Application of spatial-domain convolution/deconvolution transform for determining distance from image defocus

This paper describes the application of a new Spatial-Domain Convolution/Deconvolution transform (S transform) for determining distance of objects and rapid autofocusing of camera systems using image defocus. The method of determining distance, named STM, involves simple local operations on only a few (about 2 to 4) images and it can be easily implemented in parallel. STM has been implemented on an actual camera system named SPARCS. Experiments on the performance of STM and their results on real-world objects are presented. The results indicate that STM is useful in practical applications. The utility of the method is demonstrated for rapid autofocusing of electronic cameras. STM is computationally more efficient than other methods, but for our camera system, it is somewhat less robust in the presence of noise than a Fourier transform based approach. STM is a useful technique in many applications such as rapid autofocusing.