OPTICAL POSITION MEASURING INSTRUMENT

Japanese Patent JPH0346508

A

PURPOSE:To execute the measurement with high precision even with respect to an object in which a surface reflection state is fluctuated greatly by deriving an added value of plural signals amplified by an amplifying means and the maximum value, and adjusting the light quantity of a light beam and the amplification gain, based on these values. CONSTITUTION:An arithmetic circuit 15 inputs voltage signals V1, V2 from sample and hold circuits 9a, 9b every time of a pulse driving period of a light source driving circuit 14. At the time of V1+V2Vh (a decided value for increasing/ decreasing the light emittion quantity and the gain > Vd1), it advances to a decrease of the light emission quantity. Also, when the present light quantity value L is LVd2 (the lower limit value corresponding to the minimum photodetecting quantity < Vd1), the control is ended as it is, and at the time of V1+V2