Laser has several advantages, such as high brightness, excellent directivity, good monochromatic, good coherence and so on . Therefore, in ranging schemes which combine laser sensor technology and automatic control technology , the laser ranging is most commonly used nowadays . First, we introduce the principle of grating diffraction in this paper, and proposes a method for ranging based on the laser reflection characteristics of target. Let the laser beam reflected from the target through the diffraction grating and lens and image on the CCD. In the horizontal plane perpendicular to the direction of incidence, grating, lens and CCD make up of an imaging device, and which can measure the distance of target for many times by moving itself horizontally. We can calculate the distance through measuring the range between the central point of the CCD and zero diffraction fringe. Then, we analyze the influence from the targets’ scattering characteristics. Lastly, we simulate the different status according to the proportion of mirror reflection of the actual targets’ scattering characteristics and get a conclusion that only the proportion of mirror reflection exceeds a particular ratio can calculate a valid distance.
Proc. SPIE. 9685, 8th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems; and Smart Structures and Materials
KEYWORDS: Lithography, Diffraction, Monochromatic aberrations, Error analysis, Distortion, Lens design, Monte Carlo methods, Image quality, Modulation transfer functions, Tolerancing
Because industry demand for LED,LCD panel continues to increase, the high yield of micron-scale resolution lithography is increasingly prominent for manufacturers, which requires the field of lithography objective lens becomes larger. This paper designed a lithography lens with large field, whose effective image side field will reach to 132 × 132mm.Subsequently, the tolerance was analysed by simulation for the optical system. Finally, it is proved that the design meets the requirements of micron-scale resolution.
A hybrid algorithm based on the simulated annealing algorithm and the iterative algorithm is proposed for the design of diffractive optical element (DOE) to shape the laser beams. The algorithm has the global optimization ability of simulated annealing algorithm as well as the local optimization ability of iterative algorithm. Comparisons between the hybrid algorithm and other two optimization algorithms show that the hybrid algorithm has satisfactory convergence property and design accuracy. Numerical simulation results demonstrate that the diffraction efficiency of the DOE is higher than 94% and non-uniformity is less than 1%. Therefore, this algorithm can be well applied in the field of beam shaping.
For novel cooled 640×512 large focal plane array staring focal plane array (FPA) infrared detector with the picture clement size of 15 μm×15 μm,a mid-wave infrared step-zoom detection imaging system with a large FPA was presented in the paper.The manner of variational fov was accomplished by switching two lenses into the narrow fov system layout with mechanism framework.The parameters of the novel system are 4.0 f/number, 800mm/400mm effective focal length (EFL) and 3.7-4.8 μm spectrum region，100% cold shield efficiency.Image quality and thermal Analysis was evaluated by Code-v optical design software.At the spatial frequency 33lp/mm,the Modulation Transfer Function(MTF) was above 0.15 both the long EFL and short EFL in the working temperature range -35°C～55°C.
With the increase of the numerical aperture (NA), the polarization of light affects the imaging quality of projection lens more significantly. On the contrary, according to the mask pattern, the resolution of projection lens can be improved by using the polarized illumination. That is to say, using the corresponding polarized beam (or polarization-mode) along with the off-axis illumination will improve the resolution and the imaging quality of the of projection lens. Therefore, the research on the generation of various polarization modes and its conversion methods become more and more important. In order to realize various polarization modes in polarized illumination system, after read a lot of references, we provide a way that fitting for the illumination system with the wavelength of 193nm.Six polarization-modes and a depolarized mode are probably considered. Wave-plate stack is used to generate linearly polarization-mode, which have a higher degree polarization. In order to generate X-Y and Y-X polarization mode, the equipment consisting of four sectors of λ/2 wave plate was used. We combined 16 sectors of λ/2 wave plate which have different orientations of the “slow” axis to generate radial and azimuthal polarization. Finally, a multi-polarization control device was designed. Using the kind of multi-polarization control device which applying this method could help to choose the polarization modes conveniently and flexibility for the illumination system.
To overcome the accuracy limitation due to the aberration of reference wavefront in the interferometer testing, the point diffraction interferometer (PDI) uses the pinhole to create an ideal diffraction sphere wavefront as the reference wavefront. Because the perfect pinhole is hard to manufacture, then the imperfect pinhole will cause the wavefront errors which will influence the test accuracy. In this paper we use the absolute testing method to test the wave front of the pinhole. Then the testing accuracy of point diffraction interferometer can be improved by subtracting the error of the pinhole. In this paper a Phase-shifting point diffraction interferometer system is designed to testing the pinhole. We use three pinholes to test each other. According the algorithm of the absolute testing method, we can calculate the wavefront error of the pinhole. Then the testing accuracy of point diffraction interferometer can be improved by subtracting the error of the pinhole.
Proc. SPIE. 8418, 6th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Smart Structures, Micro- and Nano-Optical Devices, and Systems
A design method of diffractive optical element is presented for converting a single modal Gaussian beam into a flat-top
beam in the far field of the source. The design is based on geometrical method and modified Gerchberg-Saxton method.
