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- Optical Design and Fabrication
Optical Design and Fabrication
Optical engineering at Keck Observatory: design and performance of the telescopes, adaptive optics and interferometer
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The W. M. Keck Observatory operates two 10-m diameter optical/infrared telescopes on the summit of Mauna Kea (Figure 1) in support of astronomers from the California Institute of Technology, University of California, NASA and University of Hawaii communities. Natural guide star adaptive optics (AO) systems are operational on both telescopes and a laser guide star AO capability has recently become operational on one of these telescopes. The Keck Interferometer, which combines the AO-corrected light from the two telescopes, is currently operational in a visibility science mode, and nuller and differential phase science capabilities are currently under development. This paper will provide an overview of the optical design and performance of these optical systems.
Variable liquid lenses for electronic products
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The design, manufacturing and application of variable liquid lenses are discussed. The interface between the two immiscible liquids that forms the lens can be altered with a voltage. Results are presented of applying this lens in miniature autofocus and zoom cameras, in optical recording and in illumination systems.
Research on the influence of secondary mirror shadow coefficient upon Pan-Cassegrain system
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Pan-Cassegrain (PC) system is a new structure, which originates from the classical Cassegrain system. The most important character of the PC system is that a 4th order aspherical surface, which can be manufactured by using the spherical fabrication technology, is added in front of the primary spherical mirror. The principle of the PC system imaging principle is explained in this paper. And, the correcting lens design of PC system, whose aperture is 300mm and F/# is 10, is studied on conditions as follows: the secondary spherical mirror shadow coefficients are 1/2, 1/3, 1/4 and 1/5, respectively; field angle 2ω=1°. The relations among shadow coefficient, tube length and primary F/# are also analyzed. The results of calculation indicate that, with the reduction of shadow coefficient, the length of system tube will be short, system's aberrations will increase fast, and more correcting lens will be needed. It has a similar character of Cassegrain system and R-C system at this aspect. In practice, choosing an appropriate shadow coefficient is very important in manufacture according to the actual circumstance.
Opto-mechanical integrated analysis for optical system
Baozhong Shan,
Baoping Guo,
Shuyan Wang,
et al.
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High performance optical systems require integrated opto-mechanical analysis to predict performance. But, output from mechanical analysis cannot be used directly by optical simulation. This paper outlines the transmission method of mechanical analysis result to optical program. Zernike polynomials have corresponding meanings of Seidel aberrations and can be accepted by optical program, are used as tool to solve the data transmission problem among optical, mechanical and thermal program. Here, Thermal/Structural/Optical (TSO) integrated process; Zernike polynomials and its fitting method, fitting process are introduced.
Design approach for systems with toroidal optical elements featuring a generalized Scheimpflug condition
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Toroidal elements are special aspheric elements with a missing axial section. Such elements consist of several refractive and/or reflective optical surfaces which are generally tilted with respect to a base ray. This base ray replaces the optical axis in ordinary centered systems. Toroidal elements can be efficiently applied e.g. in LED illumination systems or in optical metrology systems. For these elements there is a lack of design principles, only very few approaches like the Coddington equations are known. In this paper an efficient method is presented that facilitates the design when the requirement or knowledge of the orientation of the image plane is necessary, i.e. where a generalized Scheimpflug condition is needed. In more general terms, the method results in imaging properties of second order expansion, but the method itself is linear. Therefore, the complexity of the design process is considerably reduced. Additionally it is shown how the individual surfaces of the toroidal element can be easily aspherized for sharp imaging omitting tedious optimization. The strength of the design method is demonstrated for a novel application where a complex toroidal element is required for rotationally symmetric triangulation integrated in a vision systems and for a high aperture illumination element based on TIR for LEDs.
Integrated light-guide plates that can control the illumination angle for liquid crystal display backlight system
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Liquid crystal displays (LCDs) with edge-lit backlight systems offer several advantages, such as low energy consuming, low weight, and high uniformity of intensity, over traditional cathode-ray tube displays, and make them ideal for many applications including monitors in notebook personal computers, screens for TV, and many portable information terminals, such as mobile phones, personal digital assistants, etc. To satisfy market requirements for mobile and personal display panels, it is more and more necessary to modify the backlight system and make it thinner, lighter, and brighter all at once. In this paper, we have proposed a new integrated LGP based on periodic and aperiodic microprism structures by using polymethyl methacrylate material, which can be designed to control the illumination angle, and to get high uniformity of intensity. So the backlight system will be simplified to use only light sources and one LGP without using other optical sheets, such as reflection sheet, diffusion sheet and prism sheets. By using optimizing program and ray tracing method, the designed LGPs can achieve a uniformity of intensity better than 86%, and get a peak illumination angle from +400 to -200, without requiring other optical sheets. We have designed a backlight system with only one LED light source and one LGP, and other LGP design examples with different sizes (1.8 inches and 14.1 inches) and different light source (LED or CCFL), are performed also.
Micro electronic and macro optical parameters of the ITO films prepared by DC sputtering for electrochromic applications
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The refractive index (n), the extinction coefficient (κ), dielectric constant ε, free carrier density (nc) and the carrier mobility (μ) of the ITO (Indium-Tin-Oxide) films with different deposition time (or thickness), oxygen partial pressure ratio (PO2) and annealing temperature were measured and studied. The calculated optical parameter-extinction coefficient (κ) was obtained from the diffuse reflectance spectra using "scattering model". The Lorentz oscillator classical model has also been used for fitting the ellipsometric spectra in order to obtain both n and κ values. As comparing the Swanepoel method was used for the refractive index. Clearly the results of the "scattering model", Swanepoel method and Ellipsometric method agree in magnitude. The films prepared at different PO2 show different behaviour of the refractive index and extinction coefficient. The electrical characteristic parameter nc and μ were compared and studied by experimental measurements and calculations using an equation that relates the dielectric function and photo-energy (Drude theory) by Mathematic-4.1 software. Both measured and calculated values coincide in magnitude.
Simplifying the conception of opto-mechanical systems thanks to direct integration of optical design capabilities in mechanical CAD software
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To give optical designers the innovative capabilities that CAD users already have, OPTIS has created the first optical design program fully integrated into a CAD program. This technology called OPTISWORKS Optical Design is available as a plug-in to SolidWorks. It presents multiple advantages for opto-mechanical designers working on projection display systems.
The optical properties of titanium oxide films prepared by dc reactive magnetron sputtering
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TiO2 thin films were deposited on the glass substrates by dc reactive magnetron sputtering technique at different sputtering pressures. The films prepared at low pressures have an anatase phase, and the films prepared at high pressures have an amorphous phase. The optical properties were studied by measuring the transmittance and the ellipsometric spectra. The optical constants of the films in the visible range were obtained by fitting the transmittance combined with the ellipsometry measurements using the classical model with one oscillator. The films prepared at the pressure higher than 6 x 10-3 mbar show a volume inhomogeneity. This volume inhomogeneity has been calculated by fitting the transmittance and the ellipsometric spectra.
Generation of aberration polynomials in a Fourier optical processor using a liquid crystal display
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The objective of this paper was to generate Sidel polynomials using a LCD in a Fourier processor. Our proposal was to use this PCL, due to the fact that it is a small device that does not consume too much energy, with several active elements, and we verified the speed with which it is possible to work with optical processing by changing the images on the screen. Since this system is easy to construct, stable and accessible, we want to use it in the future as a corrector system, due to the fact that it can evaluate the system using a program and with the LCD to try to correct the aberrations that it has.
