Jeffrey H. Price, David Gough,
Abstract Reliable autofocus is required to obtain accurate measurements of fluorescent stained cellular components from a system capable of scanning multiple microscope fields. Autofocus could be performed directly with fluorescence images, but ... evaluate functions for both phase‐contrast and fluorescence autofocus and determine the suitability of phase‐contrast autofocus for fluorescence microscopy. Eleven autofocus functions were independently evaluated for fluorescence and phase‐ ... chosen from these and phase‐contrast and fluorescence autofocus were compared on scans each comprising more than ...
Tópico(s): Advanced Fluorescence Microscopy Techniques
1994 - Wiley | Cytometry
Jianlai Chen, Junchao Zhang, Hanwen Yu, Gang Xu, Buge Liang, Degui Yang, Hui Wang,
... beam width can result in a wide-beam autofocus problem in airborne synthetic aperture radar (SAR). Because ... method and its extensions are unsuitable for the autofocus of wide-beam SAR imaging. In addition, existing ... address these problems, we propose a wide-beam autofocus algorithm based on a blind nonlinear chirp scaling. ... the two-step MoCo method, the wide-beam autofocus in this study was modeled as a multiparameter ... known parametric and nonparametric methods in the SAR autofocus community to convert the multidimensional optimization problem into ...
Tópico(s): Antenna Design and Optimization
2022 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Computational Imaging
Jianlai Chen, Hanwen Yu, Gang Xu, Junchao Zhang, Buge Liang, Degui Yang,
Existing airborne SAR autofocus methods can be classified as parametric and non-parametric. Generally, non-parametric methods, such as the widely used phase gradient autofocus (PGA) algorithm, are only suitable for scenes with ... this issue, this article proposes an airborne SAR autofocus approach combined with blurry imagery classification to improve the autofocus efficiency for ensuring autofocus precision. In this approach, we embed the blurry ... in a deep learning community into the traditional autofocus framework as a preprocessing step before autofocus processing ...
Tópico(s): Microwave Imaging and Scattering Analysis
2021 - Multidisciplinary Digital Publishing Institute | Remote Sensing
Zhonglin Wu, D.H. Wang, Fangfang Zhou,
... this paper, a bilateral prediction and intersection calculation autofocus method for automated microscopy, which obtains the in- ... curve, is proposed and performed. According to the autofocus method, the area including the peak position of ... be considered as the in-focus position. The autofocus can be realized by moving the focus plane ... curves. The proposed bilateral prediction and intersection calculation autofocus method is experimentally verified in an automated light ... that the proposed bilateral prediction and intersection calculation autofocus method can not only effectively avoid the principle ...
Tópico(s): Digital Holography and Microscopy
2012 - Wiley | Journal of Microscopy
Wilfried Boecker, W. Rolf, Walter Müller, C. Streffer,
A reliable autofocus is necessary for any combined image processing and automated microscope system analyze scan areas larger than a single field. Autofocus functions for brightfield microscopy have been reported in the literature. Autofocus implementations for fluorescence microscopy have to deal with ... faintness of the fluorescent light. In this presentation autofocus procedures are introduced for fluorescence microscopy based on ... with a PC. We have constructed a digital autofocus system as well as an analogue autofocus detector. ...
Tópico(s): Cell Image Analysis Techniques
1996 - SPIE | Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE
... or signal propagation delays. We present a new autofocus algorithm, termed Fourier-domain multichannel autofocus (FMCA), that is derived under a linear algebraic ... in a noniterative fashion. Motivated by the mutichannel autofocus (MCA) approach, the proposed autofocus algorithm invokes the assumption of a low-return ... SAR and bistatic SAR scenarios. Most previous SAR autofocus algorithms rely on the prior assumption that radar' ... made regarding the SAR scene. Performance of such autofocus algorithms degrades if the assumptions are not satisfied. ...
Tópico(s): Microwave Imaging and Scattering Analysis
2011 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Image Processing
Jincheng Li, Jie Chen, Pengbo Wang, Otmar Loffeld,
An autofocus operation is an indispensable procedure to obtain well-focused images for synthetic-aperture radar (SAR) systems without ... in the very high-resolution (VHR) airborne SAR autofocus due to the long cumulative time: the varying ... When it comes to the stripmap mode, the autofocus becomes more complicated, since the scenario with a ... beam. Combining the merits of parametric and nonparametric autofocus algorithms, a robust motion error estimation method is ... paper. First, we perform a stripmap multiaperture mapdrift autofocus operation to extract the along-track velocity and ...
