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Effects of nonlinear camera response function in spatial domain depth-from-defocus

[+] Author Affiliations
Soon-Yong Park

Kyungpook National University, Department of Computer Engineering, Daegu 702-701, Korea

J. Electron. Imaging. 16(3), 033021 (September 21, 2007). doi:10.1117/1.2774830
History: Received September 21, 2005; Revised February 15, 2007; Accepted February 22, 2007; Published September 21, 2007
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Most digital cameras incorporate nonlinear mapping from the amount of light falling onto an imaging sensor to a picture’s intensity. However, this nonlinear mapping would cause problems in some linear operations of image processing such as depth-from-defocus (DFD). We address the erroneous effects of the nonlinear response function of a digital still camera in DFD. A spatial-domain DFD technique called S-transform is employed to present the effects of the nonlinear mapping. To enhance DFD performance, we undistort the camera response function. Comparagrams of differently exposed multiple images are employed to estimate the response function. The estimated response function is then fitted to a piecewise linear function. To compare DFD performance, we use four different approaches of the S-transform for automatic focusing of the camera. Compensation of the nonlinear response function enhances AF performance of the camera and estimates blur parameters more accurately.

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Citation

Soon-Yong Park
"Effects of nonlinear camera response function in spatial domain depth-from-defocus", J. Electron. Imaging. 16(3), 033021 (September 21, 2007). ; http://dx.doi.org/10.1117/1.2774830


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