Hygrothermal design of high stability telescope structure
Deog-Gyu Lee
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Structural and hygrothermal analysis for a composite tube is carried out in this study, that provides critical parameters for the design of a highly dimensionally stable space telescope. Carpet plots for laminate effective engineering constants are generated and used for the best tube lay-ups with high elastic modulus and highly insensitive to thermal and moisture expansion, which is essential for maintaining optical alignment of opto-mechanical system under random force applied during a launch campaign and orbital thermal load. Despace in the longitudinal direction under hygrothermal load of the tubes constructed with the selected lay-ups is calculated for the validation of lay-up designs on the dimensional stability. Dynamic analysis is also carried out to feature the resonant behaviour. A zig-zag triangular element accurately representing through thickness stress variations for laminated structures is developed in this study and incorporated into the structural and hygrothermal analysis.
Design and fabrication of W/Si multilayer mirrors for the K-edge of Ti
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The periodic mulitlayer with high reflectivity and small full width at half maximum (FWHM) in hard x-ray range, while the reflectivity of non-periodic multilayer decreases and FWHM increase. Therefore, the optimum coating design must be found out as a compromise between the requirements for the reflectivity and the FWHM. We have used purely numerical techniques to design broad angular multilayer mirror in angle intervals (2.9°-3.1°), which is starting from an appropriate periodic multilayer structure. In our method, the risk of local minimization of the merit function disappears, because we refined the desired depth-distribution of the period using a direct numerical algorithm and the analytical solution as a starting point for computer calculation. The plateau reflectivity can be obtained in a few minutes. The main feature of our approach is the use of an analytical solution as a starting point for direct computer search, and the desired results can be given in a reasonable time. This technique is able to design almost any given reflectivity spectrum both energy- and angle-dependent and in a reasonable amount of time. The periodic and non-periodic W/Si multilayer for grazing incidence multilayer mirrors at the K-edge of Ti (0.275 nm) were both designed and fabricated by high vacuum DC magnetron sputtering coater model JGP560C6, and the multilayer films were characterized by X-ray reflectivity measurements on a laboratory x-ray diffractometer(XRD) and the atomic force microscope (AFM). We find good agreement of the changing trend of surface roughness between the simulation of XRD and measurement of AFM.
Current research activities in the field of multilayer for EUV, soft x-ray and x-rays in IPOE
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The present status of studies on EUV, soft x-ray and x-ray multilayer in the Institute of Precision Optical Engineering (IPOE) is briefly reviewed. With the aim of realizing a Mach-Zender interferometer working at 13.9nm, we have developed a semitransparent beam splitter with multilayer deposited on the back side of a silicon nitride membrane. On the basis of the experimental optical properties of the beam splitter, design has been performed to define the multilayer
structure that provides the highest product of reflectivity and transmission. Optimized Mo/Si multilayer has been successfully deposited on the back side of a silicon nitride membrane by use of the magnetron sputtering. Measurements by means of a reflectometer in Beijing Synchrotron Radiation Facility at 13.9nm and at an angle of 7.2° provide a reflectivity of 20% and a transmission of 22%. Such a beam splitter has been used for X-ray Mach-Zender interferometer at 13.9nm. The broadband multilayer analyzer in the range between 12.4nm and 20nm is designed, and made which can deviate the Quasi-Brewster's angle several degree and show very high polarization. The main feature of our design approach is the use of an analytical solution as a starting point for direct computer search, and the desired results can be given in a reasonable time. The method can be applied in different spectral range for suitable material combination. Supermirrors with broad angular band working at different wavelength such as Cu Kα line are designed, manufactured and measured. The results show that the performance of the supermirrors is in agreement with designed data.
Optical thin films for high power LD-pumped Nd: YVO4 457 nm blue laser
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The expanding field of LD-pumped solid state lasers forms an extraordinary challenge for developing the optical coatings. Optical thin films for LD-pumped Nd:YVO4/LBO blue laser at 457nm was presented in this paper based on lower gain laser line action theory, including spectral beam dividers and doubling antireflecting multilayer coatings. To achieve 914nm laser action and 457nm blue light high output power, the coating specifications of laser resonator was analyzed. The transmittance/reflectance spectrum request was effectively separated by adopting high tuned radio stack, simultaneously the spectrum request was reasonably distributed on the two resonator facet reflectivity for restrain the other laser lines such as 1064nm and 1342nm. The dielectric high reflective laser mirror and antireflecting coatings for 457nm laser were manufactured by double ion beam sputtering technique, which is controlled by a time-power monitoring. Using type-I critical phase-matching LBO crystal, 457nm blue laser is obtained by 914nm intracavity frequency doubling. The maximum laser output power of 1.5W is obtained when incident pump laser of 15W is used.
Design of primary mirror for laser beam director
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We designed the laser beam director (LBD) with the radius of the primary mirror of 800mm, the focal length of 8,000 mm, and F-number of 10. To design the light weight primary mirror for the LBD system, we considered the primary mirror of double arch shape with parabolic contours, the maximum thickness of 120 mm, the outer edge mirror thickness of 15mm. The considered axial support system was six equally spaced supports at 60 degrees and the radial support
system was three equally spaced supports at 120 degrees. Considered material properties were the elastic modulus of 9.06×1010N/m, the poisson's ratio of 0.24 and the weight density of 2.53 g/cm3. A finite element model with 1,512 nodes was selected for structural analysis. In order to examine the validity of the closed-form solution for the primary mirror
with a double arch shape, the primary mirrors of various contoured back shape equations with support ratio ranging from
0.5 to 0.8 were used. The considered support radii were 200, 240, 260, 270, 280, 290, 300, 310, and 320mm. We found that the deformation of the primary mirror for horizontal axis decreases, as the support ratio increases. The smallest deformation of primary mirror for zenith axis was given when the support ratio was 0.675. For this case, the P-V value was 27.810nm and the RMS wave error was 0.0160λ. We were also able to determine from the structural
analysis that the optimum support ratio of the primary mirror for the LBD was 0.75.
Key techniques of laser direct writing of fine lines on the spherical surface
Fengchao Liang,
Jun Hu
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The main principles of laser direct writing (LDW) system for lines on the spherical surface (SS) are discussed. It is pointed out that line profile is determined by the exposure dose distribution, which lies on the light intensity distribution of focus plane and the scanning speed. To improve the quality of line profile on the SS, several key techniques as follows are introduced. Firstly, the unique system configuration, four axes mutually intersecting at the center of the SS, is adopted, which ensures the shape of the focus be maintained circular during the writing period. Secondly, an automatic focus system (AFS) with the function of automatic focus in a certain range is introduced. Thirdly, to guarantee the linear velocity to accord with the exposure character of the photoresist all the time, an efficient arithmetic that controls motors run at appropriate angular velocity in different latitude is developed. Finally, to achieve a stable and well-behaved system so as to compensate the velocity instability resulting from unavoidable errors of mechanical and electronics factor, a powerful programmable multi-axis controller (PMAC) is utilized as the kernel element of the servocontrol system, and the curves of step response and parabolic response achieved by feedforward and PID loop tuning indicate that the location precision and velocity stability have reached a high level. The experimental results of LDW of lines on the SS work piece with a diameter 30 mm and a radius equal to 100 mm are given. The section analysis of the lines on the photoresist by the atomic force microscope (AFM) after exposure and development is performed. The results show that line width is about 3.0 μm, and the steep sides of the lines are parallel to each other.
