optical lenses have chances to be done as well as the blazed gratings similarly.
Next-generation fabrication technologies for optical pickup devices in high-density optical disk storage systems
Author(s):
Shigeru Hosoe
Show Abstract
This paper shows a direction of friction technologies to make aspherical plastic objective lens with higher optical performance for high density optical disk storage systems. Specifically, a low birefringence and low water absorption (less than 0.1%) optical resin, low tool abrasion mold material, high circularity diamond tool which nose circularity is less than 30 nm, and 1 nm axis resolution precision lathe which tool position is stabilized against drift by environmental change are referred. Cut optical surface of a mold sample was constantly attained in less than 5 nmRtm surface roughness. Using these new technologies, aspherical plastic objective lens (NA0.6) for DVD which wave aberration is less than 35 m (lambda) rms was realized.
Attenuated phase-shifting mask and its encoding method
Author(s):
Chongxi Zhou;
Feng Boru;
Desheng Hou;
Jin Zhang
Show Abstract
Attenuated phase shifting mask and that with optical proximity correction is adopted to improve resolution of photolithography based on some calculation results. The first factor k1 of the photolithography could be to 0.50, and the optimal transmission is about to 8 to approximately 10%. And a new kind of method of making attenuated phase shifting mask by encoding is put forward, and the theoretical calculation results are accordant to the conventional attenuated shifting mask.
Spectroscopic study on second-harmonic generation from a reconstructed silicon surface
Author(s):
Jun Chen;
Dehuan Huang
Show Abstract
The pump wavelength dependence of the optical second harmonic generation from Si(100)-2x1 has been investigated by use of a tunable Ti:Sapphire laser. Significant enhancement of second harmonic signal around pump wavelength of 850 nm was observed. Such an enhancement is considered be caused by resonance related to Si surface dangling-bond states.
Implementing an integrated infrared spectrometer: a theoretical study
Author(s):
Daniel Puiu Poenar
Show Abstract
This paper explores the basic notions and limitations which should be considered in the design of an integrated spectrometer implemented using microelectronic processing. The infrared (IR) range is the main focus of attention, but the design rules are meant to be very general and more wavelength domains will have to be taken into consideration. Some general principles and design rules necessary to generate the desired spectral dispersion of a certain wavelength range will be presented, by means of which an integrated spectrometer could be designed/optimized.
Rewritable broadband filters for color image analysis
Author(s):
Kanae Miyazawa;
Markku Hauta-Kasari;
Satoru Toyooka
Show Abstract
In this study, we propose an optical transparent broad-band filter system which can be used to measure a color spectrum and two-dimensional spectral images. The filter function of this system can be changed and rewritten arbitrarily. Spectral distribution of an object color can be represented by a set of inner products between optimized filter functions and the spectral distribution of a sample. In our system, a test image is observed through the filter part consists of a liquid crystal spatial light modulator (LCSLM) and a linear variable filter (LVF) attached together. The intensity image of a sample is taken while the joint device (LCSLM and LVF) is moving just in front of the lens aperture of the CCD-camera. The spectral distribution of the intensity image through the proposed filter almost coincided with the expected filter functions. From the detected intensity images correspond to the inner products between the color filters and a sample, the color spectra of the sample were reconstructed by the use of inverse matrix. The data obtained from the filtering process is only four monochrome images. It is convenient for storing and transmitting the spectral image. The experimental results of measuring a color spectrum and two-dimensional spectral images are presented.
Resistive YBaCuO microbolometers for infrared imaging applications
Author(s):
Linh Phong Ngo;
S. N. Qiu;
Bruno Tremblay
Show Abstract
Details of the fabrication process and figures of merit of resistive YBaCuO micro bolometers are reported. Thin films of YBaCuO were prepared on Si wafers under conditions that promote formation of the semi-conducting phase at room temperatures. Effects of the preparation conditions on activation energy of YBaCuO were studied to obtain films with a large temperature coefficient of resistance (TCR). TCR with values of up to 0.04 K-1 was achieved uniformly on 10- cm wide wafer areas. Bulk micromachining was used to create 60 X 60 micrometer2 bolometers on Si3N4 bridges with a thermal conductance of approximately 7.6 X 10-7 W/K. The low frequency responsivity and detectivity of the micro bolometers were respectively approximately 7 X 104 V/W and 3 X 109 cm.Hz1/2/W at room temperatures. These figures compare favorably with figures of other classes of un-cooled micro bolometer and are consistent with those derived from thermal properties of the bridge. Under normal operating conditions and assuming f/1.0 optics, the NETD of focal planes that make use of these micro bolometers was estimated to be less than 50 mK in the spectral range of 8 to 14 micrometer.
