PROCESS FOR POSITIONING A LIGHT BEAM ON A PICTURE AREA

摘要

A method of positioning a light beam on a picture surface relative to a light sensor located on the picture surface includes the step of completely illuminating the sensor with the light beam while the sensor is exposed to ambient light and recording a first output signal. A second output signal is recorded when the sensor is exposed to only ambient light. The first and second output signals are provided to an evaluation circuit to calculate a positioning signal having a value equal to a selected percentage of the difference between the first and second output signals. The light beam is positioned relative to the sensor to expose the sensor to a percentage of the light beam which is equal to the selected percentage of the difference between the first and second signals