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Research on Digital Auto-Focusing System Based on Embedded Linux

Author: WangJianHua
Tutor: DengHuaQiuï¼›DengYunLong
School: South China University of Technology
Course: Optics
Keywords: Autofocus Embedded Linux Video surveillance
CLC: TP391.41
Type: Master's thesis
Year: 2011
Downloads: 112
Quote: 1
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Abstract


Autofocus capability is an important indicator for the evaluation of image quality, the key technology to help improve the competitiveness of the digital imaging products. The complexity of the scene due to the focus, auto-focus technology focusing evaluation function, the focus window, the search algorithm, focusing monitoring and exposure control, there are still problems, further research is needed, in order to improve the accuracy of the AF speed. Access to large amounts of literature on the basis of a detailed analysis of the basic theory of autofocus technology and research for the existing AF existing depth: First, the HSI color analysis focusing evaluation function. The analysis showed that the use of the HSI analysis focusing evaluation function as a color image and select energy function to meet the accuracy requirements at the same time be able to significantly improve focus speed. Secondly, the design of the integrated search algorithm. (1) generally focus search is easy to fall into focus local peak curve, improved traditional climbing search method - evaluation function value of the continuous decline over the focus curve peak twice before that, and set the decline threshold; (2 climbing search method) in the case of the optical zoom range lens focusing mirror group deviate from, has been unable to get out the local peak, the upper and lower limits of the range of known lens focus improved traditional exhaustive search method, to avoid falling into the local peak while also improving the focus of the convergence rate; (3) the Focus process in the scene may be disturbed, and focus to complete and then check whether the scene correctly avoided due to interference mistakenly focus; (4) can not be under low light focusing evaluation Close search. Again, raised from the change of light intensity, the scene changes, the scenes whether stationary and is engulfed in four local peak focus monitoring, motion detection and monitoring algorithms design time compared to adopt a different strategy, based on the results of the monitoring. Then, the proposed the nonlinear auto iris control algorithm. Due to the influence of light sensitivity, automatic gain, the aperture and light intensity are nonlinear, the need for multiple measurements in order to achieve accurate control. Finally, the autofocus system based on embedded Linux. Design drivers, applications and algorithms. The experimental results show that the system is able to achieve fast and accurate auto focus and exposure.

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CLC: > Industrial Technology > Automation technology,computer technology > Computing technology,computer technology > Computer applications > Information processing (information processing) > Pattern Recognition and devices > Image recognition device
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