PROCEDE ET DISPOSITIF PHOTOELECTRIQUES DE CONTROLE

摘要

1401699 Photo-electric measurement K DRYCZYNSKI 6 Nov 1972 [4 Nov 1971] 51074/72 Heading G1A In a photo-electric measuring arrangement in which the measurement is effected by applying intensity modulated light to the object to be investigated and separating a component of the same frequency from the detector output, the working, point of the photo-detector is maintained constant by applying an auxiliary source of light to the photo-detector and controlling the intensity of the auxiliary light by way of the direct voltage component in the photo-detector output to keep ambient and auxiliary light incident thereon constant. The auxiliary light may be applied directly or indirectly, and the variation may be by source variation or by control of an iris shutter or a wedge in the light path. Phase sensitive rectification is used in the main measuring system using pulses developed synchronously with chopping by electromagnetic or photo-electric means or in the case where the source e.g. a light emitting diode is energized by an oscillator the oscillator is coupled to the rectifier. The main measuring system may use light guides and the value may be indicated or used for control. The system may be used for maintaining a desired distance between workpieces or rollers which may obstruct the light or for the investigation of surface properties.