Automatic focusing of optical images

摘要

Disclosed is a device for automatically focusing optical images wherein a rotating transparent disk having at least two sections of different focus delay characteristics is operative to pass a portion of an image carrying beam therethrough and onto a photoconductor. Output signals from the photoconductor are indicative of the degree of image clarity of the light incident thereto and these signals are passed to signal detector circuits wherein the signal resulting from light passing through the first section of the disk are compared with those signals resulting from light passing through the second section. The comparison of these signals is indicative of the degree of focus of the light beam and an error signal corresponding thereto is created from the outputs of the signal detector circuit.