Geometrical method derives from the conservation of energy and the constant optical path length. This method could
supply initial phase distribution of the modified Gerchberg-Saxton method. To find the optimization design results, the
modified Gerchberg-Saxton method is important to choose the feedback factor to increase the convergent speed. In
addition, tolerances and limitations of such elements result in a reduction of the diffraction efficiency and as a result of
stray light. Further study indicates that deviation of the laser wavelength, incident beam, and observation plane can
greatly influence flat-top beam shaping quality. On the basis of theoretical and experimental results, limitations for the
application of diffractive beam shaping elements are investigated.
In order to eliminate the measurement errors caused by the instability of laser beams, a real-time compensation algorithms for the random drifts of laser beams based on moving average (MA) correction mechanism was presented. By establishing a correction model with two fast steering mirrors in the beam delivery path and analyzing the pulse to pulse beam fluctuation, a real-time beam drifts correction is implemented based on closed loop feedback control, which especially focuses on reducing the pulse to pulse drifts and ground fluctuations. The simulation results show that this algorithm can control beam drifts effectively. Optimal MA can be reduced to 3n<sup>-1/2</sup> times (n--pulse numbers in a window) without the ground vibrations. There are a series of improvements on the moving standard deviation (MSD) as well. MSD get a sudden decline at the window pulse. Meanwhile, the drifts can be restrained while loading the ground vibrations without any big jump, and the dropping amplitude is bigger than without the ground vibration. MSD drop while the whole system is controlled by this compensation method and the results are stable. The key of this compensation method for random drifts of laser beams based on moving average feedback control lies in the appropriate corrections formula. What is more, this algorithm which is practical can achieve high precision control of direction drifts.
Result of the testing contain the reference surface errors and test surface errors in the high-accuracy Phase shifting
interferometer which test the relative phase between the two surface. The test accuracy can be achieved by removing the
error of reference surface. In this case, one of body of so-called absolute testing must be used which can test the
systematic errors, including the reference surface, of the instrument to be used to improve the test accuracy. The
accuracy of the interferometer needs different methods to determine in the high accuracy testing. Even-Odd function
method and rotation shear method is introduced in this paper. We use the Zygo interferometer Verifire Asphere to do the
experiment and analyze the errors caused by data processing and interpolation. The result of the experiment can
determine the accuracy of our arithmetic.
The structure combining the microlens and DOE is not sensitive to the incident beam and can control the overall shape
profile flexibly. So that the structure called DOE array is designed in this paper in order to shape the unstable laser beam
to the four polar uniformity distribution. The paper gives the principle of the DOE array and the design process. The
array element determines the profile of the output beam. It is designed using the G-S algorithm and the Adaptive
Addition algorithm (A-A). The number of the DOEs is optimized and analyzed. The simulative diffraction efficiencies
are 89% and non-uniformities are less than 3% when the incident beams are Gaussian, supper-Gaussian, paraboloid and
random distributions. In experiment, diffraction efficiency of 77% and maximum non-uniformity of 5.6% are got on the
condition of the different input laser beam. So the effect on the instability of the incident beam could be decreased.
Recently most of modern absolute measurement rotation the flats or spheres in the interferometer. We review traditional
absolute testing of flats methods and emphasize the method of even and odd functions. The rotation of the lens can lead
to some errors such as angle rotation error, center excursion error and other coordinate system motion error. We analyze
the errors by using Zernike polynomial. The flat or sphere can be expressed as Zernike polynomial which can also be
divided into even-odd, odd-even, even-even and odd-odd functions. We can use 36 Zernike polynomials to generate 3
plats A, B, C. Then the six measurements can be generated from the three plats. For the angle rotation error, we can
simulate the angle error distribution and substitute in the systems. According the error distribution we can change the
arithmetic to improve the measurement accuracy. The results of errors analyzed by means of Matlab are shown that we
can change the arithmetic according the coordinate direction motion errors which can be detected to improve the accuracy. The analysis results can also be used in other interferometer systems which have the motion of the coordinate system.
Diffractive optical elements (DOEs) are more flexible and powerful than tradition refractive-reflective optical
elements in correcting chromatic aberration of an optical system. In this paper the principle of correcting
secondary spectrum is described. In order to compare the effect of DOEs on correcting secondary spectrum, we
use CODE V to design a refractive telephoto system with different strategies: (I) All surfaces are spherical; (II)
One surface is diffractive in the system; (III) Two or more surfaces are diffractive (Multi-layer diffractive
system). It is found that multi-layer diffractive elements used in a telephoto system can easily correct
secondary spectrum without high dispersion glasses, such as calcium fluoride, at the same time high diffraction
efficiency and broad spectral bandwidth can be obtained. And the most important of all, the length of the
telephoto system can be shortened by about 30%, and the weight can be greatly cut.
