Parametric point spread function modeling and reduction of stray light effects in digital still cameras
Burak Bitlis, Peter A. Jansson, Jan P. Allebach · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2007
In any real optical imaging system, some portion of the entering light flux is misdirected to undesired locations due to scattering from surface imperfections and multiple reflections between optical elements. This unwanted light is called stray light. Its effects include lower contrast, reduced detail, and color inaccuracy. Accurate removal of stray-flux effects first requires determination of the stray light point-spread function (PSF) of the system. For digital still cameras, we assume a parametric, shift-variant, rotationally invariant PSF model. For collection of data to estimate the parameters of this model, we use a light source box that provides nearly uniform illumination behind a circular aperture. Several images of this light source are captured when it is at different locations in the field of view of the camera. Also, another exposure of each scene with a different shutter speed is used to provide details in the darker regions. A subset of the data obtained from these images is used in a nonlinear optimization algorithm. After estimating the parameters of the PSF model, we provide the results of applying the correction algorithm to the images taken of real world scenes.