DISTANCE SENSOR

PROBLEM TO BE SOLVED: To reduce costs and to improve or maintain measurement accuracy by suppressing frequency bands of signals to be processed by a simple configuration in a distance sensor.SOLUTION: A distance sensor 1 includes: first, second synthesizers 11, 12 which generate signals with first, second frequencies; a sample-hold circuit 3 which samples the signal with the first frequency with the second frequency to output a start signal; a floodlight 4 which transmits a signal wave made into pulses with the first frequency; an optical receiver 5 which receives the signal wave to be reflected and returned to output the received signal; a comparison determination circuit 6 which generates a stop signal based on a signal obtained by performing sample hold to the received signal with the second frequency to be output; and a counting arithmetic unit 7 which calculates distance to an object M based on elapsed time from output of the start signal to output of the stop signal. By the comparison determination circuit 6, a low speed operation of a system is allowed by equivalent sampling and the sample hold.