Wavefront Analysis And Calibration For Computer Generated Holograms
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Wavefront Analysis And Calibration For Computer Generated Holograms
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Author : Wenrui Cai
language : en
Publisher:
Release Date : 2013
Wavefront Analysis And Calibration For Computer Generated Holograms written by Wenrui Cai and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
Interferometry with computer generated holograms (CGH) has evolved to be a standard technology for optical testing and metrology. By controlling the phase of the diffracted light, CGHs are capable of generating reference wavefronts of any desired shape, which allows using of interferometers for measuring complex aspheric surfaces. Fabrication errors in CGHs, however, cause phase errors in the diffracted wavefront, which directly affects the accuracy and validity of the interferometric measurements. Therefore, CGH fabrication errors must be either calibrated or budgeted. This dissertation is a continuation and expansion of the analysis and calibration of the wavefront errors caused by CGH in optical testing. I will focus on two types of error: encoding error and etching variation induced errors. In Topic one, the analysis of wavefront error introduced by encoding the CGH is discussed. The fabrication of CGH by e-beam or laser writing machine specifically requires using polygon segments to approximate the continuously smooth fringe pattern of an ideal CGH. Wavefront phase errors introduced in this process depend on the size of the polygon segments and the shape of the fringes. We propose a method for estimating the wavefront error and its spatial frequency, allowing optimization of the polygon sizes for required measurement accuracy. This method is validated with both computer simulation and direct measurements from an interferometer. In Topics two, we present a new device, the Diffractive Optics Calibrator (DOC), for measuring etching parameters, such as duty-cycle and etching depth, for CGH. The system scans the CGH with a collimated laser beam, and collects the far field diffraction pattern with a CCD array. The relative intensities of the various orders of diffraction are used to fit the phase shift from etching and the duty cycle of the binary pattern. The system is capable of measuring variations that cause 1 nm peak-to-valley (P-V) phase errors. The device will be used primarily for quality control of the CGHs. DOC is also capable of generating an induced phase error map for calibration. Such calibration is essential for measuring freeform aspheric surfaces with 1 nm root-mean-square (RMS) accuracy.
Diffraction Wavefront Analysis Of Computer Generated Holograms
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Author : Yu-Chun Chang
language : en
Publisher:
Release Date : 1999
Diffraction Wavefront Analysis Of Computer Generated Holograms written by Yu-Chun Chang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with categories.
Precision Alignment And Calibration Of Optical Systems Using Computer Generated Holograms
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Author : Laura Elizabeth Coyle
language : en
Publisher:
Release Date : 2014
Precision Alignment And Calibration Of Optical Systems Using Computer Generated Holograms written by Laura Elizabeth Coyle and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
As techniques for manufacturing and metrology advance, optical systems are being designed with more complexity than ever before. Given these prescriptions, alignment and calibration can be a limiting factor in their final performance. Computer generated holograms (CGHs) have several unique properties that make them powerful tools for meeting these demanding tolerances. This work will present three novel methods for alignment and calibration of optical systems using computer generated holograms. Alignment methods using CGHs require that the optical wavefront created by the CGH be related to a mechanical datum to locate it space. An overview of existing methods is provided as background, then two new alignment methods are discussed in detail. In the first method, the CGH contact Ball Alignment Tool (CBAT) is used to align a ball or sphere mounted retroreflector (SMR) to a Fresnel zone plate pattern with micron level accuracy. The ball is bonded directly onto the CGH substrate and provides permanent, accurate registration between the optical wavefront and a mechanical reference to locate the CGH in space. A prototype CBAT was built and used to align and bond an SMR to a CGH. In the second method, CGH references are used to align axi-symmetric optics in four degrees of freedom with low uncertainty and real time feedback. The CGHs create simultaneous 3D optical references where the zero order reflection sets tilt and the first diffracted order sets centration. The flexibility of the CGH design can be used to accommodate a wide variety of optical systems and maximize sensitivity to misalignments. A 2-CGH prototype system was aligned multiplied times and the alignment uncertainty was quantified and compared to an error model. Finally, an enhanced calibration method is presented. It uses multiple perturbed measurements of a master sphere to improve the calibration of CGH-based Fizeau interferometers ultimately measuring aspheric test surfaces. The improvement in the calibration is a function of the interferometer error and the aspheric departure of the desired test surface. This calibration is most effective at reducing coma and trefoil from figure error or misalignments of the interferometer components. The enhanced calibration can reduce overall measurement uncertainty or allow the budgeted error contribution from another source to be increased. A single set of sphere measurements can be used to calculate calibration maps for closely related aspheres, including segmented primary mirrors for telescopes. A parametric model is developed and compared to the simulated calibration of a case study interferometer.
