Improving the tolerance characteristics of small F/number compact camera module using wavefront coding

Abstract

We propose a novel optical design method for small F/number (F/#) compact camera module using wavefront coding. Decreasing the F/# decreases the focus depth of the optical system, which can result in manufacturing tolerances so tight that fabrication is impossible. To obtain reasonable tolerances for easy fabrication and alignment of compact camera module, we designed the final imaging system to have a target wavefront with an extended focus depth. Because additional optical elements, such as phase plates, are not available for compact camera modules, target wavefront should be the combination of the wavefront errors of all lenses in the optical system. Wavefront-coded compact camera modules have higher tolerances and an extended focus depth, so that the images obtained from them have high resolution over a broad defocus range. Images simulated by a wavefront-coded optical system can be restored to much higher resolution using deconvolution of images and a point spread function given by the coded target wavefront.