Graphic-oriented environmental monitoring system
Author(s):
Zesheng Zhu;
Ling Sun
Show Abstract
This paper considers a graphic-oriented environmental monitoring system. The paper objective is to find an effective graphic-oriented method for designing and implementing this advanced environmental monitoring system. The key issues addressed in the study include the system design and implementation principle, the approach adopted in our current work, and the system construction techniques.
Electromagnetic waveband in environmental monitoring
Author(s):
Fengjie Yang;
Han Zhen;
Liqing Lei;
Cailan Gong;
Xiaoning Song
Show Abstract
The destruction of the environment caused by the pollution of the environment certainly leads to the change of the radiant specific property of the electromagnetic wave of surface features. This alteration concretely expresses in the spectrum variation of water, soil and vegetation. This article, combining with the spectrum test of the mine, analyses and discusses the different categories of surface features, the spectrum variation caused by pollution and the optimum wave band applied to the environmental monitoring of the mine. And give proposals for the selection of the wave band of the sensor and designs.
Antireflection structures for visible and infrared wavelengths fabricated on silicon substrates by fast atom beam etching
Author(s):
Yoshiaki Kanamori;
Minoru Sasaki;
Kazuhiro Hane
Show Abstract
Subwavelength structured (SWS) surface directly patterned on a substrate performs as antireflection surface. We fabricated the two-dimensional SWS surfaces on crystal silicon substrates and tested the reflection properties for visible and infrared wavelengths. The SWS surfaces were patterned by electron beam lithography and etched by SF6 fast atom beam (FAB). In this work, the FAB process was first applied to fabricate the SWS surface. We fabricated the hole type SWS surface and the column type SWS surface. In both types, the grating period was 200 nm and the grooves were approximately 275 nm deep. The dependence of the reflectivity on the free-space wavelength between 200 nm and 2500 nm was examined. In addition, dependence of the reflectivity on the incident angle was examined with He-Ne laser light. From those experimental results, it was shown that the fabricated SWS surfaces, especially column type SWS surface, prevented the reflection in the wide ranges of wavelength (200 nm less than (lambda) 0 less than 2500 nm) and incident angle (5 degrees less than (theta) less than 60 degrees).
Ladar fiber optical liquid level sensor system
Author(s):
Wei Peng;
Junxiu Lin
Show Abstract
A novel fiber-optic liquid level sensor of Laser radar is reported in this paper. Using the absolute technique of Ladar in which the phase of amplitude modulated lightwave reflected from the liquid face is compared with that of the original modulate signal, the liquid level can be measured precisely. A special symmetric compensating optical system, which has a common axis for light emitting and receiving, is proposed to eliminate many adverse effects. Separating and connecting its electric part and optical part by optical fiber cable, the one-time electronic-free optical measurement has been realized on a simulated oil tank and an accuracy of plus or minus 0.3% is achieved within a temperature range of 20 degrees to approximately 40 degrees Celsius over a measuring range of 0 to approximately 6 m.
High-sensitivity long-period fiber grating temperature sensor based on intensity measurement
Author(s):
Yunqi Liu;
Chunfeng Ge;
Donghui Zhao;
Zhiguo Liu;
Zhuanyun Guo;
Xiaoyi Dong;
Hwa-Yaw Tam
Show Abstract
We design a kind of all-fiber high-sensitivity temperature sensor based on intensity measurement, by using long period fiber grating (LPG) as sensor element and using tunable erbium-doped fiber ring laser as optical source. In the temperature range of 74 degrees Celsius, the logarithm of the transmissive intensity of LPG is linear with the measured temperature and the linearity of sensing measurement can be repeated well. The resolution of temperature measurement is 0.1 degrees Celsius.
Optical fiber Bragg grating accelerometer
Author(s):
Stephanus J. Spammer;
Peter L. Fuhr;
Yinian Zhu;
Anatoli A. Chtcherbakov
Show Abstract
A cantilever beam and fiber Bragg grating is used to measure acceleration. The cantilever induces strain on the grating resulting in a Bragg wavelength modification which is subsequently detected. The output signal is insensitive to temperature variations and for a temperature change from -20 degrees Celsius to 40 degrees Celsius, the output signal fluctuated less than 5% without any temperature compensation schemes. Because the sensor does not utilize expensive and complex demodulation techniques it is potentially inexpensive. For the experimental system a linear output range of 8 g could be detected.
