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22nd Annual Conference on Novel Optical Systems, Methods, and Applications XXII

作者： Chiu, Po-Sheng Vonmetz, Kurt Canini, Federico Urbach, H. Paul Delft Univ Technol Dept Imaging Phys Lorentzweg 1 NL-2628 CJ Delft Netherlands Datal IP Tech Srl Via San Vitalino 13 I-40012 Calderara Di Reno BO Italy

ISBN: (数字)9781510629042

ISBN: (纸本)9781510629042

Cubic phase wavefront coding technique is applied to an imaging system with the aim of extending the depth of field (DOF). The design is based on the wavefront coding method proposed by Dowski and Cathey(1). The method employs a cubic phase mask (CPM) to modify the point spread function (PSF) of the imaging system under incoherent illumination such that the PSF of the system is formed as an isosceles right triangle, which makes the PSF insensitive to defocus. Researchers have found the optimized values of cubic phase coefficient and the exit pupil distance for the given specifications for solving wavefront coded task-based imaging problem(2). The extended DOF design is usually based on placing a phase mask exactly in the pupil plane of the imaging system. However, this is not always practical because the complex design of the imaging system leads to a limited practical advantage of this kind of arrangement. In this work, the influence of phase mask position upon wavefront coding technique in the doublet imaging system is studied. The main goal is to find the position where to place the CPM in the imaging system, which type of arrangement can effectively improve the modulation transfer function. Finally, we compare two system configurations, front aperture stop and rear aperture stop in designing the doublet wavefront coded system.

关键词： wavefront coding cubic phase mask task-based imaging

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wavefront coded zoom lens with a single moving element

Wavefront coded zoom lens with a single moving element

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Conference on Optical Design and Engineering III

作者： Demenikov, Mads Findlay, Ewan Harvey, Andrew R. Heriot Watt Univ Imaging Concepts Grp Sch Engn & Phys Sci Edinburgh EH14 4AS Midlothian Scotland STMicroelect Edinburgh EH12 7BF Midlothian Scotland

ISBN: (纸本)9780819473301

Traditional zoom lens designs employ multiple moving lens elements to provide simultaneous control of focal length and focal plane. We present an example of a simplified and compact zoom lens design by employing a single moving element to control only the focal length. In this zoom lens, wavefront coding is used to control the defocus. We describe the principles of operation with special attention to image processing. We simulate imaging and image restoration capabilities and present that the zoom lens provides high imaging quality.

关键词： ZOOM lenses wavefront coding extended depth of field optical design design miniaturization design simplification image processing

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Extended-Depth-of-Field Iris Recognition Using Unrestored wavefront-Coded Imagery

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IEEE TRANSACTIONS ON SYSTEMS MAN AND CYBERNETICS PART A-SYSTEMS AND HUMANS 2010年第3期40卷 495-508页

作者： Boddeti, Vishnu Naresh Kumar, B. V. K. Vijaya Carnegie Mellon Univ Dept Elect & Comp Engn Pittsburgh PA 15213 USA

Iris recognition can offer high-accuracy person recognition, particularly when the acquired iris image is well focused. However, in some practical scenarios, user cooperation may not be sufficient to acquire iris images in focus;therefore, iris recognition using camera systems with a large depth of field is very desirable. One approach to achieve extended depth of field is to use a wavefront-coding system as proposed by Dowski and Cathey, which uses a phase modulation mask. The conventional approach when using a camera system with such a phase mask is to restore the raw images acquired from the camera before feeding them into the iris recognition module. In this paper, we investigate the feasibility of skipping the image restoration step with minimal degradation in recognition performance while still increasing the depth of field of the whole system compared to an imaging system without a phase mask. By using a simulated wavefront-coded imagery, we present the results of two different iris recognition algorithms, namely, Daugman's iriscode and correlation-filter-based iris recognition, using more than 1000 iris images taken from the Iris Challenge Evaluation database. We carefully study the effect of an off-the-shelf phase mask on iris segmentation and iris matching, and finally, to better enable the use of unrestored wavefront-coded images, we design a custom phase mask by formulating an optimization problem. Our results suggest that, in exchange for some degradation in recognition performance at the best focus, we can increase the depth of field by a factor of about four ( over a conventional camera system without a phase mask) by carefully designing the phase masks.