Surface/subsurface observation and removal mechanisms of ground reaction bonded silicon carbide
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Reaction Bonded Silicon Carbide (RBSiC) has long been recognized as a promising material for optical applications because of its unique combination of favorable properties and low-cost fabrication. Grinding of silicon carbide is difficult because of its high hardness and brittleness. Grinding often induces surface and subsurface damage, residual stress and other types of damage, which have great influence on the ceramic components for optical application. In this paper, surface integrity, subsurface damage and material removal mechanisms of RBSiC ground using diamond grinding wheel on creep-feed surface grinding machine are investigated. The surface and subsurface are studied with scanning electron microscopy (SEM) and optical microscopy. The effects of grinding conditions on surface and subsurface damage are discussed. This research links the surface roughness, surface and subsurface cracks to grinding parameters and provides valuable insights into the material removal mechanism and the dependence of grind induced damage on grinding conditions.
Polarization properties of thin-film-coated prisms
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Thin-film-coated prisms are used widely in optical systems. This is because that they not only provide a convenient and efficient means of light-beam deviation, but also have special polarization properties. Polarization effect is one of the most important factors affecting the performance of optical systems. Thin-film-coated prisms play an important part in the optical systems because of their special polarization properties. In this paper polarization properties of thin-film-coated prisms are analyzed as general polarization elements and two examples are given. The polarization properties of the prisms mainly lie on the thin films coated on the interfaces. One example in this paper is the design of using a thin-film-coated totally reflecting corner prism to produce quarter-wave phase retardation. Another example is the design of using a thin-film-coated beamsplitter cube prism to cancel the unwanted polarization effect. According to the analysis of the polarization properties of thin-film-coated prisms, we can draw a conclusion that it is an effective method to use thin-film-coated prisms to get the desired polarization state or to control the polarization effect in optical systems. Furthermore, optical thin film system coated on optical interfaces has a profound effect on the polarization properties of optical elements. Therefore, optical thin film designs should be considered carefully while designing optical systems.
Mode analysis of the UV-written channel waveguide
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The effective index method (EIM) was adopted to model the channel waveguide patterned by the UV in photosensitive silica film. The effective indexes of the different dimension symmetrical and asymmetrical channel waveguides were calculated, and the resource of the error of the method was pointed out. At last, the dimension rang to propagate single mode was presented.
Application of maximum entropy principle in plane lapping
Xusheng Zhou,
Shengyi Li
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With technology developing, there are increasing demands for the high-quality optical elements, as well as the related processing techniques and equipments. The plane lapping tool uses a rotating tool which overlaps the workpiece surface. By accurately controlling processing parameters, a prescribed amount of material may be removed at each point on the surface. Thus the key for us to increase lapping accuracy of optical elements is to select the optimal processing parameters. In this study, the technique of ultra-precision plane lapping is the subject. A method based on maximum entropy principle is presented to express the lapping effect and optimize processing parameters in plane lapping. We aim to provide valuable scientific foundation for improving present processing techniques and equipments and finally to increase machining accuracy and efficiency. In this paper, mathematic formulation and corresponding physical explanations for the lapping entropy are established. Moreover, the processing parameters in eccentric plane lapping are computed. The computational results show that in eccentric plane lapping the same rotational speed of the workpiece and lapping tool should be selected to remove material equably, and that a rather large eccentricity ratio should be selected to increase lapping efficiency. To reduce the influence of the wear on lapping accuracy, the lapping tool should be refaced on real time. The optimization method we have used possesses advantages of simplicity, intuition and generality. Using the optimized parameters, we have successfully fabricated a SiC workpiece whose flatness error has reduced from 1.9 μm to 0.18 μm in a short time.
Novel computer-aided alignment method of optical systems based on genetic algorithm
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The essence of computer-aided alignment (CAA) is to find a solution to the inverse problem of a designed optical system. A novel method to solve the misalignments of optical systems based on genetic algorithm (GA) is proposed in this paper. The method of real-coding and multi-operators parallel style is used to improve the precision of result and to maintain the variety of population. The hybrid algorithm that incorporated GA with DLS (damped-least-squares method) are used to invert CAA model. The solution obtained by GA is a starting point for DLS . The results of numerical simulation prove that this method significantly improves the accuracy of the solution and accelerates the convergence to global optimum, and behaves with strong robustness and reliability.
Design and analysis of x-ray microscope of four mirrors working at grazing incidence
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In the latest 20 years, x-ray imaging technology has developed fast in order to meet the need of x-ray photo-etching, spatial exploration technology, high-energy physics, procedure diagnosis of inertial confinement fusion (ICF) etc. But, Since refractive index of materials in the x-ray region is lower than 1, and x-ray is strongly absorbed by the materials, it is very difficult to image objects in the x ray region. Conventional imaging methods are hardly suitable to x-ray range. Generally, grazing reflective imaging and coding aperture imaging methods have been adopted more and more. In this paper, non-coaxial grazing reflective imaging KB and KBA microscope systems are discussed in detail, and an x-ray microscope consisting of four mirrors working at grazing incidence is designed. It is an anastigmatic system, and the oblique angle of the image is evidently decreased. The resolution of 5-7 can be obtained within 2 field of view. And finally we also make analysis of the key problems that are met in the processing of manufacturing this system are analyzed.
Characteristic-analysis of optical low pass filter used in digital camera
Tingyu Zhao,
Rong Wang,
Yuling Liu,
et al.
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Optical Low Pass Filter (OLPF) is composed of several birefringent crystals (e.g. three quartz-crystals). A light spot can be separated into several divergent light spots after passing OLPF. This characteristic can be widely used in digital camera and other image-forming system. The imaging beam in practical use is wide spectral and convergent, which causes dispersion and deformation. This paper hereby analyzes and simulates the characteristics of frequency response, dispersion and broad-angle-incident of the OLPF in theory and in experiment. Firstly, several birefringent crystals with proper alignment are introduced into OLPF to get a better frequency response. Compared with the OLPF with one crystal, its side-lobe is suppressed to a great extent without obvious deterioration in the main-lobe. Secondly, although the original dispersion is already acceptable according to optical aberration allowance, the maximum dispersion can be reduced from 8.49% to 5.66% of the pixel-pitch of CCD by changing one of the crystals from positive crystal (quartz) to negative crystal (e.g. calcite) with the same frequency response. Thirdly, broad-angle-incident is analyzed and simulated as a further research. Suppose a conical beam which converging at the CCD passes a birefringent crystal, a circle and ellipse-like faculae instead of two circles will be got. The error is less than 25% of the ideal offset when the incident angle is as large as 14o. The OLPF with two or three crystals can be analyzed in the same way. The characteristics analyzed above are coincident perfectly with simulation in Tracepro and experiment results. Consequently, regular OLPF can meet the requirements of wide spectral range and broad-angle-incident optical system.
Optical and local current studies on InAs/GaAs quantum dots
T. X. Li,
P. P. Chen,
F. Z. Wang,
et al.
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By optimizing the growth technique of molecular beam epitaxy (MBE), we've prepared high quality InAs quantum dot samples, with high density (up to 1.2 x 1011 cm-2) and highly homogeneous size. Strong room temperature photoluminescence (PL) have been observed. The PL study reveals four confined-states QD transitions, which shows filling effect of the excited states. Dependence of these recombinations on excitation intensity and temperature has also been investigated.
Conductive atomic force microscopy (C-AFM) has been used to probe the local current of InAs surface quantum dots (SQDs) on doped GaAs layer. It is found that current about picoampere can be drawn from individual QD while bias of a few hundred mV is applied between tip and the sample. Further I-V studies discover that surface quantum dots usually has a threshold bias near 200 mV for current transmission, whereas bias of 400 mV is needed when the conductive tip is located on wetting layer.
A novel method for fabricating periodic micro domain structure in a ferroelectric crystal using a femtosecond laser
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A novel method of fabricating a periodic micro domain structure in ferroelectric crystal by using two interferential kHz femtosecond laser beams is proposed. Some experimental results and discussion were given.