MJ internal thread used for aerospace and its noncontact test method with a fiber optic sensor
Author(s):
Yong Zhao;
Pengsheng Li;
Zhaobang Pu
Show Abstract
The characteristics of MJ internal threads used for aerospace products are introduced in this paper. The mathematical models and the design of a novel fiber-optic sensor for non-contact quantification test on MJ internal threads are presented. As to the feasibility of the sensor head, the theoretical analysis is given, and the experimental results agreed with them. The resolution the sensor developed can reach 0.1 micrometer when used to measure reference planes. And for the MJ internal thread measurement, the estimated uncertainty was around plus or minus 25 micrometer.
Optical dc current and voltage measurement by superposing ac magnetic or electric field
Author(s):
Masaru Higaki;
Kunio Fujii;
Shizuo Yamaguchi
Show Abstract
Optical DC current and voltage measurement using Faraday or Pockels effect necessitates the compensation of light intensity variation with some methods, because it is possible the intensity variation may give rise to a measuring error. We have proposed a method which suggests superposing AC magnetic field on linearly polarized light or AC electric field on elliptically polarized light and compensating light intensity variation by detecting AC components caused by constant AC magnetic or electric field. Experiments of long term stability for DC current and voltage measurement were carried out by using flint glass for DC current measurement and B12SiO20 (BSO) crystals for DC voltage measurement. An experimental result of DC current measurement where DC current of 1.0 A was passed under AC current of 1 kHz 1.5 Arms showed that the modulation depth without compensation through AC magnetic field varied largely with time because of the temperature rise of the flint glass, but that with compensation through AC magnetic field hardly varied with time and the effectiveness of AC magnetic field superposition was confirmed. The same compensation method was applied to optical DC voltage measurement using Pockels effect. An experimental result of DC voltage measurement where DC voltage of 500 V was applied under AC voltage of 5 kHz 50 Vrms clarified that the time variation of the modulation depth with compensation through AC electric field was small compared with that without compensation through AC electric field.
Comparison of sensitivity of optical waveguide chemical sensors between TM and TE modes
Author(s):
DeKui Qing;
Ichirou Yamaguchi
Show Abstract
To investigate the dependence of the sensitivity of optical waveguide sensors on the polarization of guided modes, we have analyzed their absorption coefficients for both TE and TM modes by group index method [D.-K. Qing, X-. M. Chen, K. Itoh, M. Murabayashi: J. Lightwave Technol. 14, pp. 1907-1917, 1996]. As field distributions of TE and TM modes are different, the absorption coefficient for TE and TM modes are different. For open clad type evanescent wave sensors, whose mode is more favorable depends on whether the refractive index of the measurand is lower or higher than that of the substrate; for buffered clad type evanescent wave sensors, This depends on the role of the buffer layer; for sensing layer type evanescent wave sensors, TE mode has larger sensitivity than TM mode; for guided wave sensors, both TE and TM mode are suitable for highly sensitive sensors.
Integrated optic pressure sensor using intermodal interference between TM-like and TE-like modes
Author(s):
Kazuhiko Hasebe;
Masashi Ohkawa;
Chikara Nishiwaki;
Seishi Sekine;
Takashi Sato
Show Abstract
An integrated optic pressure sensor based on intermodal interferometry is described. The sensor consists of a straight waveguide supporting the lowest-order TM-like and TE-like modes and a rectangular diaphragm as a pressure sensitive region. The waveguide is placed along an edge of the diaphragm to maximize the sensitivity of the sensor. The output intensity of the sensor system is dependent on a difference of phase retardations induced in the two guided modes by the applied pressure via the photoelastic effect. The sensor was fabricated using two glass substrates: a Corning 0211 glass with a thickness of 300 micrometer and a thick substrate with a 10 mm X 10 mm square hole to define the diaphragm. The two substrates, were finally bonded together by UV curing adhesion after the waveguide was formed on the thin substrate. The fabricated sensor was tested using a He-Ne laser at 633 nm. We successfully obtained the sinusoidal change of the output power versus the applied pressure. The halfwave pressure was evaluated to be about 80 kPa experimentally.
