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Sensors 2015, 15(3), 5747-5762; doi:10.3390/s150305747

Sensor-Based Auto-Focusing System Using Multi-Scale Feature Extraction and Phase Correlation Matching

1
Image Processing and Intelligent System Laboratory Graduate School of Advanced Imaging Science, and Film Chung-Ang University, Seoul 156-756, Korea
2
Digital Design Team, SK Hynix, Gyeonggi-do 463-844, Korea
*
Author to whom correspondence should be addressed.
Academic Editor: Vittorio M.N. Passaro
Received: 4 January 2015 / Revised: 3 March 2015 / Accepted: 3 March 2015 / Published: 10 March 2015
(This article belongs to the Section Physical Sensors)
View Full-Text   |   Download PDF [13934 KB, uploaded 10 March 2015]   |  

Abstract

This paper presents a novel auto-focusing system based on a CMOS sensor containing pixels with different phases. Robust extraction of features in a severely defocused image is the fundamental problem of a phase-difference auto-focusing system. In order to solve this problem, a multi-resolution feature extraction algorithm is proposed. Given the extracted features, the proposed auto-focusing system can provide the ideal focusing position using phase correlation matching. The proposed auto-focusing (AF) algorithm consists of four steps: (i) acquisition of left and right images using AF points in the region-of-interest; (ii) feature extraction in the left image under low illumination and out-of-focus blur; (iii) the generation of two feature images using the phase difference between the left and right images; and (iv) estimation of the phase shifting vector using phase correlation matching. Since the proposed system accurately estimates the phase difference in the out-of-focus blurred image under low illumination, it can provide faster, more robust auto focusing than existing systems. View Full-Text
Keywords: auto-focusing; phase-difference; black mask; difference of Gaussian; phase correlation; hybrid auto-focusing auto-focusing; phase-difference; black mask; difference of Gaussian; phase correlation; hybrid auto-focusing
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Jang, J.; Yoo, Y.; Kim, J.; Paik, J. Sensor-Based Auto-Focusing System Using Multi-Scale Feature Extraction and Phase Correlation Matching. Sensors 2015, 15, 5747-5762.

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