3D photoresist etching simulation using cellular automata
Zai-Fa Zhou,
Qing-An Huang,
Wei-Huan Li,
et al.
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The two-dimensional (2-D) dynamic cellular automata (CA) model, for the first time, has been successfully extended in three dimensions for the 3-D simulation of photoresist etching process. The 3-D photoresist etching process has been successfully simulated using the 3-D dynamic CA model when some well-known photoresist etch rate distribution functions are adopted. Simulation results indicate that the 3-D dynamic CA model is fast, accurate and stable. This is identified to be critical useful to the device-sized 3-D lithography process simulation of integrated circuits (IC) and Microelectromechanical System (MEMS).
Optical damage computer generated holograms
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In this work we demonstrate direct writing of a computer generated hologram using optical damage in glass as a possible recording process. The recording was performed by ablation in BK7 optical glass. We used a 10 Hz, 35 picoseconds, 5 mJ Nd:YAG pulse focused using a lens to create 50 μm spots. It was observed that the material surrounding the damage spot was altered producing a 70 μm minimum pixel resolvable separation by induced birrefringence.
The optical design of stereo endoscope
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Stereo endoscope has played an important role in video 3-dimensional laparoscopy system. This paper presents the design principle of the stereo endoscope applying in minimal invasive surgery (MIS). Optical imaging technologies and instrument designs are discussed in relation to their current and future use in MIS procedures, then this paper analyses and compares three design methods of optical system, technical limitations in imaging technology are described along
with potential solutions. We put forward to a new optical design methods, namely, the system adopts two optical channels stereoscopic-imaging technique to replicate human binocular vision. A stereoscopic system for video endoscopes includes objective lens system, relay system, eyepiece system and the focused lens between eyepiece and
CCD. This paper present equal-angle pairs from symmetrically disposed object points to the system. This equal-angle property enables accurate object/image mapping onto the final stereo image pair. And the doctors can watch the true stereo image on the screen. This optical system has common characteristic compare to the common laparoscopy with long work distance-300mm and wide field-70 degree, as a result, the optical system have serious aberration related field, especially in distortion, the distortion can reduced from 15% to 5%.
Solution strategy of optimal dot pattern design for light guide using in backlight
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This paper proposes a solution strategy for the optimal design of the dot pattern located on light guide plates used to illuminate LCD displays. The proposed dot pattern optimization procedure is based on a geometrical dot area ratio parameter, which is strongly related to the physical luminance properties. Compared to conventional optimization procedures, the use of this parameter minimizes the number of dot pattern parameters which must be considered simultaneously when developing the optimal dot pattern design. The proposed design method utilizes the simple false position method to determine the optimal dot area ratio for each individual section of the light guide. Two regulation methods are then proposed to fine-tune the dot radius and the dot spacing, respectively, in an attempt to achieve uniform-luminance conditions across the complete light guide. The validity of the proposed solution strategy is confirmed through a series of simulations. Compared to other optimization procedures, the proposed solution strategy has the significant advantage of being readily implemented into existing optical commercial programs.
Writing system for digital documents reader
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We proposed an optical system called ACOAS as a scanner in two dimensions and we present the analysis to first order
and the final optical design for two versions, glass and plastic versions, this scanner will be used as a writing system for
a digital documents reader. The image quality fulfills the requirements because the final designs are diffraction limited
systems.
Optical and hydrophobic nano-porous silica thin films with low refractive index
Lanfang Yao,
Yongan Zhu,
Dian Qu,
et al.
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Optical and hydrophobic nano-porous silica films with low refractive index were prepared by means of a two-step acid-catalyzed method and sol-gel process using surfactant CH3 (CH2) 15 N(CH3)3 Br (CTAB)as template, with a simple dip-coating procedure. Methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) were co-hydrolyzed in different molar ration and were used as precursors. The process was optimized by varying MTES / TEOS ration, sol aging, thermal treatment and dip-coating conditions to obtain good optical films with low refractive index. The infrared spectra of the films thus obtained indicated that they become hydrophobic with the introduction of the methyl groups. Contact angle values for optical hydrophobic films prepared are greater than 120 degree supplementing the result. The refractive indices and thickness of optical films are about 1.12-1.21 and about 300-440 nm according to different MTES / TEOS ration of 0.2-0.8 using CTAB (2.5 wt%)at 400 degree thermal treatment by Ellipsometry. AFM of the films provide an estimate of the root-mean-square roughness of the surface to be 312(pm). The optical transmittance spectra and mechanical intensity measurement results showed that the films have good optical and mechanical properties. As a result, the moisture-resistant ability of the films was highly improved and the mechanical intensity was improved too.
Experimental results and wear predictions with free-pinned petal tools
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The wear produced by free-pinned tools is difficult calculate, since their angular movement is not entirely predictable. First, we analyze the wear produced with free-pinned ring tools using both simulations and experiments. We conclude that the wear of an incomplete ring is directly proportional to its angular size, independently from the mean radius of the ring. Second, we present an algorithm for the calculation of the wear produced by free-pinned petal tools, since they can be considered as a linear combination of incomplete free-pinned ring tools. Finally, we apply this result to the enhancement of a defective flat surface and to aspherate a concave spherical surface.
Study of CVD SiC thin film for space mirror
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The performance of space mirror lied on the properties of the mirror surface material to a great extent. In this paper, the silicon carbide thin film deposited on reaction-bonded silicon carbide (RBSC) space mirror blank was produced by Chemical Vapor Deposition (CVD) process. Some mechanical and physical properties of the SiC thin film were tested because they were important to study ability to work of space mirror. The result of XRD phase analysis indicated that the component of the SiC thin film was β-SiC. The micro hardness of the film was tested. The thickness of SiC thin film was tested using needle touch contour graph. The results showed that the thickness of SiC film was about 20 μm and film was even in the macro scope. The adhesion strength of SiC thin film and RBSC substrate was tested by scratch method and the results showed that was excellent. The residual stress of SiC thin film was tested by X-ray, at the same time; the origin of residual stress and the calculation of thermal stress were discussed. In the room temperature, the residual stress of the SiC film was compressive. After precision grinding, the surface topography and roughness of the SiC thin film was tested by Atomic Force Microscope (AFM). The results showed that the surface of SiC thin film had extremely low surface roughness and high surface form accuracy. The thermal shock resistance of SiC film was fine by tested.
Medium precision optical testing of a fast concave elliptical mirror by a cylindrical null screen
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We extend the principles of the null screen method for testing a fast ellipsoidal concave mirror by designing a null cylindrical screen, located around the near focal point of the ellipsoid (being parallel to the optical axis) and the observing CCD camera is near the far focal point. We present the formulae to design the screen in such a way that the image on the CCD is a perfect square grid; the departures of the surface from a perfect ellipsoidal shape are observed as deformations of the grid in the image. We show qualitative experimental results.
Lie algebraic treatment of optical systems in higher aberration orders
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Using the technique of Lie operator algebra, we present a recursive formulation for calculating the third and fifth order aberrations of a general optical system and express the third and fifth order aberration coefficients in the 7×7 and 12×12 matrix forms, respectively. One advantage of our formulae is their explicit algebraic expressions suitable for practical application and numerical calculations, another is that the formulae provide a formulation of the matrix method for general nonlinear transformation and the generalized matrix method employing Lie algebraic tools proposes a new view for aberration optics computation. With the method it should be possible to evaluate all the aberration terms for any optical system. Applications of the matrix method are illustrated with thick lens and some well known imaging systems.