关键词： Challenging iris recognition correlation filters extended depth of field wavefront coding

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wavefront coded image restoration algorithm based on compressed sensing for off-axis mirror system 7

Wavefront coded image restoration algorithm based on compres...

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7th Asia Pacific Conference on Optics Manufacture (APCOM)

作者： Yi, Huang Jun, Chang Li Dongmei Cao Jiajing Shan, Du Beijing Inst Technol Beijing 100081 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China Chinese Acad Sci Inst Semicond Beijing 100083 Peoples R China

ISBN: (数字)9781510652095

ISBN: (纸本)9781510652095;9781510652088

By combining optical systems and image processing, wavefront coding can greatly expand the depth of focus and depth of field of optical systems. It has been widely used in iris detection, high-power microscopic objective lens, infrared optical system athermalized, and so on. At present, the image restoration algorithms commonly used in wavefront coding are based on deconvolution, Wiener filtering, and so on. Although these algorithms can achieve an excellent image restoration effect, they will also bring boundary ringing effects and artifacts to the image. When the image is disturbed by strong noise, the restoration effect will also be seriously affected. To solve these problems, a wavefront coded image restoration algorithm based on compressed sensing is proposed in this paper. The strong data reconstruction ability of the compressed sensing restoration algorithm is used to restore the encoded image obtained by the wavefront coding system. This method can effectively suppress noise and reconstruct the image without artifact and boundary ringing effect. Through the comparison of simulation results, the effectiveness of the proposed method is verified.

关键词： wavefront coding compressed sensing artifact

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Noise as a Design Constraint in Broadband wavefront Coded Optical Systems

Noise as a Design Constraint in Broadband Wavefront Coded Op...

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International Optical Design Conference (IODC)

作者： Adelsberger, Kathleen Boye, Robert Zavislan, James Univ Rochester 275 Hutchinson Rd Rochester NY 14627 USA Sandia Natl Labs Albuquerque NM 87123 USA

Simulated results demonstrate the impact of detector noise on the design of a broadband wavefront coded optical system. We conclude that noise must be included as a first-order design constraint in cubic phase-encoded... 详细信息

ISBN: (纸本)9781628413786

关键词： wavefront coding Noise Lens design Cubic phase Extended depth of focus Optimization

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Implementation of a wavefront coded microscope by the use of a spatial light modulator 19

Implementation of a Wavefront coded microscope by the use of...

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19th Conference on Current Developments in Lens Design and Optical Engineering

作者： Ortega-Sanchez, K. Toxqui-Quitl, C. Padilla-Vivanco, A. Univ Politecn Tulancingo Ingn 100 Tulancingo 43629 Hidalgo Mexico

ISBN: (数字)9781510620629

ISBN: (纸本)9781510620629

wavefront coding (WFC) technique is typically used to compensate for optical aberrations related to defocus. An advantage of WFC are that the depth of field (DOF) will be increased and the weight and size of an optical system are reduced. In this work a WFC system is analyzed to extend the DOF of the microscope objective. The Point Spread Function (PSF) is used to modify in such a way that it is invariant to defocus in a range of axial distances. A liquid crystal display light modulator (LC SLM) in a 4f imaging system is used for the implementation of the phase masks (PM). LC SLM screens modulate both the amplitude and the phase of the input beam. This display allows a flexible implementation of different profiles of phase masks that are generated from different families of functions, this is because the parameters can be dynamically modified. In this document, we propose an experimental setup for extended DOF in optical microscopy. Experimental results are presented using a LC - SLM.

关键词： wavefront coding Phase Mask Microscope system LC-SLM

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Optimized restoration of wavefront coded images 15

Optimized restoration of wavefront coded images

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Conference on Current Developments in Lens Design and Optical Engineering XV

作者： Toxqui-Quitl, C. Acosta, Eva Arines, Justo Padilla-Vivanco, A. Univ Politecn Tulancingo Ingn 100 Tulancingo 43629 Hidalgo Mexico Univ Santiago de Compostela Dept Fis Aplicada Santiago De Compostela 15782 Spain

ISBN: (纸本)9781628412192

wavefront coding (WFC) uses a special aspheric optics and digital image processing to extend the depth of focus in imaging systems. An intermediate blurred image is generated by the spatial convolution of the image with the point spread function (PSF) of a cubic phase mask. Restoration tests are performed on an optically encoded image. The best option to restore an image is not always given by a deconvolution method using the PSF of the imaging system. Due to it is limited by the perfect PSF of the system. In this study, the restored image is given by a deconvolution method using the numerical PSF. As the quality of the image is depended of the pupil diameter and strength of the wfc phase plate, an optimization was achieved by means of measuring the decoded image contrast. Results shows a high resolution decoded image.