Synthetic double-exposure method for security holograms: image estimation based on numerical simulation
Author(s):
Nobukazu Yoshikawa;
Masahide Itoh;
Toyohiko Yatagai
Show Abstract
We have developed a synthetic double exposure (SDE) method of the computer-generated holograms (CGHs) for security applications. This method is based on incoherent multiplexing of two types of coding methods on binary CGHs: a cell-oriented and a point-oriented. The CGH synthesized by the SDE can have multiple image planes from the image region to the Fraunhofer region. In fabrication process of the SDE, the point-oriented CGH, that is, the image-type hologram is erased slightly by the cell-oriented CGH. We estimate here the image quality and the diffraction efficiency of the reconstructed image in the image-type hologram by the SDE using numerical simulations. In our simulations, the cell-oriented CGH occupied only 14% of the entire hologram area. The diffraction efficiency of the image-type hologram by the SDE was about 80%. Therefore, the information of the image-hologram was preserved sufficiently. The CGH including image-, Fresnel- and Fourier-type holograms was fabricated using the direct writing of electron-beam resist in electron-beam lithography. These reconstructed images were almost identical to the desired ones.
Optical encryption system using a spatial light modulator
Author(s):
G. Unnikrishnan;
Joby Joseph;
Kehar Singh
Show Abstract
We implemented an optical encryption system that uses random Fourier plane encoding as the encryption method. In this method, data is encrypted by using a random phase function in the Fourier plane. In the earlier systems, the random phase function has been mostly implemented by fabricating random phase mask using photolithographic technique or by photographic bleaching process. We implement the binary random phase function using a Ferroelectric spatial light modulator (SLM). The use of SLM eliminates the need of fabricating the random phase mask which makes the SLMs suitable candidates in the encryption systems. The encrypted image which is a complex function is holographically recorded in a photorefractive BaTiO3 crystal.
Discrimination of portraits using a hybrid parallel joint transform correlator system
Author(s):
Rieko Inaba;
Asako Hashimoto;
Kashiko Kodate
Show Abstract
A hybrid parallel joint transform correlation system is demonstrated through the introduction of a five-channel binary zone plate array and is applied to the discrimination of portraits for a presumed criminal investigation. In order to improve performance, we adopt pe-processing of images with white area of 20%. Furthermore, we discuss the robustness.
Local plasmon sensor using a gold colloid monolayer
Author(s):
Takayuki Okamoto;
Tetsushi Kobayashi;
Ichirou Yamaguchi
Show Abstract
A new optical sensor using local plasmon resonance is proposed. The sensor uses the principle that the extinction efficiency of a small metal particle depends on the effective refractive index of the medium surrounding the particle. We use gold colloid monolayers for the sensor, in which colloidal gold particles of 16-nm diameter are immobilized on a glass slide using functional organic coupling agent. We measured absorption spectra of the gold colloid monolayers immersed in liquid samples and coated with film samples. In the experiments for poly-(methyl methacrylate acid) films we obtained the thickness sensitivities of 0.009 absorbance/nm and 4.3 nm/nm for peak absorbance and for resonance wavelength, respectively.
Three-dimensional optical recording with the ferroelectric domain reversal in a Ce-doped SBN:75 crystal: experiment and calculation
Author(s):
Masaki Hisaka;
Hidekazu Ishitobi;
Satoshi Kawata
Show Abstract
We have developed a bit-oriented three-dimensional domain memory with a photorefractive crystal. A Ce-doped SBN is used to record a bit data. The ferroelectric polarization is reversed by a focused laser beam in a crystal with the temperature at 38 degrees Celsius to form a bit data. The recorded domain is stable at 15 degrees Celsius. The data is read as the refractive index change induced by spontaneous polarization via Pockels effect. We show the domain image observed with phase contrast microscope. We also show the computer simulated images. The result in experiment is in good agreement with the simulated result.
Photofabrication of a photonic crystal using interference of a UV laser
Author(s):
Satoru Shoji;
Nicholas Smith;
Satoshi Kawata
Show Abstract
We have developed a method to fabricate photonic crystals using an interference pattern of laser beams. Photopolymerizable resin is used for solidifying a lattice. Interference of two beams forms a one-dimensional grid and a two-dimensional lattice, and that of three beams forms a three-dimensional hexagonal lattice. The experimental setup and the process of fabrication are described. The use of the structure to photonic crystal is also discussed.