Effect of UV-irradiation on sol-gel optical films
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Sol-Gel optical film was widely used in high power laser system with the development of its preparation technique. Ultraviolet treating is an effective method to solidify the film and improve its performance. In this paper, optical films were deposited on K9, silica glass and silicon wafer substrates by Sol-Gel spin-coating method and ultraviolet light source was produced by 1000W high-pressure mercury lamp to irradiate these optical films. SEM, AFM, IR and ellipsometer were used to characterize the structure and optical properties of the films. Mechanical property of films was measured by pencil hardness-testing device. Laser damage threshold of films was measured by a Q-switched Nd:YAG high power laser whose wavelength was 1064nm and its pulse width 15ns. The results show that UV-irradiation can improve the mechanical property and increase the refractive index of the films. The nodules on the film surface can be changed into pits by UV-irradiation process so the laser damage threshold of Sol-Gel thin films increased. The laser damage threshold of ZrO2 single-layer film added with PVP reaches 50.6J/cm2 (1064 nm, 1 ns) after UV-irradiation process. It was found that UV-irradiation is an effective method to avoid infiltrating between the layers and improve the homogeneity of the multilayer films. The reflection of 5 layers of ZrO2/SiO2 multi-layer films is increased more than 10% after UV-irradiation treatment.
Two novel methods for liquid refractive index or concentration measurement using reflex fiber optic sensors
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Two novel content meters for liquid refractive index or concentration measurement are proposed based on the simple reflex fiber optic sensor configurations. One sensor exploits a reflex and concentrically arranged fiber probe structure which is very similar to the traditional intensity-modulated fiber optic displacement sensors, but the light captured by receiving fibers is modulated by the varied solute concentration, being in proportion to the liquid refractive index, instead of displacement. The other sensor works based on detecting the edge shift of the reflected light spot, which is modulated by the refractive index variation of the liquid. Theoretical analysis and simulations are carried out with the measurement range of refractive index from 1.0 to 1.5.
Theoretical analysis and improving method for the contrast of image under water
Jing-hua Sun,
En-fang Sang
Show abstract
On the basis of scattering theory of Ocean Optics, the theoretical formula of the contrast of image under water is derived in this paper. In addition, a method for improving the contrast of image under water is put forward. Experiments of using symmetrical double light sources have been conducted, and show that the contrast has been improved more than twice of that using single light source. Theoretical results are in agreement with that of the experiments. Both theoretical and experimental studies reported here show that the symmetrical lighting system is an efficient method to improve the contrast of image under water.
Novel methods for measuring modulation transfer function for fiber optic taper
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As a relay optical component, fiber optic taper has become more important and more widely used in the integrated taper assembly image intensified sensors for military and medical imaging application. However, the method for evaluating the quality of output images from the fiber optic taper is few. In this article, the Modulation Transfer Function (MTF) is introduced and measured to evaluate the image quality of fiber optic taper. Because fiber optic taper is of a mosaic array architecture, there are some new problems need to be resolved in defining MTF of it. And there also should be some special requirements in MTF measurement. Two methods including edge scanning and point imaging analyzing are introduced in measuring MTF of fiber optic taper, in which the incident light, scanning step and scanning range are specially limited. Experiments show that the results of the measurements consist with the theoretical analysis simulated by computer. And the spatial averaged MTF of fiber optic taper has been gotten by two means. It is concluded that the MTF value measured by point imaging is always some higher than measured by edge scanning, because the point imaging is more weakly effected by the fiber arrangement in taper.
Sol-gel coating of transparent optically variable
Xingyuan Ni,
Zhihua Zhang,
Fan Yang,
et al.
Show abstract
A sol-gel coating of transparent optically variable is introduced in this paper. The plastic films coated with titanium dioxide using sol-gel process were embossed to form special patterns in micrometer scales. AFM, SEM, ellipsometer and electrophotometer were used to characterize the TiO2 coating and the transparent optically variable. The results show that the titania coating has nano-porous structure and the refractive index is about 1.9. The diffraction efficiency of the transparent optically variable coating is about 2.0%.
Study of infrared AR and protection coating on MgF2
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Infrared AR and protective complex film is coated on the MgF2 substrate associated with ion source aid technology. The complex film is composed of multilayer dielectric film and super hard protective film. The function of dielectric film is antireflection while the super hard film is used as protective layer. Through analyzing the stress match, bond strength and binding force which exist between film and substrate as well as among layers, optimum materials are selected. Efficient antireflective and protective function are realized when the best technological parameter is chosen. The result of the experiment indicates that the reflection of single facet is reduced from 2.5% to 1.5%. Moist and thermal test as well as high and low temperature test have passed. The synthetic result of the experiment is also provided.
Optical coatings optimization of semiconductor laser
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The characteristics of GaAs-based semiconductor Laser with antireflective and high reflective coatings are studied. The film designs are optimized with programmed software using the film design program for a double-layer scheme. According to the numerical simulations, the different double-layer with proper parameters is coated onto GaAs-based semiconductor Laser. The thickness of double layers is also calculated using the software taking account of antireflective and high reflective coating in the design of double layer film. With the optimized design of double-layer film, the power properties of GaAs-based semiconductor Laser are improved, and the experimental results satisfy the application requirements as semiconductor Laser.
Design and fabrication of the broadband x-ray supermirrors
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The broadband x-ray supermirrors have been designed, fabricated and studied experimentally. They are intended for operating in the photon energy range from 12.4 to 20keV at the fixed grazing incident angle of 0.5°. The choice of material pairs composing a non-periodic multilayer structure is considered from the maximum achievable reflectivity and the layer structure stability. Tungsten and silicon are selected, which have the great index contrast in this energy range and are suitable for fabrication with the use of the vested coating system. The interface width determined by transmission electron microscopy (TEM) lies in the range of 0.4~0.6nm. Following a theoretical approach including analytical and numerical techniques, the designed multilayer mirrors have a practically constant reflectivity of about 24% in the desired photon energy range. The multilayers were deposited onto polished silicon substrates by a high vacuum DC magnetron sputtering system and were characterized by x-ray diffractormeter (XRD) at 8.0keV. The experiments show that the sample has about 10% reflectivity in a wide angular range; The roughness of the interface for both tungsten on silicon layer and silicon on tungsten layer was estimated to be about 0.5nm. Oscillations in the reflectivity curve proved to be larger than the expected ones. They may be caused by the random variation of the layer thickness, as well as the interdiffusion between two materials. Possibilities for further improvements of wideband multilayer mirrors are analysed as well.
Design of soft x-ray multilayer polarizing elements
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The status of polarizing optical elements for the soft x-ray range is reviewed. The criteria for optimum polarization of soft x-ray reflective analyzers, transmission polarizers and phase retarders based on multilayer interference structures are presented. Following these principles, soft x-ray polarizing optical elements have been designed. Designs of broad angular and wavelength range reflective analyzers based on a combination of analytical and numerical methods are also discussed.
Circular gratings based on binary optics and their diffraction computer simulation
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This paper presents a novel method to fabricate circular gratings based on binary optics. A smart digital micro-mirror device (DMD) laser writing system is used to fabricate circular gratings. By use of the DMD system, we are capable of making low-cost and useful circular gratings easily. Their levels and radii can be controlled and be suited for many optical systems. Experiment results have been obtained with two and four levels. In this paper, it will also show a method of simulating circular gratings' diffraction. Using the simulation method, we can value and check the diffraction effect of circular gratings to rectify the design parameters.
The influence of the secondary mirror position and the lightweight primary mirror on optical performances
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To design a laser beam director (LBD), we considered the ritchey chretien system with a hyperbolic mirror surface. The aperture sizes of the designed primary mirror and secondary mirror were 800 mm and 120 mm, respectively, and the obstruction ratio was 0.3.
