KEYWORDS: Modulation transfer functions, Cameras, Optical signal processing, Lens design, Chromatic aberrations, Imaging systems, Point spread functions, Image processing, Digital signal processing, Computational imaging
In this paper we present an approach to extend the Depth-of-Field (DoF) for cell phone miniature camera by concurrently
optimizing optical system and post-capture digital processing techniques. Our lens design seeks to increase the
longitudinal chromatic aberration in a desired fashion such that, for a given object distance, at least one color plane of the
RGB image contains the in-focus scene information. Typically, red is made sharp for objects at infinity, green for
intermediate distances, and blue for close distances. Comparing sharpness across colors gives an estimation of the object
distance and therefore allows choosing the right set of digital filters as a function of the object distance. Then, by
copying the high frequencies of the sharpest color onto the other colors, we show theoretically and experimentally that it
is possible to achieve a sharp image for all the colors within a larger range of DoF. We compare our technique with other
approaches that also aim to increase the DoF such as Wavefront coding.
In this paper we present an approach to obtain an extended Depth-of-Field (DoF) for cell phone miniature camera by
jointly optimizing optical system and post-capture digital processing techniques. Using a computational imaging
approach, we demonstrate how to increase, to a useful operating range, the effective DoF of a specifically designed fixed
focus lens operating e.g. at f/2.8. This is achieved with a lens design where the longitudinal chromatic aberration has
been increased. This increase is controlled so as to have, for any distance within the extended DoF, at least one colour
channel of a RGB image which contains the in-focus scene information (e.g. high frequencies). By determining the
sharpest colour (for each region in the digital image) and reflecting its sharpness on the others, we show that it is possible
to get a sharp image for all colours through the merged DoF of the three of them. We compare our technique with other approaches that also aimed to increase the DoF such as Wavefront coding.
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