Focussing correction servo-mechanism for photographic optics - uses microprocessor to determine luminous increments from pairs of sensor elements to drive servomotor

摘要

The device has a tube, in an optical system which contains an objective lens centred on an optical axis. A lens, movable along the axis, displaces the image plane to maintain the lines of a sight in focus. This image is directed by a semireflecting mirror onto luminous detectors perpendicular to each other to measure the flux from the sight lines. These signals are applied by A-D converters to a microprocessor. The microprocessor determines differences or increments from each pair of sensor elements. From the amplitude and the sign of the difference of the sum of the detector signals the microprocessor controls a servomotor via a D-A converter to null the signal and maintain the image in focus. The system is suitable for, e.g., a submarine periscope.