Energy distribution on the target surface was studied in terms of a spot diagram and encircled energy in order to investigate the optical performance of the LBD system. As the LBD system was designed to focus on the various positions of target by varying the position of the secondary mirror, we developed the computer program called LOSA (Large Optical System Assessment) to investigate the influence of the position of the secondary mirror on optical performance.
To reduce weight of the primary mirror of the LBD, we also considered the primary mirror of a double arch shape with parabolic contours. Deformation of the primary mirror caused by gravity was not rotationally symmetrical about the mirror axis. We also used the LOSA program to analyze the influence of the light weight primary mirror on optical performance, and finally determined the optimum structure of the primary mirror.
Research on geometric model of grinding large and medium scales optical aspheric surfaces
Nianhui Kang,
Shengyi Li,
Ziwen Zheng
Show abstract
Aspheric optics have been used in optical systems widely because of their excellent optical properties. At present, the manufacture of small scale aspheric surfaces has been industrialized. However the manufacture of large and medium aspheric surfaces still follows the procedure of grinding, lapping and polishing. Generally speaking, increasing the working efficiency is the key of machining large and medium scale aspheric surfaces. As we know, lapping and polishing have relatively low efficiencies. Therefore prior to lapping and polishing, NC grinding is often used to shape large and medium scale optical aspheric surfaces, so as to reduce the subsequent process time. Current approaches to grinding aspheric surfaces differ from each other because the wheels and methods used are different, which is inconvenient for programming. To facilitate programming, a unified mathematical formulation is proposed for calculation of the wheel center trajectory when grinding axisymmetric aspheric surfaces based on the principle of shaping aspheric surfaces. Certain geometric models are derived from the unified formulation for the cases of parallel grinding wheel, spherical grinding wheel and cup grinding wheel, according to their features of process. The condition of avoiding overcutting is also derived. The step length of cutting is adaptively selected with accuracy control so as to reduce the program codes. After analyze all the factors affecting the shape accuracy of the curved surface, the major factors are found to be the tool setting error and the radius error of the grinding wheel, then the corresponding influence coefficients of the errors are calculated and the simulation results are given. Finally an example is shown in order to prove the analysis.
Theoretical analysis of optical properties of dielectric coatings dependence on substrate subsurface defects
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A model for refractive index of stratified dielectric substrate was put forward according to theories of inhomogeneous coatings. The substrate was divided into surface layer, subsurface layer and bulk layer along the normal direction of its surface. Both the surface layer (separated into N1 sublayers of uniform thickness) and subsurface layer (separated into N2 sublayers of uniform thickness), whose refractive indices have different statistical distributions, are equivalent to inhomogeneous coatings respectively. And theoretical deduction was carried out by employing characteristic matrix method of optical coatings. An example of mathematical calculation for optical properties of dielectric coatings had been presented. The computing results indicate that substrate subsurface defects bring about additional bulk scattering and change propagation characteristic in thin film and substrate. Therefore, reflectance, reflective phase shift and phase difference of an assembly of coatings and substrate deviate from ideal conditions. The model will provide some beneficial theory directions for improving optical properties of dielectric coatings via substrate surface modification.
A review of the fabrication of optic fiber
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In optic communication field, fiber is the most adoptive material, as it is endowed with well performances in optic communication, amplifier, sensor, power delivery and so on. In this paper, species of fiber and their main applications are introduced, then, the invention and subsequent development of main methods for making optical fibers are reviewed and compared, with the ordinary vapor deposition methods of MCVD, PCVD, VAD, OVD, all kinds of casting methods, direct drawing method of two-crucibles, extruding methods to SCF and POF, special fabrication methods to optic fibers or hollow wave guides.
With the newly arisen fibers of PCF, SMNWs, there are also some descriptions about their main principles, fabrication methods and future development. In conclusion, some optimism predictions of fiber are drawn out based on the requirement of wide-band communication and optic wave-guides technology.
Optimization of high-numerical-aperture objectives by splitting a singlet with control of higher-order aberration
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A scheme is proposed for the automatic control of higher-order aberrations during the course of lens optimization, as well as third-order aberrations. First, the singlet with the larger paraxial marginal ray slope difference is modified into a doublet. The doublet is combined with two elements, for which their refractive index difference is selected to be small, instead of the traditional combination with the crown and flint glasses. And the middle surface in the doublet will give a variably controllable higher-order aberration contribution to the image quality, whereas the third-order aberration is comparably fixed, so that the "system aberration balance" would be achieved in the optimization run. The optimization of a photographic objective is investigated using this method. The design result can provide good image quality. Results of manufacturing simulations are also given for the systems, which show that the optical system optimized with our scheme can be successfully fabricated.
Two absolute photonic gaps from 2D square compound lattices
Min Zhu
Show abstract
The photonic band structures of two-dimensional square compound lattices are calculated by the plane-wave method. Two same dielectric cylinder embedded in a background of air are located symmetrically at both sides of each square lattice site. Two absolute photonic band gaps common to E and H polarized waves are created when given proper structure parameters.
Random and non-overlap dot generation for light guide used in LCD backlight by molecular dynamics method
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The random dot pattern generation by the use of molecular dynamics (MD) is proposed to the light guide design used for the backlight. Several numerical techniques are developed to provide the great advantage for the combination the subsequent optical optimization for the dot density adjustment satisfy the uniformity requirement demanded by the LCD display. The cell divisions technique is proposed, which allows the dot density adjustment within each cells dividing from the light guide. In addition, the technique is developed to account for different cells to localize the repulsive force acting within the cell to achieve high dot density gradient in the dot distribution. Moreover, the average force control technique is developed to handle the uniformity of dot distribution across the cell boundary. Finally, several illustrations are included to show the validity the robustness of the proposed MD dot generation algorithm.
Estimate luminance of single panel and dual panel light guide by luminous flux flow
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This paper presents a mathematical method to estimate luminous flux and luminance of single panel and dual panel light guides based on photometric calculations under various design requirements. The distribution of dot pattern or micro-prism was computed according to those estimated luminous flux on the illuminant surface. The effects of light source efficiency, angular distribution of luminance of light guide, luminous flux ratio and area ratio of main panel with sub panel on luminance of light guide are discussed. The relationship between luminous flux and luminance was derived for single panel and dual panel light guides. For single panel light guide, the result reveals that the angular distribution of luminance of light guide affects the luminance obviously. The luminance increases as the cone angle (the range of angular distribution of luminance) decreases. For dual panel light guide, the luminous flux of three different areas, two located at main panel and one located at sub panel, are the functions of angular distribution, luminous flux ratio and area ratio. The luminance of main panel and sub panel were estimated and computed from mathematical functions. The optical properties of dot pattern and micro prism or other optical objects were used to determine the luminous flux ratio and then the difference luminance between main panel and sub panel was estimated. This estimation strategy provides a fast initial design and the solution to predict the luminance of single panel and dual panel of light guide.