关键词： image restoration wavefront coding genetic algorithms focus invariant

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Implementation of a wavefront coded imaging system using a spatial light modulator

Implementation of a wavefront coded imaging system using a s...

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Conference on Optical Design and Engineering III

作者： Carles, Guillem Muyo, Gonzalo Bosch, Salvador Harvey, Andrew R. Univ Barcelona Dept Appl Phys & Opt Diagonal 647 Barcelona Spain Heriot Watt Univ Sch Engn & Appl Sci Edinburgh EH14 4AS Midlothian Scotland

ISBN: (纸本)9780819473301

We present the results of the utilization of a Spatial Light Modulator Liquid Crystal Display for the implementation of wavefront codification procedures in all imaging system. The light modulator works in transmission mode at the pupil of the instrument. The main disadvantage is that the procedure implies a calibration of the device as well as an inherent image processing. The more interesting feature we can obtain is the versatility related to the use of all electronic device at the pupil, as compared with conventional (fixed) manufactured ones.

关键词： wavefront coding Image processing Vision systems

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The design of wavefront coded imaging system

The design of wavefront coded imaging system

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International Symposium on Advanced Optical Design and Manufacturing Technologies / International Symposium on Astronomical Telescope and Instrumentation

作者： Lan, Shun Cen, Zhaofeng Li, Xiaotong Zhejiang Univ State Key Lab Modern Opt Instrumentat Hangzhou 310027 Peoples R China

ISBN: (数字)9781510607675

ISBN: (纸本)9781510607675

wavefront coding is a new method to extend the depth of field, which combines optical design and signal processing together. By using optical design software ZEMAX, we designed a practical wavefront coded imaging system based on a conventional Cooke triplet system. Unlike conventional optical system, the wavefront of this new system is modulated by a specially designed phase mask, which makes the point spread function (PSF) of optical system not sensitive to defocus. Therefore, a series of same blurred images obtained at the image plane. In addition, the optical transfer function (OTF) of the wavefront coded imaging system is independent of focus, which is nearly constant with misfocus and has no regions of zeros. All object information can be completely recovered through digital filtering at different defocus positions. The focus invariance of MTF is selected as merit function in this design. And the coefficients of phase mask are set as optimization goals. Compared to conventional optical system, wavefront coded imaging system obtains better quality images under different object distances. Some deficiencies appear in the restored images due to the influence of digital filtering algorithm, which are also analyzed in this paper. The depth of field of the designed wavefront coded imaging system is about 28 times larger than initial optical system, while keeping higher optical power and resolution at the image plane.

关键词： wavefront coding extended depth of field cubic phase mask

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Restoring wavefront coded iris image through the optical parameter and regularization filter

Restoring wavefront coded iris image through the optical par...

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International Conference on Optical Instruments and Technology (OIT) - Optoelectronic Imaging and Processing Technology

作者： Li Yingjiao He Yuqing Feng Guangqin Hou Yushi Liu Yong Beijing Inst Technol Sch Optoelect Minist Educ China Key Lab Photoelect Imaging Technol & Syst Beijing 100081 Peoples R China

ISBN: (纸本)9780819488411

wavefront coding technology can extend the depth of field of the iris imaging system, but the iris image obtained through the system is coded and blurred and can't be used for the recognition algorithm directly. The paper presents a fuzzy iris image restoration method used in the wavefront coding system. After the restoration, the images can be used for the following processing. Firstly, the wavefront coded imaging system is simulated and the optical parameter is analyzed, through the simulation we can get the system's point spread function (PSF). Secondly, using the blurred iris image and PSF to do a blind restoration to estimate a appropriate PSFe. Finally, based on the return value PSFe of PSF, applying the regularization filter on the blurred image. Experimental results show that the proposed method is simple and has fast processing speed. Compared with the traditional restoration algorithms of Wiener filtering and Lucy-Richardson filtering, the recovery image that got through the regularization filtering is the most similar with the original iris image.

关键词： Iris recognition wavefront coding Image restoration Regularization filter

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