Tópico(s): Microwave Imaging and Scattering Analysis
2018 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Geoscience and Remote Sensing
... using information from an inertial measurement unit (IMU). Autofocus techniques, which focus SAR images, produce an ‘autofocus parameter’ which is related to the platform motion. ... to support the assumption that the contrast optimization autofocus algorithm behaves as a least-squares quadratic fitting ... trajectory. Using this assumption, the relationship between the autofocus parameter and across-track accelerations of the SAR ... SAR platform motion to be estimated from the autofocus parameter measurements and incorporated in a motion compensation ...
Tópico(s): Target Tracking and Data Fusion in Sensor Networks
1991 - Taylor & Francis | International Journal of Remote Sensing
Voon Chet Koo, Yee Kit Chan, H. T. Chuah,
Abstract This paper deals with the SAR autofocus problem, with the aim to implement the proposed autofocus algorithm in real-time. The crux of the SAR autofocus problem is to estimate the phase error e (·) ... phase error from the SAR data. The existing autofocus algorithms are mostly performed off-line as part ... is due to the fact that the conventional autofocus methods require the entire synthetic aperture length for ... proposed algorithm, called the Multiple Phase Difference (MPD) Autofocus, utilises the maximum likelihood (ML) principle to solve ...
Tópico(s): Spectroscopy Techniques in Biomedical and Chemical Research
2006 - Taylor & Francis | Journal of Electromagnetic Waves and Applications
Feimo Shen, Louis Hodgson, Jeffrey H. Price, Klaus M. Hahn,
... studying intracellular protein dynamics in individual, living cells. Autofocus is valuable in such studies to compensate for ... by the meniscus in microtiter plates, we studied autofocus in differential interference contrast (DIC) microscopy with a ... for measuring image sharpness. Repeated tests of DIC autofocus with this digital filter on 225 fields-of- ... a precision of 8.6 nm (standard deviation). Autofocus trials on specimens with thicknesses from 9.47 ... mum, controlled by cell plating density, showed that autofocus precision was independent of specimen thickness. The results ...
Tópico(s): Digital Holography and Microscopy
2008 - Wiley | Cytometry Part A
Haemin Lee, Chang-Sik Jung, Ki-Wan Kim,
Autofocus is an essential technique for airborne synthetic aperture radar (SAR) imaging to correct phase errors mainly ... motion error. There are several well-known conventional autofocus methods such as phase gradient autofocus (PGA) and minimum entropy (ME). Although these methods ... computation burden, etc. In this paper, feature preserving autofocus (FPA) algorithm is newly proposed. The algorithm is ... existing regularization-based algorithms such as sparsity-driven autofocus (SDA). This difference makes the proposed method far ...
Tópico(s): Synthetic Aperture Radar (SAR) Applications and Techniques
2021 - Multidisciplinary Digital Publishing Institute | Sensors
Karlus A. C. de Macedo, Rolf Scheiber, Alberto Moreira,
... for the first time the use of the autofocus technique for residual motion errors in the repeat-pass interferometric context. A very robust autofocus technique has to be used to cope with ... repeat-pass applications. We propose a new robust autofocus algorithm based on the weighted least squares phase estimation and the phase curvature autofocus (PCA) extended to the range-dependent case. We ... new algorithm weighted PCA. Different from multisquint, the autofocus approach has the advantage of being able to ...
Tópico(s): Soil Moisture and Remote Sensing
2008 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Geoscience and Remote Sensing
There are numerous passive contrast sensing autofocus algorithms that are well documented in literature, but some aspects of their comparative performance have not been widely researched. This study explores the relative merits of a set of autofocus algorithms via examining them against a variety of ... then computes the best focal position using each autofocus algorithm. The process is repeated across a survey ... derive conclusions about the relative merits of each autofocus algorithm with respect to the criteria accuracy and ...
Tópico(s): Cell Image Analysis Techniques
2007 - SPIE | Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE
R. L. Morrison, N. Minh, David C. Munson,
Synthetic aperture radar (SAR) autofocus techniques that optimize sharpness metrics can produce excellent restorations in comparison with conventional autofocus approaches. To help formalize the understanding of metric-based SAR autofocus methods, and to gain more insight into their ... for the specific case of intensity-squared minimization autofocus, the mechanism by which metric-based methods utilize the multichannel defocusing model of SAR autofocus to enforce the stationary point property for multiple ...
Tópico(s): Optical measurement and interference techniques
2007 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Image Processing
Trond Varslot, Andrew Kingston, Glenn R. Myers, Adrian Sheppard,
... In this paper we show that optimization-based autofocus may be used to overcome the instabilities that ... computed tomography (micro-CT) imaging. We show that autofocus-corrected, theoretically-exact helical CT is a viable ... trajectory and an ideal helix, and use an autofocus method to estimate the relevant parameters. We define ... applied. Results: We make significant modifications to the autofocus method that allow this method to be used ... 1PI (K1PI) inversion formula. We further demonstrate how autofocus-corrected, theoretically-exact helical CT reduces the image ...
