An accurate measurement of the point spread function (PSF) for the extended depth of field (EDoF) cell phone camera with CMOS sensor is very important for image processing and image restoration. But due to the coarse sampling of the PSF by CMOS sensor, the overall system including the imaging subsystem and sampling subsystem is a shift-variant system with respect to the sample-scene phase parameter within sub-pixel range. In this paper, we present the sub-pixel digital algorithm to estimate the overall camera PSF based on the measurement of a high resolution PSF of the imaging lens. The sub-pixel digital algorithm averages the shifted high resolution PSFs of the lens over one active pixel area with the assumption of uniform random distribution of point source location within one active pixel area. Then the averaged high resolution PSF is down sampled onto Bayer plane to obtain the shift-invariant overall system PSF. We applied this shift-invariant PSF for image restoration of blurred images captured with an extended depth of field camera. The processed images are compared with originally captured images. Improvement of image quality is seen.

Date Published: 3 September 2008
PDF: 13 pages
Proc. SPIE 7072, Optics and Photonics for Information Processing II, 70720F (3 September 2008); doi: 10.1117/12.796034

Published in SPIE Proceedings Vol. 7072:
Optics and Photonics for Information Processing II
Abdul Ahad Sami Awwal; Khan M. Iftekharuddin; Bahram Javidi, Editor(s)