Applications of reverse engineering in the fabrication of optical coatings with high performance
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"Reverse Engineering" attempts to derive information about the makeup of an existing optical coating from optical spectrum measurements, usually of performance, which can be converted into targets for inverse optimization synthesis. In the method of inverse synthesis, optimization targets are measured spectral data, the starting design is the original theoretical design and the final results gives more actual indices, layer thickness, dispersive index functions and material tooling factors, or some of them by selected optimization for multi-layers. This paper presents some new optimization methods, such as gradually constrained optimization approach, subsection synthesis, accelerating optimization model, etc. The methods applies to all kinds of transmission spectra and do not rely on the existence of interference fringe patterns or transparency. Through a lot of experiments of the films Ta2O5, TiO2 under different ion-assisted deposition (IAD) conditions, the deviation between the measured and the theoretical spectra data is less than 0.52% in p-order model merit function, which shows that these methods are reliable. With "Reverse Engineering" for multi-layers, we have successfully manufactured 400-700nm broadband antireflection coatings (average reflectivity is around 0.25%, maximum reflectivity is on more than 0.35%) and broadband beam splitters (R/T=30:70 for a 45 degree angle of incidence, average reflectivity deviation is less than 2.5% in visible spectral region). Of course, many difficulties have not still been overcome, especially for multi-layers.
Study on preparation technology of GExC1-x film on ZnS substrate
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Inhomogeneous GexC1-xfilm has been prepared by making use of reactive radio frequency magnetron sputtering method. In 8 ~ 12 μm waveband, average transmission rate after film sedimentation on CVD/ZnS single surface is 79.1%, larger than that before filming at 7.8%. As a result of experiments, when ratio of reaction gas flow rate CH4/Ar+CH4changes, refraction ratio of GexC1-x film varies in range of 2.4 ~ 4.1 according to the difference of component X. It makes design of multilayer films and preparation of wide waveband inhomogeneous films very easy. Factors influence transmission rate of GexC1-x film, relationship between refraction ratio of film and ratio of reaction gas flow rate, relationship between film sedimentation speed that corresponds to different refraction ratio and ratio of reaction gas flow rate are analyzed and discussed in this paper.
A new algorithm for integrated image quality measurement based on wavelet transform and human visual system
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An essential determinant of the value of digital images is their quality. Over the past years, there have been many attempts to develop models or metrics for image quality that incorporate elements of human visual sensitivity. However, there is no current standard and objective definition of spectral image quality. This paper proposes a reliable automatic method for objective image quality measurement by wavelet transform and Human visual system. This way the proposed measure differentiates between the random and signal-dependant distortion, which have different effects on human observer. Performance of the proposed quality measure is illustrated by examples involving images with different types of degradation. The technique provides a means to relate the quality of an image to the interpretation and quantification throughout the frequency range, in which the noise level is estimated for quality evaluation. The experimental results of using this method for image quality measurement exhibit good correlation to subjective visual quality assessments.
The spot diagram of waveguide geodesic lens
Zhihua Liu,
Bangren Shi,
Jijiang Wu,
et al.
Show abstract
Geometric Optic analysis method is introduced into GL, two principle surface functions of GL are obtained. And from them, GL can be approximated to a thin lens just like gas lens. With light trail approaching, GL phase transission function can be found. Based on Fresnel diffractive theory, mode distribution of GL is obtained. Our optimal GL of non-curvature singularity and non-spherical has reference numbers: focus 20mm, aperture 8mm transition region
10mm. Incident light wavelength is 0.6328 μm. these parameters are substituted into GL field distribution, Matlab method is used to do analytical solution and intensity distribution. The theory
model is similar to experiments.
Optical test for the primary mirror of a space telescope using a CGH null lens
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MSC (Multi-Spectral Camera) for KOMPSAT2 (Korea Multipurpose Satellite 2) is a Ritchey-Chretien type telescope. Its primary mirror (PM) is a hyperboloidal mirror with 600 mm diameter. To test the PM, we chose a CGH null lens as a null optics. The CGH null lens is much smaller than the Hindle shell, is consist of only one element, and is aligned more easily than the Offner type null lens. The CGH null lens is designed to align and test the aspheric surface at the same time. The CGH lens includes the main part to test the aspheric wavefront from the PM and also includes the alignment part to align the CGH and the PM. The alignment CGH part is consisted of three amplitude type reflection segments to align the CGH and the interferometer, and three phase type transmission segments to align the CGH and the PM. The CGH null lens is made of fused silica by a laser beam writer. We measured the Engineering Model of the PM using this CGH null lens.
Large working area F-Theta lens
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F-Theta lens is different from common photo lenses, and it is usually used in the scanning system to realize linear scanning by means of its linearity. The lens focuses a laser beam and its scanning quality mainly depends on its focusing performance. When the F-Theta lenses used in laser marking systems, as we know, their working area is generally not larger than 300×300mm2 interiorly. In this paper, the design of a kind of F-Theta lens, which has the working area as large as 680mm in diameter, is introduced in detail. Firstly, the first-order optical parameters are determined by its paraxial analysis, flat-field condition, and aberration characteristics. Secondly, the initial structure parameters of the F-Theta lens are obtained through the PW method. And then the optimal F-Theta lens meeting with its required optical performances is gained with some optical design software under practical constrained conditions. The designed system is compact and composed of only four spherical lenses made up of two kinds of common optical glass. Its tube length from the front surface of the first lens to the back surface of the last one is less than 100mm. But the focusing performance of the lens is within diffraction limit on the whole and its distortion relative to the F-Theta linear relation is less than 0.5 percent.
The fluctuation of high-order aberration’s sensitivity in ArF immersion lithography
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To achieve smaller and smaller feature sizes in the semiconductor industry, extreme demands are placed on the lithographic optics, specifically the projection lens. Higher numerical aperture (NA) is adopted to obtain higher resolution. However, higher NA scales the impact of geometrical aberrations on lithography performance. Thus, a detailed understanding of the effect of geometrical aberrations on the lithographic process is indispensable. In this paper, we consider some of the surprising phenomena that occur at such high NA. We discuss the impact of flare, polarization state and MSD on higher-order aberration's sensitivity using ArF immersion lithography to print elbow pattern exposed features in photo resist on 65nm node. The higher-order aberration's sensitivity is analyzed when the annular illumination (NA=1.2, sigma out=0.76, sigma in=0.52) is employed. The 3rd, 5th, 7th, 9th geometrical aberrations according to the Fringe convention are discussed. The sensitivities to individual geometrical aberrations are calculated by introducing a fixed amount of aberration for each Zernike coefficient with all other aberrations being zero. On 65nm node, with annular illumination, the high-order aberration's sensitivity is calculated respectively according to the variation of flare, polarization state, and MSD. The results show that flare, polarization state, and MSD can contribute to the high-order aberration's sensitivity. The aberration sensitivities are increasing with the MSD and flare's value rising. The aberration sensitivities can be decreased when the horizontal linear polarized light is adopted. The merits of adjusting polarization state to choke back the aberration sensitivities are presented.
Tolerance analysis of lenses with high zoom ratio
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Axial and lateral compensators are used for zoom systems tolerancing to improve the manufacturability of high zoom ratio lenses. An investigation into the tolerance distribution for various zoom ratios, and compensation conditions and corresponding performance is presented. A flexible method is applied to a rear focusing four-groups 10X zoom to demonstrate the effectiveness of different compensators.
Interference characteristic analysis on RoF illumination
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The coherent artifacts have harmful influence on the measurement results and make the precision worse during the optical testing. Using RoF illumination method, we can get evener coherent artifacts on the interferogram, improve the gain in S/N ratio, and reduce the measurement error. In this paper we analyze the RoF illumination interferometer, compare the spatial coherence of the RoF and that of the quasi-point light source, get the intensity distribution of the interference field, obtain the fringe visibility, and make a further analysis of the result precision dependence on RoF radius and cavity length.
Measuring the contour of a wavefront using the Irradiance Transport Equation (ITE)
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The Irradiance Transport Equation (ITE), found by Teague, had been used in optics with different applications. One of the field where had been used is in optical testing, for example, with the method developed by Takeda. In this paper following the idea of using different optical and mathematical analysis method, theorical and experimental results are presented.