Tópico(s): Image Processing Techniques and Applications
2011 - Wiley | Medical Physics
Kuang-Hung Liu, Ami Wiesel, David C. Munson,
The autofocus problem in synthetic aperture radar imaging amounts to estimating unknown phase errors caused by unknown platform or ... the heart of three state-of-the-art autofocus algorithms, namely, phase gradient autofocus, multichannel autofocus (MCA), and Fourier-domain multichannel autofocus (FMCA), is the solution of a constant modulus ...
Tópico(s): Synthetic Aperture Radar (SAR) Applications and Techniques
2013 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Image Processing
Seonghyeon Lee, Ji‐Hoon Bae, Min‐Seok Kang, Kyung‐Tae Kim,
... new and efficient inverse synthetic aperture radar (ISAR) autofocus technique by introducing eigenimages to boost the speed of the traditional autofocus algorithms. First, a preprocessing step is applied to ... eigenvectors corresponding to the dominant eigenvalues. Finally, traditional autofocus methods are combined with the proposed signal eigenimage ... significantly lower the computational complexity of the traditional autofocus methods because the dimensionality of the signal eigenimage ... that are comparable to those of the traditional autofocus methods in terms of image focal quality. Several ...
Tópico(s): Synthetic Aperture Radar (SAR) Applications and Techniques
2016 - Institute of Electrical and Electronics Engineers | IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
Wei Pu, Wenchao Li, Junjie Wu, Yulin Huang, Jianyu Yang, Haiguang Yang,
... bistatic forward-looking synthetic aperture radar (BFSAR), conventional autofocus algorithms cannot estimate the phase errors accurately when ... estimation-evaluation-equalization scheme is proposed before conventional autofocus for BFSAR. Different from the conventional autofocus method, the azimuth-variant Doppler coefficients are additionally estimated and equalized before autofocus, and as a consequence, phase errors can be ... of the proposed method on the improvement of autofocus in BFSAR.
Tópico(s): Microwave Imaging and Scattering Analysis
2017 - Institute of Electrical and Electronics Engineers | IEEE Geoscience and Remote Sensing Letters
Yixiong Liang, Meng Yan, Zhihong Tang, Zhujun He, Jianfeng Liu,
Autofocus is an essential part of modern high-throughput optical microscopic imaging system, and the traditional passive autofocus algorithms such as hill climbing search are heuristics ... the heuristics, in this paper we treat the autofocus as a regression problem and propose to learn ... basic and combined features for faster and better autofocus. Finally, we comprehensively evaluate our methods on a ... cell images. Our Defocus of Focus (DFF)-based autofocus shows improved accuracy over previous work from 97. ...
Tópico(s): Cell Image Analysis Techniques
2019 - Elsevier BV | Optik
Xuaner Zhang, Kevin Matzen, Vivien Nguyen, Dillon Yao, You Zhang, Ren Ng,
... analyzes future video frames to deliver context-aware autofocus for the current frame. To create refocusable video, ... choose focus accurately for each frame, we demonstrate autofocus that looks at upcoming video frames and applies ... audio and saliency detection. We also show that autofocus benefits from machine learning and a large-scale ... for example, a shallow DOF video where the autofocus transitions onto each person before she begins to speak. This is impossible for conventional camera autofocus because it would require seeing into the future.
Tópico(s): Advanced Image Processing Techniques
2019 - Association for Computing Machinery | ACM Transactions on Graphics
Jinjian Cai, Marco Martorella, Shaoqiang Chang, Quanhua Liu, Zegang Ding, Teng Long,
Phase autofocus is a significant step in translational motion compensation for inverse synthetic aperture radar (ISAR) imaging. Among the existing autofocus methods, contrast maximization-based algorithms are superior in accuracy and robustness. However, the existing maximum contrast autofocus methods are parametric, which significantly affects their convergence ... paper, a novel non-parametric maximum contrast ISAR autofocus algorithm based on Newton's method is proposed ... established non-parametric method, namely the minimum entropy autofocus method. It will be shown that the proposed ...
