检索结果-内蒙古大学图书馆

Information content analysis in automated microscopy imaging using an adaptive autofocus algorithm for multimodal functions

引用

JOURNAL OF MICROSCOPY 2009年第3期236卷 194-202页

作者： Brazdilova, S. L. Kozubek, M. Masaryk Univ Fac Informat Ctr Biomed Image Anal Brno Czech Republic

P>We present a new algorithm to analyse information content in images acquired using automated fluorescence microscopy. The algorithm belongs to the group of autofocusing methods, but differs from its predecessors in that it can handle thick specimens and operate also in confocal mode. It measures the information content in images using a 'content function', which is essentially the same concept as a focus function. Unlike previously presented algorithms, this algorithm tries to find all significant axial positions in cases where the content function applied to real data is not unimodal, which is often the case. This requirement precludes using algorithms that rely on unimodality. Moreover, choosing a content function requires careful consideration, because some functions suppress local maxima. First, we test 19 content functions and evaluate their ability to show local maxima clearly. The results show that only six content functions succeed. To save time, the acquisition procedure needs to vary the step size adaptively, because a wide range of possible axial positions has to be passed so as not to miss a local maximum. The algorithm therefore has to assess the steepness of the content function online so that it can decide to use a bigger or smaller step size to acquire the next image. Therefore, the algorithm needs to know about typical behaviour of content functions. We show that for normalized variance, one of the most promising content functions, this knowledge can be obtained after normalizing with respect to the theoretical maximum of this function, and using hierarchical clustering. The resulting algorithm is more reliable and efficient than a simple procedure with constant steps.

关键词： autofocus algorithm automated microscopy content function information content analysis multimodal focus function normalized variance

来源：评论

学校读者我要写书评

暂无评论

Study on Improvement of Phase Gradient autofocus algorithm

Study on Improvement of Phase Gradient Autofocus Algorithm

引用

1st International Workshop on Education Technology and Computer Science

作者： Tang, Haoyang Shi, Haoshan Qi, Changyuan Northwestern Polytech Univ Coll Elect Informat Xian 710072 Peoples R China Northwest Univ Xian Coll Informat Sci & Technol Xian Peoples R China

ISBN: (纸本)9780769535579

Based on the theory of Phase Gradient autofocus on airborne SAP, an improved algorithm for reducing the Phase Gradient autofocus computation is provided in this paper. According to the image contrast criterion, some isolated stronger scatters for estimation phase errors are chosen, and then a new way to select windows width is developed, which can accelerate the convergence of the autofocus. Point target simulation is carried out, which verify the feasibility and the validity of this algorithm. The present algorithm can estimate discretional. rank phase errors and doesn't require strong reflection point, which is up to accuracy. After decreasing the computation of this algorithm, it is more suitable for Real-time processing.

关键词： synthetic aperture radar Phase Gradient autofocus phase error autofocus algorithm

来源：评论

学校读者我要写书评

暂无评论

The Research on autofocus System of Miniature Five-coordinate Image Measuring Machine

The Research on Autofocus System of Miniature Five-coordinat...

引用

2nd International Conference on Frontiers of Manufacturing and Design Science (ICFMD 2011)

作者： Luo, Gang Chen, Zhiyuan Fei, Zhigen Henan Tech Coll Construct Zhengzhou 450064 Henan Peoples R China Zhengzhou Univ Light Ind Mech & Elect Engn Dept Zhengzhou 450002 Peoples R China

ISBN: (纸本)9783037852828

In order to meet the high-precision measurement requirement of tested objects with tiny dimension and complex shape, a miniature five-coordinate image measuring machine, which contains three translational axes and two rotational axes, is designed and built. This machine can inspect the objects from multi-orientation and multi-posture in non-contact way. As an indispensable step of image measurement, the autofocus effect has a direct influence on the following image quality and measurement accuracy. In this paper, the composition and working principle of autofocus system are presented and discussed. Meanwhile, the path planning method for autofocus system is introduced and an autofocus method based on evaluation function of mean square deviation is proposed and discussed in detail. Finally, the experiments demonstrate the effectiveness of the method and the accuracy of autofocus system.