Optical sensing of fractal aggregates of particles using backscattering enhancement
Author(s):
Katsuhiro Ishii;
Toshiaki Iwai
Show Abstract
To coherently backscattered light from a dense disordered medium generates an intensity peak in the far field due to the constructive interference in the time-reversal pairs of light. The spatial properties of the particle distribution in the suspension affect characteristics of the peak intensity distribution. In our report, the coherently backscattered light from particles aggregated in dense and absorbent colloidal suspensions is experimentally investigated with relation to the fractal dimension of media. The investigation is concerned with a decreasing slope in the intensity distribution. Dense colloidal suspensions of polystyrene latex spheres are used in the experiment and the aggregation of particles is induced by adding the NaCl solution to colloidal suspensions. As a result, the decreasing slope in intensity distribution changes suddenly at an amount of NaCl solution, which implies the fractal clusters form in the dense suspension. The quantitative estimations for the dimensions of media reveal that the dimension estimated from the copolarized intensity depends both on the distribution of clusters and on the spatial structure inside a cluster whereas the cross- polarized intensity depends only on the spatial structure inside a cluster. Furthermore, it is clearly shown that such a decreasing behavior is independent of absorption.
Analysis of the structure of the collective motion of small particles by dynamic light scattering
Author(s):
Masazumi Higuchi;
Hiroshi Takano;
Osamu Yamaguchi;
Masayuki Itoh
Show Abstract
A new optical sensor using local plasmon resonance is proposed. The sensor uses the principle that the extinction efficiency of a small metal particle depends on the effective refractive index of the medium surrounding the particle. We use gold colloid monolayers for the sensor, in which colloidal gold particles of 16-nm diameter are immobilized on a glass slide using functional organic coupling agent. We measured absorption spectra of the gold colloid monolayers immersed in liquid samples and coated with film samples. In the experiments for poly-(methyl methacrylate acid) films we obtained the thickness sensitivities of 0.009 absorbance/nm and 4.3 nm/nm for peak absorbance and for resonance wavelength, respectively.
Numerical analysis of enhanced backscattering from random fractal media
Author(s):
Jun Uozumi;
Takamitsu Saito
Show Abstract
Enhanced backscattering from random fractal media is investigated by means of Monte Carlo simulations based on a randomized Menger sponge model of the media. Dependence of the coherent peak on the fractal dimension D is obtained for 1.5 less than or equal to D less than or equal to 2.79, and it is found that the slope of the peak shoulder in a log-log plot increases with D until D equals 2.5 and then decreases for a further increase in D. This behavior is elucidated on the basis of probabilities of the scattering free path, the number of scattering in a multiple scattering path, and the separation of two end particles in a scattering path.
Fiber optic spectrophotometry for monitoring dissolved oxygen in a tropical ornamental fish tank environment
Author(s):
Anand Krishna Asundi;
Jun-Wei Chen;
Duo-Min He
Show Abstract
Using Fiber Optic Spectro-Photometry (FOSP) methodology, a set of high sensitivity fiber optic oxygen monitoring system performing NDT is developed for fish farming environment. The working principle of the sensor is based on the detection signal at a particular wavelength due to the fluorescence and quenching of coated dye (ruthenium complex) in response to oxygen concentration at the tip of the probe. This paper looks into the application of fiber optics oxygen sensor in an aquatic environment. A comparison study of the optical probe was made with a conventional electrochemical oxygen sensor. Both sensors were setup to monitor the dissolved oxygen of an aquatic system for a period of time. This new methodology offers an alternative choice for monitoring dissolved oxygen. Apart from the possibility to miniaturize the monitoring equipment for aquatic environment, it is also feasible to 'bundle' other chemical sensors together into one single cable, thus achieving compactness, effectiveness and yet without forgoing whatever the traditional electrochemical sensors could offer.
Nonlinear excess fraction method: a robust temporal phase-unwrapping algorithm
Author(s):
Yudong Hao;
Yang Zhao;
Dacheng Li
Show Abstract
Phase unwrapping, an unavoidable process in grating projection profilometry based on phase measurement, often manifests itself as the major obstacle that compromises measuring reliability and prevents automated profiling. In this paper, a robust temporal phase unwrapping algorithm, namely, non- linear excess fraction method (NLEFM) is proposed, which may enlarge the measuring range by dozens of times at no cost of accuracy. The algorithm presented in a general form demonstrates that the conventional linear excess fraction method can be readily extended into non-linear domain once certain condition is met. This novel method has been successfully applied to profiling complex objects with abrupt discontinuities and surface isolations. The multi-frequency grating projection profilometer based on NLEFM is promised to be developed into a robust, high accuracy and automated shape measurement system.
