The aero-optical aberration of conformal dome (AOACD) is difficult to correct and would cause serious image degradation. wavefront coding (WFC) image technique includes the optics and the digital processing steps to a...
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The aero-optical aberration of conformal dome (AOACD) is difficult to correct and would cause serious image degradation. wavefront coding (WFC) image technique includes the optics and the digital processing steps to achieve the final high-quality images and it can be used to control the optical aberrations. In this paper, a strategy for correcting the AOACD is presented based on WFC technology. The thermal-structure simulation results of the conformal dome are obtained by using ANSYS. The performance degradation of the conformal optical system affected by aero-optical effect is analyzed by using CODEV. Then, a typical generalized cubic phase mask is inserted into the pupil plane of the conformal optical system to suppress its aero-optical aberration. The simulation results show that (1) the image degradation is mainly caused by the refractive index distribution of the conformal dome rather than its deformation;(2) the utilization of WFC technology could suppress AOACD effectively. This work is of consequence in conformal optics and aero-optics.
wavefront coding technology can extend the depth of focus of a well-corrected three-mirror anastigmatic optical system by about ten times, but the image obtained directly by charge-coupled devices blurs at the same ti...
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wavefront coding technology can extend the depth of focus of a well-corrected three-mirror anastigmatic optical system by about ten times, but the image obtained directly by charge-coupled devices blurs at the same time. An effective image restoration must be applied to these blurred images. This paper describes an innovative method that restores the blurred image, which combines the optical design software and mathematical software. The point spread function of system with wavefront coding technology is quite different from the usual and difficult to simulate by a disk function or other simple function in most cases. The commercial optical design software is applied to obtain the point spread function. If a 1 X 1-pixel image with brightness 255 is set as the point source of a optical system, the result of calculation software using a ray tracing algorithm will itself be the digital point spread function. This is proven to be a simple and effective way to acquire the complicated point spread functions of unusual optical systems such as those using wavefront coding technology. A regularization factor and contrast-adjusting factors are introduced into the classical Wiener filter, which achieves good restored images: the root-mean-square error is less than 0.0193, while the peak signal-noise ratio is higher than 23.7. Some parameters of the filter can be adjusted so that the restored image is more suitable for evaluation by eye. It is also shown that a single filter can restore all the images within the extended depth of focus. (C) 2008 Society of Photo-Optical Instrumentation Engineers.
Because of obvious drawbacks including serious artefacts and noise in a decoded image, the existing wavefront coding infrared imaging systems are seriously restricted in application. The proposed ultra-precision diamo...
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Because of obvious drawbacks including serious artefacts and noise in a decoded image, the existing wavefront coding infrared imaging systems are seriously restricted in application. The proposed ultra-precision diamond machining technique manufactures an optical phase mask with a form manufacturing errors of approximately 770 nm and a surface roughness value Ra of 5.44 nm. The proposed decoding method outperforms the classical Wiener filtering method in three indices of mean square errors, mean structural similarity index and noise equivalent temperature difference. Based on the results mentioned above and a basic principle of wavefront coding technique, this paper further develops a wavefront coding infrared imaging system. Experimental results prove that our wavefront coding infrared imaging system yields a decoded image with good quality over a temperature range from -40 degrees C to + 70 degrees C.
The refractive index of the lenses used in optical designs varies with wavelength, causing light rays to fail when focusing on a single plane. This phenomenon is known as chromatic aberration (CA), chromatic distortio...
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The refractive index of the lenses used in optical designs varies with wavelength, causing light rays to fail when focusing on a single plane. This phenomenon is known as chromatic aberration (CA), chromatic distortion, or color fringing, among other terms. Images affected by CA display colored halos and experience a loss of resolution. Fully achromatic systems can be achieved through complex and costly lens designs and/or computationally when digital sensors capture the image. In this work, we propose using the wavefront coding (WFC) technique with a trefoil-shaped phase modulation plate in the optical system to effectively increase the resolution of images affected by longitudinal chromatic aberration (LCA), significantly simplifying the optical design and reducing costs. Experimental results with three LEDs simulating RGB images verify that WFC with trefoil phase plates effectively corrects longitudinal chromatic aberration. Transverse chromatic aberration (TCA) is corrected computationally. Furthermore, we demonstrate that the optical system maintains depth of focus (DoF) for color images.
wavefront coding is a technology which combination of the optical design and digital image processing. By inserting a phase mask closed to the pupil plane of the optical system, the wavefront of the system is re-modul...