关键词： Five-coordinate measuring machine autofocus algorithm Image measurement Path planning

来源：评论

学校读者我要写书评

暂无评论

Simulations of Optical autofocus algorithms Based on PGA in SAIL

Simulations of Optical Autofocus Algorithms Based on PGA in ...

引用

Conference on Applications of Digital Image Processing XXXIV

作者： Xu, Nan Liu, Liren Xu, Qian Zhou, Yu Sun, Jianfeng Chinese Acad Sci Shanghai Inst Opt & Fine Mech Shanghai 201800 Peoples R China

ISBN: (纸本)9780819487452

The phase perturbations due to propagation effects can destroy the high resolution imagery of Synthetic Aperture Imaging Ladar (SAIL). Some autofocus algorithms for Synthetic Aperture Radar (SAR) were developed and implemented. Phase Gradient algorithm (PGA) is a well-known one for its robustness and wide application, and Phase Curvature algorithm (PCA) as a similar algorithm expands its applied field to strip map mode. In this paper the autofocus algorithms utilized in optical frequency domain are proposed, including optical PGA and PCA respectively implemented in spotlight and strip map mode. Firstly, the mathematical flows of optical PGA and PCA in SAIL are derived. The simulations model of the airborne SAIL is established, and the compensation simulations of the synthetic aperture laser images corrupted by the random errors, linear phase errors and quadratic phase errors are executed. The compensation effect and the cycle index of the simulation are discussed. The simulation results show that both the two optical autofocus algorithms are effective while the optical PGA outperforms the optical PCA, which keeps consistency with the theory.

关键词： image processing synthetic aperture imaging ladar autofocus algorithm PGA

来源：评论

学校读者我要写书评

暂无评论

Implementation of autofocus in Alignment System for Layered Imprint Fabrication

引用

Transactions of Tianjin University 2009年第4期15卷 294-299页

作者：王权岱段玉岗卢秉恒向家伟杨连发 State Key Lab for Manufacturing Systems Engineering Xi'an Jiaotong University School of Mechanical and Electrical Engineering Guilin University of Electronic Technology

autofocus method based on the analysis of image content information is investigated to reduce the alignment error resulting from mark positioning uncertainty due to defocus in microstructure layered fabrication process based on multilevel imprint lithography. The applicability of several autofocus functions to the alignment mark images is evaluated concerning their uniformity, sharpness near peak, reliability and measure computation efficiency and the most suitable one based on power spectrum in frequency domain (PSFD) is adopted. To solve the problem of too much computation amount needed in PSFD algorithm, the strategy of interested region detection and effective image reconstruction is proposed and the algorithm efficiency is improved. The test results show that the computation time is reduced from 0.316 s to 0.023 s under the same conditions while the other merits of the function are preserved, which indicates that the modified algorithm can meet the mark image autofocusing requirements in response time, accuracy and robustness. The alignment error due to defocus which is about 0.5 μm indicated by experimental results can be reduced or eliminated by the autofocusing implementation.

关键词： autofocus algorithm alignment imprint lithography layered fabrication

来源：评论

学校读者我要写书评

暂无评论

Real-time implementation issues in passive automatic focusing for digital still cameras

引用

JOURNAL OF IMAGING SCIENCE AND TECHNOLOGY 2005年第2期49卷 114-123页

作者： Peddigari, V Gamadia, M Kehtarnavaz, N Univ Texas Dept Elect Engn Richardson TX USA

Due to consumers' demand for faster picture shot time in the rapidly expanding digital still camera market, it is of importance to address the real-time implementation issues in the development of passive automatic focusing for digital still cameras. This article discusses such real-time implementation issues that are often overlooked when designing passive contrast sensing automatic focusing on digital still camera processors. Specifically, algorithmic design tradeoffs between automatic focusing speed, accuracy, and power consumption, are addressed. A sample implementation and its performance results on an actual digital still camera hardware platform powered by the Texas Instruments TMS320DM270 processor are presented to further convey these real-time implementation issues.

