AUTOMATIC FOCUSSING SYSTEM FOR AN OPTICAL SYSTEM

Assignee

EMI LIMITED, A COMPANY OF GREAT BRITAIN

Filed

Dec 3, 1981

Granted

Mar 28, 1989

Location

SURREY GB

Abstract

A focussing system in which a detection and processing device (2) scans the image plane, in raster fashion, to generate a video signal representing the intensity of radiation prevailing at successively scanned locations. A selection circuit (6) contains a programmable memory which generates addresses suitable for selecting discrete sets (S) of neighbouring locations and a circuit (7) is responsive to the addresses to access to a processing circuit (8) only those portions of the video signal which correspond to the sets (S) of locations. The processing circuit (8) generates difference signals representing differences of intensity between neighbouring locations and evaluates the number (Ptm) of difference signals exceeding each of a number of preset threshold values (tm) to generate a histogram. The numbers constituting the histogram are then weighted and scanned to generate a control signal (F) representing the focus.

Source: Google Patents