Numerical analysis of compound aspheric lens design and fabrication
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This paper discussed the scheme of modeling compound aspheric components during the optimization process. First, the method to model the refractive index and thickness changes of the resin layer induced in the injection-mold process is described. It demonstrated the available constraints upon the refractive index difference between the resin and the glass during the optimization run. The tolerance aspects of such components are then investigated, including the refractive index and thickness of the resin layer, as well as the conventional surface roughness, element position and rotation errors, and surface slope errors; especially for the centering tolerance. It is shown that the approximate model might be useful for different combinations with UV-curable resins and glasses for aspheric lens design and fabrication. An objective for optical pickup system comprising one compound aspheric surface is designed with the scheme.
Research iris serial images quality assessment method based on HVS
Zhi-hui Li,
Chang-hai Zhang,
Xing Ming,
et al.
Show abstract
Iris recognition can be widely used in security and customs, and it provides superiority security than other human feature recognition such as fingerprint, face and so on. The iris image quality is crucial to recognition effect. Accordingly reliable image quality assessments are necessary for evaluating iris image quality. However, there haven't uniformly criterion to Image quality assessment. Image quality assessment have Objective and Subjective Evaluation methods, In practice, However Subjective Evaluation method is fussy and doesn't effective on iris recognition. Objective Evaluation method should be used in iris recognition. According to human visual system model (HVS) Multi-scale and selectivity characteristic, it presents a new iris Image quality assessment method. In the paper, ROI is found and wavelet transform zero-crossing is used to find Multi-scale edge, and Multi-scale fusion measure is used to assess iris image quality. In experiment, Objective and Subjective Evaluation methods are used to assess iris images. From the results, the method is effectively to iris image quality assessment.
Study on spherical aberration of imaging system constructed by fractional Fourier transform
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A primary spherical aberration phase factor is introduced for the spherical refracting system and the diffraction integral of the system is obtained. By omitting this primary spherical aberration phase factor, a specific crude imaging system is designed by cascading single spherical refracting fractional Fourier transform units. The spherical aberration of the system are numerically investigated. The relation between fractional Fourier transform and source of spherical aberration of imaging system is discussed.
Design and fabrication of fluorescence fiber gratings
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Rare-earth-element-doped fibers are wildly used in fiber amplifiers, fiber lasers and fiber sensors. Fiber Bragg Gratings (FBGs) are very important optical components in optical communication and sensing. The fluorescence fiber grating consists of fiber amplifiers and fiber gratings. Some fabrication methods of the fluorescence fiber grating are proposed in this paper. After pretreated, for example, Hydrogen loading, the rare-earth-elements-doped fibers become photosensitive fiber. The FBGs can be fabricated along the rare-earth-elements-doped fiber to form the fluorescence fiber gratings. When the pump light goes through the fluorescence fiber grating, the fluorescence light emits as incoherent signal. The power spectrum can be simulated based on an effective analysis method. In experiment, the fluorescence fiber gratings is fabricated to the Erbium doped fiber after Hydrogen loading. The power spectrum of these samples are obtained.
Ronchi test with sub-structured gratings
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The Ronchi test is a well-known method for the testing of optical components and systems, and can be studied by ray tracing and lateral shearing interferometry. In this paper, the Ronchi test is applied using an LCD, for generating gratings with different periods for the dark and light zones, in order to obtain sharpening of the fringes. Experimental and computer simulations will be presented for parabolic surfaces.
Line-contact maching of conic surfaces of revolution and error analysis
Changjun Jiao,
Shengyi Li,
Yifan Dai
Show abstract
A new fabrication technique of conic surface of revolution based on line-contact is presented. The shaping theory is analyzed with geometry method. Conic surfaces can be machined based on this method without complex positioning control. Besides, in this method, one type of surface can be obtained with different tools, inversely, one tool can machine different types of surfaces. Both are got by adjusting the angle α between the normal of the tool surface and the revolution axis of the surface. Error analysis is done under one-order approximation. From these formulas, we can got the idea that the transfer coefficients between the shape error of the machined surface and the positioning error, shape error of the ellipse tool are all smaller than one.
Design and fabrication of C/W hard x-ray supermirrors
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We designed two kinds of supermirrors composed of Carbon and Tungsten in current paper. Using Simplex Optimization method, we designed C/W supermirror with broad incident angular range (0.5°~0.9°) at Cu Kα line (λ=0.154nm). Connecting the analytical method, based on oversimplified analytical and semi-empirical formulas, with the Simplex Optimization method, we designed C/W supermirror with broad photon energy range (16~25keV), at θ=0.5°. The negative effect, due to the interfacial roughness and diffusion between the adjacent sublayers in multilayer, also emerges in simulating the practice performance of the both supermirrors. The supermirrors with broad incident angular range were fabricated by DC magnetron sputtering, because such supermirror is easy to be measured at our lab, using X-ray diffractormeter. The measured reflectivity near the first order Bragg peak is about 30% at Cu Kα line. The roughness factor is about 0.84nm by the fitting data.
New measures of the refractive index in liquids using speckle patterns
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New results obtained with the method to measure the refractive index in liquids by using a speckle pattern are presented.
When a laser beam impinges obliquely on a transparent rectangular cell, its direction of propagation undergoes a lateral shift when the cell is filled with a liquid. The shift depends only on the refractive index of the liquid, on the distance between the parallel walls of the cell and on the incident angle. Similarly, if the cell is illuminated by a speckle pattern, the latter suffers a displacement when the liquid is introduced. A CCD camera records the transmitted speckle pattern before and after filling of the cell with the liquid.
The images are stored in a PC and processed with software to obtain the refractive index. The advantage in determining the displacement through the use of a speckle pattern is that a sub pixel processing can be made of the shifting caused by the liquid. The refractive indices of some liquids were performed, with errors under 1%: acetone, alcohol, water, xylene, butanol, dilution of butanol in xylene and a saturated solution of salt in water.
Design of infrared afocal zoom system
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The design method and result are described for an infrared afocal zoom system. Its zoom ratio is 4, and the corresponding field of view is 3°~12°. The working waveband is from 7.5μm to 10.5μm, and its total length is required to be no more than 350mm. The final optical system consists of 7 elements, with aspheric surfaces and a diffractive optical element. It achieves diffraction-limited imaging at the far infrared waveband. Two conclusions can be drawn from the design. (1) Using diffractive optical elements in the design of an infrared optical system is an effective approach to control color aberrations, which eliminates the need to use exotic and expensive materials and helps to reduce the cost of the system; (2) Functions such as changing the field-of-view, focusing for objects at finite distances and athermalizing the system can be achieved by axially moving a single element in the system.
Usage of a speckle correlation for object surface topography
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The paper demonstrates possibility of application of the method called speckle pattern correlation for topography of the object surface under investigation. Scanning speckle pattern originating from different points of the object surface illuminated with laser beam enables to get information on height profile of the object surface in these points. This is presented on the measurement of the slope of the object surface. The principle of the presented method is shortly described including necessary equations. A possible optical set-up for the measurement of the slope of the object under investigation is designed and acquired results are presented in comparison with theoretic values.
Attempts to encourage secondary students to initiate university studies of physics in the University of Barcelona based on experiments related to optics
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In order to attract the interest for the physical sciences to secondary students to initiate university studies, the Faculty of
Physics of the University of Barcelona has begun a project which consists of the presentation of science in an attractive way by means of carefully chosen demonstrations and experiments and a suitable ambiance of communication. In this paper the details of the organization of the activities, which are based on experiments, mainly related to optics
phenomena.