关键词： autofocus algorithm

来源：评论

学校读者我要写书评

暂无评论

IMPROVEMENT OF PHASE GRADIENT autofocus algorithm

引用

Chinese Journal of Aeronautics 1998年第3期11卷 33-39页

作者：李立伟毛士艺刘莹 Department of Electronic Engineering Beijing Univ. Aero. and Astronaut. Beijing 100083 China

The phase error estimated by phase gradient autofocus(PGA) is not based on a finite order polynomial mode, so PGA has a good autofocus property for arbitrary order phase error and is fit for high resolution airborne SAR. But PGA has two shortcomings: first, it has a worse estimation property for fast changing phase error; second, there exists a section of linear phase in the phase error estimated by this algorithm. This paper introduces the idea of rank one phase estimate (ROPE) autofocus technique, and improves PGA. The improved PGA(IPGA) can successfully overcome both these shortcomings of PGA.

关键词： high resolution airborne SAR autofocus algorithm phase gradient autofocus(PGA) rank one phase estimation(ROPE)

来源：评论

学校读者我要写书评

暂无评论

Improvement of Rank One Phase Estimation(ROPE) autofocusing Technique

Improvement of Rank One Phase Estimation(ROPE) Autofocusing ...

引用

1998 Fourth International Conference Signal Processing

作者： Li Liwei Asif Raza Mao Shiyi Group 203 Dept. of E.E.Beijing Univ.of Aeronautics and Astronautics

This paper presents an improved rank one phase error estimate(ROPE) autofocus technique. Compared with ROPE,the improved algorithm(IROPE) has two distinct ***,its model is more actual,so its property of robustness is ***,at the beginning of it's iteration process,the initialized valves are set up *** approximation is more exact as compared to the blind initialization of *** estimator of phase error is maximum-likelihood (ML) one,and,under some special conditions, its estimator is the same as mat of phase gradient autofocus(PGA),which is linear unbiased minimum variation(LUMV) *** ROPE and PGA are subsets of IROPE.

关键词： SAR autofocus algorithm

来源：评论

学校读者我要写书评

暂无评论

SUBAPERTURE autofocus FOR SYNTHETIC-APERTURE RADAR

引用

IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 1994年第2期30卷 617-621页

作者： CALLOWAY, TM DONOHOE, GW UNIV NEW MEXICO ALBUQUERQUENM 87131

A subaperture autofocus algorithm for synthetic aperture radar (SAR) partitions range-compressed phase-history data collected over a full aperture into equal-width subapertures. Application of a one-dimensional Fourier transform to each range bin converts each subaperture data set into a full-scene image (map). Any linear phase difference, or phase ramp, between a pair of subapertures expresses itself as cross-range drift in their maps. A traditional autofocus algorithm fits a polynomial to inferred equal-width phase ramps. If the true phase error function contains significant high-order components, then polynomial regression generates a poor estimate of the phase error function. Instead of fitting a polynomial, we fit a sinusoidal function through the inferred phase ramps. An example with a degraded SAR image shows how a sinusoidal correction improves image quality. We compare lower bounds on mean squared error (MSE) for polynomial and sinusoidal parameterizations. Sinusoidal parameterization reduces MSE significantly for model orders greater than five.

关键词： error analysis error statistics parameter estimation radar interference radar theory radiofrequency interference signal detection synthetic aperture radar SAR autofocus algorithm cross-range drift degraded SAR image equal-width subapertures full-scene im Radar theory signal acquisition Parameter estimation Polynomial auto-focus Sinusoidal functions Mean square error Rescue Radiofrequency interference Specific absorption rate

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：