Automatic focussing system with light-sensitive CCD elements - compares illumination differences to form difference signal for controlling motor assigned to lens

摘要

The automatic focusing arrangement depends on light-sensitive c.c.d.s. Two image planes are produced conjugated with the image plane. Each c.c.d. is to one of the conjugated image planes. In the correctly focused state both c.c.d.s. deliver equal signals. In out-of-focus condition one c.c.d. delivers a greater signal than the second one when the image plane liesin front of the focused plane, but the other c.c.d. delivers a greater signal than the first one when the image plane lies behind the focused plane. The sum of the illumination differences between neighbouring elements of one c.c.d. is compared with the sum of those of the second c.c.d.