Laser Beam Mode Selection By Computer Generated Holograms
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Author : Victor A. Soifer
language : en
Publisher: CRC Press
Release Date : 1994-07-20
Laser Beam Mode Selection By Computer Generated Holograms written by Victor A. Soifer and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 1994-07-20 with Science categories.
Laser Beam Mode Selection by Computer Generated Holograms brings attention to a new class of optical elements called modans, with applications in laser and fiber optics. Separation of the transverse modes by modans is discussed in close analogy to well-known effects of color separation by diffraction gratings. The book describes the basic questions of digital holography in the recording of complex wavefronts on phase-only media, binary coding cells, multilevel computer-generated holograms, quantization and sampling, image reconstruction, and computer generation of multifocal and multibeam holograms. This collective effort summarizes 12 years of scientific activities in the development of diffractive optical elements and provides considerable material never before published. An interesting appendix dedicates itself to mathematical proof of optimal properties of orthogonal base-functions and eigenfunctions.
Selected Papers On Computer Generated Holograms And Diffractive Optics
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Author : Sing H. Lee
language : en
Publisher:
Release Date : 1992
Selected Papers On Computer Generated Holograms And Diffractive Optics written by Sing H. Lee and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1992 with Computer graphics categories.
An important feature of computer generated holograms (CGHs) is to create wavefronts that may be defined only mathematically. Since A. W. Lohmann and his colleagues invented CGHs in 1966 for spatial filtering in image processing, the applications of CGHs have multiplied to include 3-D display, optical testing, diffractive/binary optics, bifocal intraocular lenses, wavefront transformations for material processing, pickup heads for optical disks, focal plane array detection, coherent laser addition, beam steering, and optical interconnects for parallel computing and neural computing. Today, the applications of CGHs continue to expand. This book features a selection of papers that examine different aspects of the development of CGHs from the 1960s through 1990, because there is no substitute for reading the original papers on any subject, even if that subject is mature enough to have many single-aspect monographs and textbooks. It is hoped that this selection of papers will be valuable additions to many working libraries on this expanding, expansive subject.
Digital Holography And Wavefront Sensing
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Author : Ulf Schnars
language : en
Publisher: Springer
Release Date : 2014-09-19
Digital Holography And Wavefront Sensing written by Ulf Schnars and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-09-19 with Technology & Engineering categories.
This highly practical and self-contained guidebook explains the principles and major applications of digital hologram recording and numerical reconstruction (Digital Holography). A special chapter is designated to digital holographic interferometry with applications in deformation and shape measurement and refractive index determination. Applications in imaging and microscopy are also described. Spcial techniques such as digital light-in-flight holography, holographic endoscopy, information encrypting, comparative holography, and related techniques of speckle metrology are also treated
Use Of Computer Generated Holograms For Optical Alignment
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Author : Rene Zehnder
language : en
Publisher:
Release Date : 2011
Use Of Computer Generated Holograms For Optical Alignment written by Rene Zehnder and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
The necessity to align a multi component null corrector that is used to test the8.4 [m] off axis parabola segments of the primary mirror of the Giant MagellanTelescope (GMT) initiated this work. Computer Generated Holograms (CGHs) areoften a component of these null correctors and their capability to have multiplefunctionality allows them not only to contribute to the measurement wavefront butalso support the alignment. The CGH can also be used as an external tool to supportthe alignment of complex optical systems, although, for the applications shown inthis work, the CGH is always a component of the optical system. In general CGHs change the shape of the illuminating wavefront that then canproduce optical references. The uncertainty of position of those references not onlydepends on the uncertainty of position of the CGH with respect to the illuminatingwavefront but also on the uncertainty on the shape of the illuminating wavefront. A complete analysis of the uncertainty on the position of the projected referencestherefore includes the illuminating optical system, that is typically an interferometer. This work provides the relationships needed to calculate the combined propagationof uncertainties on the projected optical references. This includes a geometricaloptical description how light carries information of position and how diffractionmay alter it. Any optical reference must be transferred to a mechanically tangible quantityfor the alignment. The process to obtain the position of spheres relative to theCGH pattern where, the spheres are attached to the CGH, is provided and appliedto the GMT null corrector. Knowing the location of the spheres relative to theCGH pattern is equivalent to know the location of the spheres with respect to thewavefront the pattern generates. This work provides various tools for the design and analysis to use CGHs foroptical alignment including the statistical foundation that goes with it.