Tópico(s): Spectroscopy Techniques in Biomedical and Chemical Research
2020 - IEEE Sensors Council | IEEE Sensors Journal
Hao Lin, Jianlai Chen, Mengdao Xing, Xiaoxiang Chen, Dong You, Guang‐Cai Sun,
In the existing time-domain autofocus algorithms, the azimuth deramping operation will change the azimuth-independent phase into the azimuth-dependent phase, which may greatly reduce the accuracy of autofocus processing in squint spotlight synthetic aperture radar (SAR). In contrast, the frequency-domain autofocus algorithms can avoid this problem because it does ... azimuth deramping operation. However, the existing frequency-domain autofocus algorithms are proposed based on the assumption of ... Therefore, this article extends the existing frequency-domain autofocus algorithm to the squint mode combined with the ...
Tópico(s): Microwave Imaging and Scattering Analysis
2021 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Geoscience and Remote Sensing
... was developed to achieve single- and dual-direction autofocus control. An improved autofocus method, which is based on the error between ... error was used to predict the number of autofocus operation steps required to approach a near-focus ... to capture live images of the target. The autofocus experiments carried out using the new differential error- ... be 40 s in comparison with the normal autofocus algorithm.
Tópico(s): Advanced Fluorescence Microscopy Techniques
2009 - SPIE | Optical Engineering
... focused image. Techniques that do this are termed "autofocus" algorithms. A very popular autofocus algorithm is the Phase Gradient Autofocus (PGA) algorithm. The nearly universal, and typically reasonable, ... apparent motion errors exceeds the range resolution, conventional autofocus algorithms fail. Excessive residual migration is increasingly encountered ... due to atmospheric phenomena). A new migration-correction autofocus algorithm has been developed that estimates the excessive ...
Tópico(s): Sparse and Compressive Sensing Techniques
2005 - SPIE | Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE
The phase gradient autofocus (PGA) and its improvements have been aimed to estimate the phase error exclusively from the phase of raw data. ... filter (KF) into stripmap PGA (or phase curvature autofocus) by taking advantage of the continuous movement of ... This helps real-time synthetic aperture radar (SAR) autofocus and motion compensation. The disciplining of the autofocus using KF is not restricted to PGA-based ... It can be applied to other subaperture-based autofocus algorithms.
Tópico(s): Radar Systems and Signal Processing
2020 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Geoscience and Remote Sensing
Three dimensional (3D) autofocus remains a significant challenge for the development of practical 3D multipass radar imaging. The current 2D radar autofocus methods are not readily extendable across sensor passes. ... that is simultaneously solved for scatterer heights and autofocus parameters. The proposed method extends 2-pass interferometric ... height locations. A specific case from the proposed autofocus framework is solved and demonstrates autofocus and coherent multipass 3D estimation across the 8 ...
Tópico(s): Microwave Imaging and Scattering Analysis
2008 - SPIE | Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE
Richard M. Naething, R. Derek West,
... of data-driven phase error mitigation known as autofocus. We present results comparing the performance of a variety of autofocus techniques including image metric optimization based techniques and several variants of phase gradient autofocus (PGA). The degree of focusing is evaluated with ... images, that is not biased toward any particular autofocus algorithm. This evaluation is performed on a variety ... injected (known) phase errors. We show that PGA autofocus outperforms the image metric optimization techniques tested (based ...
Tópico(s): Cell Image Analysis Techniques
2013 - SPIE | Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE
Byoung Goo Jeon, Byung Je Jung, Hong Jin Kong, Yong Hoon Cho,
The autofocus method has been investigated to improve the precise positioning of a substrate surface at the center of ... nanofabrication. For this purpose, we developed a novel autofocus method using normalized image size, which was calculated ... proposed method enhanced the precision and robustness of autofocus in TPP. Specifically, the experimental creation of ascending ... To test the practical feasibility of the proposed autofocus method, 300 μm×260 μm single-layer honey- ... with precompensation and dynamic compensation using the proposed autofocus method.
Tópico(s): Nanofabrication and Lithography Techniques
2015 - Optica Publishing Group | Applied Optics
Charles V. Jakowatz, Daniel E. Wahl,
... to back-projection. The application of a traditional autofocus algorithm, such as Phase Gradient Autofocus (PGA), requires some care in this situation. Specifically, ... is a Cartesian grid in the ground plane. Autofocus via PGA for such an image, however, cannot ... this paper we propose a strategy for performing autofocus in this situation, and discuss its limitations. We ...
Tópico(s): Sparse and Compressive Sensing Techniques
2009 - SPIE | Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE
Lawrence M. Firestone, K. Cook, Kevin Culp, Neil Talsania, Kendall Preston,
Abstract Traditional autofocus methods were designed for microscopes driven by single processor computers. As computers are developed that exploit massive parallelism ... the reader to both cellular logic techniques for autofocus and a new spectral moment autofocus measure. It then compares these methods with more traditional autofocus methods. It is shown that traditional methods based ...
Tópico(s): Cell Image Analysis Techniques
1991 - Wiley | Cytometry