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ISBN:
(纸本)9781510610132;9781510610149
wavefront coding is a technology which combination of the optical design and digital image processing. By inserting a phase mask closed to the pupil plane of the optical system, the wavefront of the system is re-modulated. And the depth of focus is extended consequently. In reality the idea is same as the athermalization theory of infrared optical system. In this paper, an uncooled infrared dual field optical system with effective focal as 38mm/19mm, F number as 1.2 of both focal length, operating wavelength varying from 8 mu m to 12 mu m was designed. A cubic phase mask was used at the pupil plane to re-modulate the wavefront. Then the performance of the infrared system was simulated with CODEV as the environment temperature varying from -40 C-omicron to 60 C-omicron. MTF curve of the optical system with phase mask are compared with the outcome before using phase mask. The result show that wavefront coding technology can make the system not sensitive to thermal defocus, and then realize the athermal design of the infrared optical system.
wavefront-coding imaging can achieve high-quality imaging along with a wide range of defocus. In this paper, the anti-laser detection and damage performance of wavefront-coding imaging systems using different asymmetr...
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wavefront-coding imaging can achieve high-quality imaging along with a wide range of defocus. In this paper, the anti-laser detection and damage performance of wavefront-coding imaging systems using different asymmetric phase masks are studied, through modeling and simulation. Based on FresnelKirchhoff diffraction theory, the laser-propagation model of the wavefront-coding imaging system is established. The model uses defocus distance rather than wave aberration to characterize the degree of defocus of an imaging system. Then, based on a given defocus range, an optimization method based on Fisher information is used to determine the optimal phase-mask parameters. Finally, the anti-laser detection and damage performance of asymmetric phase masks at different defocus distances and propagation distances are simulated and analyzed. When studying the influence of defocus distance, compared to conventional imaging, the maximum single-pixel receiving power and echo-detection receiving power of asymmetric phase masks are reduced by about one and two orders of magnitude respectively. When exploring the influence of propagation distance, the maximum single-pixel receiving power of asymmetric phase masks decreases by about one order of magnitude and remains stable, and the echodetection receiving power gradually decreases with increasing propagation distance, until it approaches zero.
A simple graphical interpretation at the pupil of an optical system is proposed to analyse the properties of the cubic-phase wavefront-coding function. The approach explains the invariance achieved against optical def...
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A simple graphical interpretation at the pupil of an optical system is proposed to analyse the properties of the cubic-phase wavefront-coding function. The approach explains the invariance achieved against optical defocus of wavefront coding imaging systems with simplicity and clarity. Next, an analytical approximation of the modulation-transfer function of general wavefront coding systems is derived and used, in combination with the graphical interpretation, for selecting the optimal strength of the cubic-phase encoding function. (C) 2012 Elsevier Ltd. All rights reserved.
wavefront coding is a technology which combination of the optical design and digital image *** inserting a phase mask closed to the pupil plane of the optical system,the wavefront of the system is *** the depth of foc...
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wavefront coding is a technology which combination of the optical design and digital image *** inserting a phase mask closed to the pupil plane of the optical system,the wavefront of the system is *** the depth of focus is extended *** reality the idea is same as the athermalization theory of infrared optical *** this paper,an uncooled infrared dual field optical system with effective focal as 38mm/19 mm,F number as 1.2 of both focal length,operating wavelength varying from 8μm to 12μm was designed.A cubic phase mask was used at the pupil plane to re-modulate the *** the performance of the infrared system was simulated with CODEV as the environment temperature varying from-40 D to 60 *** curve of the optical system with phase mask are compared with the outcome before using phase *** result show that wavefront coding technology can make the system not sensitive to thermal defocus,and then realize the athermal design of the infrared optical system.
wavefront coding technique has been used widely to extend the depth of field of optical systems since it was proposed by Dowski and Cathey in ***,it belongs to computational imaging which
ISBN:
(纸本)9781510607682
wavefront coding technique has been used widely to extend the depth of field of optical systems since it was proposed by Dowski and Cathey in ***,it belongs to computational imaging which
The phase mask plays a key role in wavefront coding *** order to find the phase coding device with better performance,a new kind of phase mask-five times phase mask is proposed,based on cubic phase mask in common use,...
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The phase mask plays a key role in wavefront coding *** order to find the phase coding device with better performance,a new kind of phase mask-five times phase mask is proposed,based on cubic phase mask in common use, and its coding properties are studied in the *** of all,the reason of depressing spherical aberration is analyzed by deriving the asymptotic solution to OTF of the wavefront coding systems with five times phase *** then we compare the effects of inhibition of spherical aberration when place the cubic and five times phase mask respectively. Finally,the experimental simulation is *** results show that on the specific threshold(MTF=0.1)the normalized bandwidth of the system with five times phase mask can be reached 3 times of that with the cubic one;at the same characteristic frequency(h=0.5),the MTF value is 2 times of that in system with cubic *** the MTF consistency in the low frequency region and the PTF consistency in the high frequency region of the system with a five times phase mask are better than those with a cubic one in condition of different spherical *** with the cubic phase mask,the five times phase mask performs better in inhibition of spherical aberration.
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