PURPOSE: To obtain an optical displacement measuring apparatus wherein, at a point in time when an abnormality is caused, a measured value at the point in time is held without delay.
CONSTITUTION: A light-emitting element 11 forms a light-projected spot on the surface of an object, and a position detection element 14 outputs one pair of position signals I1, I2 in which the ratio of output levels is decided so as to correspond to the position of a photodetected spot. An error amplifier 29 finds a difference between the amount of photodetected light found by adding the position signals I1, I2 in an adder 26 and a prescribed reference value. On the basis of the output of an integrator 23 integrating the difference, the amount of emitted light of the light-emitting element 11 is fed back and controlled. A subtracter 25 finds a difference between the position signals I1, I2, and outputs the difference as a value proportional to a displacement. When a hold signal is input through a logic circuit 33, a sample-and-hold circuit 30 holds the output value of the subtracter 25 at its point in time. On the basis of the output of the error amplifier 29, the logic circuit 33 detects that an abnormality has been caused.
KAMIYA ATSUSHI
TAKADA YUJI
