• Transactions of the Society of Information Storage Systems
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• v.5 no.1
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• pp.36-40
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• 2009

We describe the experimental realization of image system using wavefront coding in 3-Mega pixel mobile phone camera. We designed aspheric lens to extend the depth of field (DOF) using wavefront coding. In addition, through the aspheric lens and lens barrel manufacturing, we obtained a raw image from a camera module. In our method, the acquired images are restored in the spatial frequency domain using the proposed filter and the spatial frequency response (SFR) is calculated. The proposed filters are composed of image denoising filter using low band pass filter in frequency domain and restoration filter for image restoration. Finally, we achieve an enhanced image by super-resolution image processing. Visual examples are given to demonstrate the performance of the proposed filter.

• Current Optics and Photonics
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• v.7 no.1
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• pp.1-14
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• 2023

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.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2899-2908
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• 2021

The laser transport system of the high power laser facility is mainly composed of large-aperture laser transport mirrors (TMs). Obtaining the high-resolution online damage images during the operation, which is of great significance for operating safely of the mirrors and the facility. Based on wavefront coding, pan-tilt scanning and image stitching technologies, an online laser-damage images detection system is designed, and it can achieve high-precision detection of surface characteristics of large-aperture laser transport mirrors. The preliminary simulation proves that the system can solve the depth of field matching problem caused by pan-tilt tilt imaging and achieve higher resolution.

• Journal of Broadcast Engineering
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• v.22 no.3
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• pp.401-404
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• 2017

The 360 VR video has a format of a stereoscopic shape such as an isometric shape or a cubic shape or a cubic shape. Although these formats have different characteristics, they have in common that the resolution is higher than that of a normal 2D video. Therefore, it takes much longer time to perform coding/decoding on 360 VR video than 2D Video, so parallel processing techniques are essential when it comes to coding 360 VR video. HEVC, the state of art 2D video codec, uses Wavefront Parallel Processing (WPP) technology as a standard for parallelization. This technique is optimized for 2D videos and does not show optimal performance when used in 3D videos. Therefore, a suitable method for WPP is required for 3D video. In this paper, we propose WPP coding/decoding method which improves WPP performance on cube map format 3D video. The experiment was applied to the HEVC reference software HM 12.0. The experimental results show that there is no significant loss of PSNR compared with the existing WPP, and the coding complexity of 15% to 20% is further reduced. The proposed method is expected to be included in the future 3D VR video codecs.

• Journal of the Optical Society of Korea
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• v.19 no.5
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• pp.487-493
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• 2015

A wavefront coding (WFC) technique provides an extension of the depth of field for a microscopy imaging system with slight loss of image spatial resolution. Through the analysis of the relationship between the incidence angle of light at the phase mask and the system pupil function, a mixing symmetrical cubic phase mask (CPM) applied to 5X-40X micro-objectives is optimized simultaneously based on point-spread function (PSF) invariance and nonzero mean values of the modulation transfer function (MTF) near the spatial cut-off frequency. Optimization results of the CPM show that the depth of field of these micro-objectives is extended 3-10 times respectively while keeping their resolution. Further imaging simulations also prove its ability in enhancing the defocus imaging.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10C
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• pp.1000-1010
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• 2006

This paper proposes a new architecture for DCT-based motion estimation and compensation. Previous methods do riot take sufficient advantage of the sparseness of 2-D DCT coefficients to reduce execution time. We first derive a recursion equation to perform DCT domain motion estimation more efficiently; we then use it to develop a wavefront array processor (WAP) consisting of processing elements. In addition, we show that the recursion equation enables motion predicted images with different frequency bands, for example, from the images with low frequency components to the images with low and high frequency components. The wavefront way Processor can reconfigure to different motion estimation algorithms, such as logarithmic search and three step search, without architectural modifications. These properties can be effectively used to reduce the energy required for video encoding and decoding. The proposed WAP architecture achieves a significant reduction in computational complexity and processing time. It is also shown that the motion estimation algorithm in the transform domain using SAD (Sum of Absolute Differences) matching criterion maximizes PSNR and the compression ratio for the practical video coding applications when compared to tile motion estimation algorithm in the spatial domain using either SAD or SSD.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.1
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• pp.28-34
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• 2015

Several parallelization methods that can be applied to High Efficiency Video Coding (HEVC) decoders are evaluated. The market requirements of high-resolution videos, such as Full HD and UHD, have been increasing. To satisfy the market requirements, several parallelization methods for HEVC decoders have been studied. Understanding these parallelization methods and objective comparisons of these methods are crucial to the real-time decoding of high-resolution videos. This paper introduces the parallelization methods that can be used in HEVC decoders and evaluates the parallelization methods comparatively. The experimental results show that the average speed-up factors of tile-level parallelism, wavefront parallel processing (WPP), frame-level parallelism, and 2D-wavefront parallelism are observed up to 4.59, 4.00, 2.20, and 3.16, respectively.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.101-106
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• 2016

A pupil filter is a useful technique for modifying the light intensity distribution near the focus of an optical system to realize depth of field (DOF) extension and superresolution. In this paper, we proposed a new design of the phase only pupil filter by using Zernike polynomials. The effect of design parameters of the new filters on DOF extension and superresolution are discussed, such as defocus Strehl ratio (S.R.), superresolution factor (G) and relative first side lobe intensity (M). In comparison with the other two types of pupil filters, the proposed filter presents its advantages on controlling both the axial and radial light intensity distribution. Finally, defocused imaging simulations are carried out to further demonstrate the effectiveness and superiority of the proposed pupil filter on DOF extension and superresolution in an optical imaging system.