Introduction To Computer Holography
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Author : Kyoji Matsushima
language : en
Publisher: Springer Nature
Release Date : 2020-03-23
Introduction To Computer Holography written by Kyoji Matsushima and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-03-23 with Science categories.
This book covers basic- to expert-level applications in computer holography, a strong candidate for the ultimate 3D display technology. The computer holography developed in the course of the past decade represents the basis of wave optics. Accordingly, the book presents the basic theory of wave optics and practical techniques for handling wave fields by means of the fast Fourier transform. Numerical techniques based on polygons, as well as mask-based techniques, are also presented for calculating the optical fields of virtual 3D models with occlusion processing. The book subsequently describes simulation techniques for very large-scale optical fields, and addresses the basics and concrete applications of simulation, offering a valuable resource for readers who need to employ it in the context of developing optical devices. To aid in comprehension, the main content is complemented by numerous examples of optical fields and photographs of reconstructed 3D images.
Modeling Design And Optimization Of Computer Generated Holograms With Binary Phases
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Author : Jing Wang
language : en
Publisher:
Release Date : 2019
Modeling Design And Optimization Of Computer Generated Holograms With Binary Phases written by Jing Wang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
The computer-generated hologram (CGH) has been demonstrated to play an important role, since its invention by Lohmann in 1960s, in many applications such as wavefront engineering, structured illumination and optical display, etc. In this thesis, the modeling, design and optimization of CGH with binary phases are studied. We considered a practical projection image system with certain working specification, e.g. working distance of 40 cm, depth of field of 10 cm and a diffraction angle of 53 degree for 632 nm working wavelength, and then designed and optimized a binary-phase hologram by direct binary search for this image system. The hologram was fabricated by E-beam lithography. To achieve the required diffraction angle, we discussed the optical architecture in holographic projection image system. The designed CGH and holographic projection image system were validated experimentally by optical reconstruction. Since the pixels will eventually cluster to form polygonal apertures in hologram, which can be seen clearly during the process of direct binary search, we proposed a new approach to directly design polygonal apertures based on triangular layout in CGH of a large number of pixels. The diffraction of aperture was calculated by analytical Abbe transform. The reconstructed image can be expressed as a coherent addition of diffraction patterns from all the straight edges of different orientations and lengths. A two-step optimization including genetic algorithm with local search for encoding binary phases of apertures, followed by direct search for floating covertices of the elementary triangular apertures was developed. We further proposed a quadrilateral aperture layout, which provides more degrees of freedom and can form more diverse polygonal apertures in holograms. The parallel genetic algorithm with local search was adopted to assign binary phases in the first step, and direct search was then used to optimize of locations of covertices of quadrilateral apertures in the second step. Three different schemes for the two-step algorithm were discussed to provide flexible ways to balance the optimization performance and time cost.
Computer Generated Holograms Using 1 D Fourier Transform And A Cylindrical Wavefront Reconstruction
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Author : Antti Saukkonen
language : en
Publisher:
Release Date : 1988
Computer Generated Holograms Using 1 D Fourier Transform And A Cylindrical Wavefront Reconstruction written by Antti Saukkonen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1988 with categories.