M. Hattori and S. Komatsu: Defocus Evaluation by the Deconvolution Filter Set Method: Experimental Investigation, Jpn. J Opt. (KOGAKU), Vol. 27 (1998) 150 -156.

Abstract: The deconvolution filter set method for evaluating the defocus amount, whose effectiveness has been confirmed by computer simulation in our latest research, is applied to a practical camera with a conventional zoom lens imaging real three-dimensional objects. A defocused image is deconvolved with the lens point spread functions measured in advance at various sets of the object-lens distance and object-detector distance. The quality of the deconvoled images are evaluated with the sum of the negative intensity values contained in each deconvolved image. The object distance and the image detector distance from the lens are determined as those which minimize the negative sum. It is experimentally shown that those distances are successfully determined for real objects and the clearly recovered images are also obtained at the same time.