The use of lasers in a projection display enables the creation of vibrant images with extensive color coverage. By
adding a phase modulators in illumination systems and keeping the most part structures of the classic projection,
speckle on the screen and retinas of the observers were restrained. The speckle's form and restraining were
simulated. It was obtained form simulations that the contrasts of residual speckle on screen and on retinas are
0.0107 and 0.0132. The simulation proves that speckle on screen and on retinas can be suppressed by phase
modulation of the illumination light in projection. It also indicated that the numerical aperture of projector affect
the residual speckle on retinas. Experiments of speckle restraining were performed. It confirmed the results of the
We present the lithography scheme that use high-numerical-aperture photon sieves array as focusing elements in a
scanning X-ray maskless nanolithography system. The system operating at wavelength of 0.5~2nm synchrotron light
sources radiated, each of a large array of photon sieves focuses incident X-ray into a diffraction-limited on-axis
nanoscale spot on the substrate coated photoresist. The X-ray intensity of each spot is modulated by means of a spatial
light modulator. Patterns of arbitrary geometry are exposed and written in a dot matrix fashion while the substrate on a
stepping stage is precisely driven in two dimensions according to the computer program. The characteristics of
synchrotron radiation light, resolution limits and depth of focus of the lithographic system are discussed. The design and
fabrication of photon sieve are illustrated with a low-numerical-aperture amplitude-photon sieve fabricated on a chrome-coated
quarts plate by means of laser-beam lithographic process, which minimum size of pinhole was 5.6um. The
focusing performance of the photon sieve operating at wavelength of 632.8nm was simulated and tested.
The weight of the optical elements of a system used in the aviation and aerospace industry must be as light as possible, on condition that the imaging performance of the system satisfies user’s demand. However, optical elements will deform easily under internal or external pressure if it becomes thinner, and then influences the imaging performance of the whole optical system. In this paper, the main mirror of the Cassegrain system is studied with finite-element analysis (FEA) to predict its surface deformation through simulating its working conditions. The surface deformation is also tested and analyzed after machining and mounting. The obtained interferometric data, Zernike coefficients, is written into CODE V, an excellent software for designing optical systems, to analyze the imaging performance of the designed optical system. Through analyzing the deformation of the metal mirror it can be found that the maxima RMS change of the whole optical system is 0.0059λ, which is only 1.52 percent of the designed value. In the full field of view, the RMS error is less than 0.07λ, that means the imaging performance of the whole optical system is close to the diffraction limit.
Polarization effects have only recently been considered an issue that is growing more for optical lithography. It has been demonstrated that wire-grid structures placed within features have the ability to polarize incident light on a mask. This paper also recognizes the advantages that can be gleamed from the polarization properties, but differs in that it attempts to use a chromium wire-grid polarization mask itself to polarize the incident light. In this paper, we explore a vector model of microlithography imaging with polarization distribution function. Polarization from chromium wire-grid polarization mask can be used as a new lever to improve lithographic performance. This paper also addresses the fundamental issues underlying the design of such a chromium wire-grid polarization mask. The influence of a chromium wire-grid polarization mask on microlithography system has been systematically investigated by comparison on the imaging contrast and the process window. We compare the effects of polarization light imaging with a conventional mask and a chromium wire-grid polarization mask at wavelength of 0.248 μm, a numerical aperture of 0.65 and a partial-coherence of 0.2. It can be concluded that a high-resolution imaging performance can be obtained by using chromium wire-grid polarization mask.
Diagnostic techniques based on optical spectroscopy have the potential to link the biochemical and morphological properties of tissues. Light-induced fluorescence (LIF) spectroscopy as a noninvasive “optical biopsy” method has been widely used to detect small lesions <i>in vivo</i>. Confocal fluorescence spectroscopy provides a tool for optical sectioning of tissue and provides an approach for identifying small shifts in the emission spectra that are caused by intracellular microenvironment factors. The ability to demarcate abnormal and normal tissue with a confocal spectroscopy system depends on the ability of interpreting the source of fluorescence within the samples. It is realized by spatially dispersing the fluorescence collected with a fiber that serves as the pinhole aperture of the confocal system. In order to tracing the autofluorescence spectral signals of tissue layer by layer, a confocal fluorescent spectroscopy system has been set-up. Experiments have been carried out with fluorescent phantom and animal models. With an axial resolution of 10um in animal tissues, this confocal spectral system observed the spectral differences in spectral shape and spectral peak position among different layers of tissue illuminated with 349nm laser. It was also found that the fluorescence intensity is depth-dependent. In conclusion, confocal fluorescence spectroscopy can provide more diagnostic information due to its ability of optical sectioning. It’s hopeful that a confocal spectral system can detect cancer at much earlier stage.
The influence of polarization on the image performance of optical lithography systems has been systematically investigated through comparing the image contrast and the process window with TE-polarization, TM-polarization and un-polarized light, respectively. The simulation results show that the TE-polarization imaging is possible to improve the image performance of optical lithography systems, especially for those systems with high numerical aperture. The effects of polarized-light imaging with a conventional masks and a polarized film mask were studied by carrying out series of experiments under the conditions: 436nm exposure wavelength, numerical aperture of 0.5 and partial-coherence factor of 0.2. It is found that the image quality of the L&S patterns with the polarized film mask is better than that of with the conventional mask and, 0.3 <i>μm</i> L&S patterns are obtained with the polarized film mask.