Accurate and Rapid Auto-Focus Methods Based on Image Quality Assessment for Telescope Observation

Yang, Chunping; Chen, Minhao; Zhou, Fangfang; Li, Wei; Peng, Zhenming

doi:10.3390/app10020658

Cited by 21 publications

(12 citation statements)

References 32 publications

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“…Therefore, the traditional Tenengrad method is adopted in this paper. This method not only can reduce the occurrence of local extremum after selecting a certain threshold [31], but also has good sensitivity and accuracy [32,33]. It is a common image clarity evaluation function based on gradient.…”

Section: Image Quality Evaluationmentioning

confidence: 99%

Fast Blind Deblurring of QR Code Images Based on Adaptive Scale Control

et al. 2021

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With the development of 5G technology, the short delay requirements of commercialization and large amounts of data change our lifestyle day-to-day. In this background, this paper proposes a fast blind deblurring algorithm for QR code images, which mainly achieves the effect of adaptive scale control by introducing an evaluation mechanism. Its main purpose is to solve the out-of-focus caused by lens shake, inaccurate focus, and optical noise by speeding up the latent image estimation in the process of multi-scale division iterative deblurring. The algorithm optimizes productivity under the guidance of collaborative computing, based on the characteristics of the QR codes, such as the features of gradient and strength. In the evaluation step, the Tenengrad method is used to evaluate the image quality, and the evaluation value is compared with the empirical value obtained from the experimental data. Combining with the error correction capability, the recognizable QR codes will be output. In addition, we introduced a scale control parameter to study the relationship between the recognition rate and restoration time. Theoretical analysis and experimental results show that the proposed algorithm has high recovery efficiency and well recovery effect, can be effectively applied in industrial applications.

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Section: Image Quality Evaluationmentioning

confidence: 99%

Fast Blind Deblurring of QR Code Images Based on Adaptive Scale Control

et al. 2021

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“…TABLE III given below provides a comparison of our proposed solution with a similar recent auto-focus study [8] done on telescopic images.…”

Section: A Comparison With a Recent Studymentioning

confidence: 99%

“…The study [8] focuses on visible spectrum images and uses the measure of Tenengrad as the focusing measure. Moreover a single controller (hill-climbing method) is employed with dynamic adaptive focusing window to help find regions of interest and reducing computation time.…”

Section: A Comparison With a Recent Studymentioning

confidence: 99%

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Passive Autofocusing System for a Thermal Camera

et al. 2020

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Most of the Thermal (Infrared) cameras nowadays are equipped with a motorized lens for focusing a scene manually. The subjective nature of manual focusing makes it an inefficient and cumbersome process. In contrast, Autofocusing (AF) obtains the best focused image based on a quantitative measure with the benefits of convenience and intelligence. Various AF systems for visual cameras have been developed, but relatively less amount of work has been done for thermal imaging systems. This paper presents a Vision and Control based Autofocusing System (VCAFS) comprising: (1) an uncooled thermal camera with motorized lens, (2) a passive contrast-based focus measure, (3) a smoothing operator to avoid local extrema, and (4) two different lens motion controllers. Experimental results show the efficacy of the proposed system on live videos even when the scene and its depth are continuously changing. INDEX TERMS Contrast detection, Focus measures, Passive Autofocusing, Thermal imaging system.

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“…By hill-climbing searching, determining the peak value can help to determine the required focus based on a simple configuration, which is easy to handle and stable but rather time-consuming and has a very limited effective depth of focus. We have found that many research articles [31][32][33][34][35][36][37] have investigated the improvement of the algorithm using software and tried to make the application of the technique to the product line possible.…”

Section: Introductionmentioning

confidence: 99%

Implementation and Optimization of a Dual-confocal Autofocusing System

Jan

Liu

Yang

2020

Sensors

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This paper describes the implementation and optimization of a dual-confocal autofocusing system that can easily describe a real-time position by measuring the response signal (i.e., intensity) of the front and the rear focal points of the system. This is a new and systematic design strategy that would make it possible to use this system for other applications while retrieving their characteristic curves experimentally; there is even a good chance of this technique becoming the gold standard for optimizing these dual-confocal configurations. We adopt two indexes to predict our system performance and discover that the rear focal position and its physical design are major factors. A laboratory-built prototype was constructed and demonstrated to ensure that its optimization was valid. The experimental results showed that a total optical difference from 150 to 400 mm significantly affected the effective volume of our designed autofocusing system. The results also showed that the sensitivity of the dual-confocal autofocusing system is affected more by the position of the rear focal point than the position of the front focal point. The final optimizing setup indicated that the rear focal length and the front focal length should be set at 200 and 100 mm, respectively. In addition, the characteristic curve between the focus error signal and its position could successfully define the exact position by a polynomial equation of the sixth order, meaning that the system can be straightforwardly applied to an accurate micro-optical auto-focusing system.

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Accurate and Rapid Auto-Focus Methods Based on Image Quality Assessment for Telescope Observation

Cited by 21 publications

References 32 publications

Fast Blind Deblurring of QR Code Images Based on Adaptive Scale Control

Fast Blind Deblurring of QR Code Images Based on Adaptive Scale Control

Passive Autofocusing System for a Thermal Camera

Implementation and Optimization of a Dual-confocal Autofocusing System

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