Amplitude measurement of a sinusoidally oscillating object using a frequency-ramped laser diode with some intensity modulation indices
Author(s):
Masaaki M. Imai;
Masashi Kondoh;
Naohiro Murakami
Show Abstract
An optical heterodyne interferometer with a frequency-ramped laser diode (LD) has been constructed for amplitude measurements of a sinusoidally oscillating object. In order to eliminate the effect of intensity modulation without complexity in optical setup, an optical interferometry operating under a small index of intensity modulation has been proposed and its effect on the amplitude measurements of an oscillating object has been analyzed based on spectral analysis of interference beat signal. From the simplified analysis for some ratios of beat frequency to modulation (ramped) frequency and for some intensity modulation indices, it is confirmed that the theoretical analysis and the experimental results are in relatively good agreement.
Observation of actual pitting corrosions by photoacoustic imaging
Author(s):
Yoichiro Hiwatashi;
Haruo Endoh;
Tsutomu Hoshimiya
Show Abstract
In this study, imaging of the actual pitting corrosions by photoacoustic microscope (PAM) has been demonstrated for the first time. Two types of the actual pitting corrosions are generated by immersion and electrochemical method. Immersion tests are conducted in sodium chloride aqueous solutions for pure aluminum plate. Electrochemical method are conducted by electrolysis under the continuous electrode with potentiostatt in sodium chloride aqueous solutions for pure aluminum plate. Nondestructive measurement of pitting corrosions was carried out with PAM and simultaneous measurement of amplitude and phase of the photoacoustic (PA) signal at every point of scanning is carried out, and the PA amplitude and phase images are obtained. The PA amplitude signal intensity changed with both shape and depth of a pitting corrosions. Phase signal intensity relatively reflected the depth and cross section of a pitting corrosion. Furthermore, comparing of the imaging of the actual pitting corrosions and the simulated pitting made by chemical etching.
Multifunctional photoacoustic microscope and its applications to NDE of surface and undersurface defects
Author(s):
Ken-ya Ishikawa;
Katsuhiko Miyamoto;
Tsutomu Hoshimiya
Show Abstract
A photoacoustic microscope (PAM) with a multi-function is designed and fabricated. Two scanning modes with galvanometric scanners and linear-motor stages, which present quite environment suitable for gas-microphone photoacoustics, are available in this microscope. Beam scanning, data acquisition, and signal processing is controlled by a graphical software LabView. Applications to the PAM to nondestructive evaluation of surface and undersurface defects of the solid specimens are also demonstrated.
3D sensing of a nonstationary surface
Author(s):
Sergei Vasilievich Mikhlyaev
Show Abstract
Problems of active coherent triangulation sensor applicability to non-stationary reflective 3D surface sensing are considered. As is shown in the paper, the accuracy of a sensor is connected not only with the resolution along the range and field of view, but also with the triangulation angle and direction of the normal to the surface, and with defocusing and aperture limitations of the optical system. Moreover, the processing algorithms of light distributions and statistical analysis of measured data are very important. The conditions for undistorted surface reproduction are defined. In the case of violation of such conditions only statistical evaluations of basic surface parameters are possible.
Optical fuzzy sensors
Author(s):
Andrew E. Gorodetsky;
Alexey G. Sergeyev
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A new class of optical devices is proposed -- optical fuzzy sensors, or optical fuzzifiers. The devices make fuzzification process in fuzzy logic controllers easier and faster because convert input crisp data into output fuzzy sets. The optical fuzzy sensors may be used for fuzzy expert systems also.
Height gauging by wavelength-scanning interferometry with phase detection
Author(s):
Jun-ichi Kato;
Ichirou Yamaguchi
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We have realized an accurate step height measurement by using the wavelength scanning interferometry combined with phase- shifting technique. It is based on detection of phase variation slope along the wavenumber axis at each pixel of a CCD camera taking a number of interferograms at different wavelengths and phases. By using a tunable laser diode with wavelength-scanning range of approximately 8 nm, a height deviation of sub-micrometer could be measured by using a PZT phase-shifter. This technique was applied to a height gauging of the gold bump array.
Interferometry method for measuring head-disk spacing down to contact
Author(s):
Xinqun Liu;
Warwick W. Clegg;
Bo Liu
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In this paper, we give a detailed analysis of the working principle, application limits, and potential problems of the intensity interferometry flying height testing, one of the most popularly used flying height testing techniques. Then, a phase-shift method is proposed to improve the sensitivity of this technique when the head-disk spacing is below 10 nm or near contact, based on manufacturing the glass testing disk to have a thickness within specified tolerances. Theoretical analysis and numerical evaluation are presented.
