Camera automatic focussing control with exposure light scanner - has electro-optical transducer for moving raster simulation, acting as light modulator

摘要

The electro-optical transducer for an automatic focus control of a camera has an array of electrodes on one side of a transparent plate (1) and a corresponding array on the other side. The electrodes are arranged to control the spatial transparency of the plate and scan the image focussed on the plate, line by line. The plate contains a liquid crystal which can be made transparent in clearly defined strips. The relation of the spatial scan with the time dependent variation of transmitted amplitude is a measure of the degree of focus. A feedback control for the focus setting optimises the measured signal to a maximum for fine focus. No moving components are required for the monitor circuit and detector.