Edge detecting device in optical measuring instrument

摘要

An edge detecting device in an optical measuring instrument for detecting a transmitted or a reflected light to directly or indirectly measure a dimension of an object to be measured is disclosed. The edge detecting device comprises A sensor including two light receiving elements disposed coaxially with each other and the two light receiving elements so as to produce phase shift signals in response to a bright or a dark portion during the relative movement. Levels of sensor output signals appearing at sensor output terminals in response to outputs of the light receiving elements become equal in value to each other each time the bright or dark portion is generated during the relative movement. A difference calculator is connected to the sensor output terminals, for calculating a difference between the phase shift signals; A region signal generator making at least one output signal taken out of a signal processing system extending from the output side of the sensor to the input side of the difference calculator into an input signal, is provided for outputting a signal in a specific region including a cross point with a reference level signal of the phase shift signals. Sensing means for outputting a cross signal between an output signal from the difference calculator and a preset reference level signal while the region signal genertor outputs the signal is also provided.