Accurate measurement of the flatness of etalons
Author(s):
Shin-ichi Itoh;
Kentaro Katoh;
Tsuyoshi Oikawa;
Jun Chen
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The method of measurement of two-dimensional flatness of etalons are proposed. Fundamental idea is to measure diameters of interference rings produced on CCD camera. The reproducibility is about (lambda) /1800.
Laser diode optical feedback interferometer for surface measurement outside optical benches
Author(s):
Jiyuan Liu;
Ichirou Yamaguchi
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A simple robust interferometer using a laser diode subject to optical feedback from the interferometer is presented. Fringe phase can be locked by the optical feedback within less than 0.2(pi) (peak to valley value) even when the interferometer is placed outside optical benches where the fringe movement caused by vibration amounts to about 6(pi) (peak to valley value) in the absence of optical feedback. The fringe locking is caused by the change of lasing wavelength that suppresses the net phase change to be much less than 2(pi) . The locked fringe pattern with spatial carries can be analyzed by a fringe analyzer at video rate and the measured results of a spherical mirror showed the same accuracy as on an optical bench.
Surface shape measurement using a wavelength-scanning Fizeau interferometer
Author(s):
Akihiro Yamamoto;
Ichirou Yamaguchi;
Masaru Yano
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We have developed a wavelength scanning Fizeau interferometer for surface profilometry. This interferometer is free from ambiguity of the sign of the resultant profile. It is more compact and robust for disturbance such as vibration than the Michelson interferometer used previously. Experimental results from a step and a dip on mirror surfaces are shown. We could measure a step 1.1 mm high. We also could map a part of a coin but with a noisy result. Origins of the noises are also discussed.
Sinusoidal wavelength-scanning interferometric reflectometry
Author(s):
Osami Sasaki;
Tomokazu Kuwahara;
Ryohta Hara;
Takamasa Suzuki
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We propose an interferometric reflectometry using a sinusoidal wavelength-scanning tunable laser diode to detect positions and profiles of multiple reflecting surfaces. An objective signal extracted from an interference signal contains the modulation amplitude Z and the phase (alpha) which are related to positions and profiles of multiple reflecting surfaces, respectively. By using values of the object signal at special times, we can produce an image intensity which shows where the reflecting surfaces exist. To obtain exact values of Z or values of (alpha) the objective signal is estimated with a conjugate gradient method. Experiments results show that a resolution of two-optical path difference (OPD) in the image intensity is 87 micrometer, and a final OPD accuracy is 2 micrometer and 8 micrometer for the two and three reflecting surfaces, respectively, in the case of the wavelength-scanning width of 7 nm. Profiles of front and rear surfaces of a silica glass plate with thickness of 20 micrometer are measured with an accuracy of about 10 nm.
Novel image processing method applied to speckle fringe pattern based on the wavelet transform
Author(s):
Hong Miao;
Kemao Qian;
Xiaoping Wu
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In this paper, a novel image processing method, the Wavelet Transform based Non-liner Filtering Method applied to speckle fringe pattern (WTNFM), is presented. When traditional image processing methods, such as median filter, mean value filter or FFT (Fast Fourier Transform), are employed to reduce the speckle noise of an image pattern, some useful information will be lost while the noise being removed. For example, the board of the object in the pattern would become blur. The WTNFM, on the other hand, can reduce the loss of information when the speckle noise is removed from the fringe pattern because it can apply different filtering method to the different area of the fringe pattern. It can keep the board of the object in the fringe pattern clear after filtering speckle noise. The principle of the wavelet transform is introduced first, and then a practical algorithm to reduce the speckle noise of a fringe pattern is given. At last part of this paper, a computer simulation result processed by this method is given.
Improvement of precision in the analysis of a lateral shearing interferogram using integration
Author(s):
Seiichi Okuda;
Takashi Nomura;
Kazuhide Kamiya;
Hiroshi Miyashiro;
Kazuo Yoshikawa;
Hatsuzo Tashiro
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In the method for obtaining an error in a shape under test using the integration from a lateral shearing interferogram, it is assumed that the lateral shear of the shape is so small that the interferogram pattern is considered to be representative of the wavefront slope. To obtain the shape, the slope is analyzed by integration. When the lateral shear of the wavefront is not small, an accurate shape cannot be obtained. Furthermore, the analyzed area of the wavefront is limited by the amount of shear, and the whole area cannot be obtained by this method. A method for reconstructing the whole accurate shape from the wavefront analyzed using the integration process is presented in this paper. In a computer simulation to investigate the efficacy of the method, the reconstructed shape agreed with the original shape error.
Absorption change sensor using the transition of states of optical chaos systems
Author(s):
Takuo Tanaka;
Norikazu Shito;
Sadahiko Yamamoto
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We developed an optical absorption sensor using the transition of states of optical chaos system. The developed system utilizes an active interferometer as optical chaos system. We confirmed that the developed system can sense an absorption change of liquid samples. In this paper we describe the theoretical analysis and the experimental results of the system.
Novel film sensor based on p-polarized reflectance
Author(s):
Zhengtian Gu;
Peihui Liang;
Xiaolin Liu;
Weiqing Zhang
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A new scheme of sensor is presented in this paper. The optimization of parameters of the sensor is carried out for designing optical sensor with high sensitivity. By data simulation, the resolutions of nf, kf and df of the film sensor are predicted to be less than 10-7, 10-5, 10-3 nm, respectively. The optical parameters of sol-gel SnO2 film were measured under different dip rates and annealing temperatures, and the sensitivity to the gas C3H8 was investigated. The results indicate that the detection limit is available to 10-1 ppm on the condition of optimum optical parameter and incident angle.
Common-path multichannel heterodyne laser interferometer for subnanometer surface metrology
Author(s):
Feng Zhao;
Jennifer E. Logan;
Stuart B. Shaklan;
Michael Shao
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A multi-channel heterodyne laser interferometer is proposed for measurement of optical surface deformations at the sub- nanometer level. This interferometer employs a common-path configuration and heterodyne detection, by which fringe errors due to laser frequency fluctuations and optical path variations due to vibration can be reduced. By measuring the heterodyne signal phase among sub-apertures (pixels) with a 2- D detector array, the surface height can be reconstructed and surface deformation can be measured by comparing consecutive measurements. Detection of sub-nanometer level surface deformation is achieved using high precision digital phase meters and athermalized opto-mechanical systems. This paper describes the interferometer design criteria and experiment methodologies.
Multichannel averaging phasemeter for picometer precision laser metrology
Author(s):
Peter G. Halverson;
Donald R. Johnson;
Andreas C. Kuhnert;
Stuart B. Shaklan;
Robert Spero
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The Micro-Arcsecond Metrology (MAM) team at the Jet Propulsion Laboratory has developed a precision phasemeter for the Space Interferometry Mission (SIM). The current version of the phasemeter is well-suited for picometer accuracy distance measurements and tracks at speeds up to 50 cm/sec, when coupled to SIM's 1.3 micron wavelength heterodyne laser metrology gauges. Since the phasemeter is implemented with industry standard FPGA chips, other accuracy/speed trade-off points can be programmed for applications such as metrology for earth-based long-baseline astronomical interferometry (planet finding), and industrial applications such as translation stage and machine tool positioning. The phasemeter is a standard VME module, supports 6 metrology gauges, a 128 MHz clock, has programmable hardware averaging, and maximum range of 232 cycles (2000 meters at 1.3 microns).
Nondestructive evaluation of simulated and actual surface defects using a photoacoustic microscope
Author(s):
Haruo Endoh;
Yoichiro Hiwatashi;
Tsutomu Hoshimiya
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Using the specimens of two types with simulated surface defect and the specimen with actual crack, the detection of the surface defect and crack has been demonstrated by photoacoustic microscope. The surface defect of the first type is a group of mutually parallel two defects. The geometry of the second type is the defects crossing orthogonally each other. The specimen of third type is an actual crack. The PA images are obtained for the specimen with double and crossing defects. Furthermore, the detection of actual surface crack has been performed.
Solid immersion lens
Author(s):
Gordon S. Kino
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The diffraction-limited spot size in optical imaging, recording and lithography can be decreased by use of the solid immersion lens (SIL). The simplest form of the SIL utilizes a hemispherical lens with the rays of a focused beam entering along its radii to form a spot at the flat surface of the hemisphere. The spot size is decreased from that in free space by a factor 1/n, where n is the refractive index. If an object to be imaged is placed close enough to the SIL, this reduced spot size is obtained at the disk. In this case the effective numerical aperture of the lens can be greater than one. Applications of the SIL to microscopy, lithography, and optical storage are discussed.
