RANGE FINDER

PROBLEM TO BE SOLVED: To provide a range finder in which an erroneous detection caused by noise from a converter is prevented without increasing size of the range finder and cost. SOLUTION: With regard to a measuring period for emitting and receiving a laser beam, the pulse signal of the control IC 8 of a DC/DC converter 8 is disabled by turning-on of a switch circuit 8b, since switching operation of a transistor Tr1 is stopped, electromagnetic noise accompanying the switching operation is not erroneously detected, a time from an emission to a reception can be accurately counted, a distance up to a preceding vehicle can be accurately found. The constitution is made possible only by providing the simple switch circuit 8b, increase in the circuit is hardly performed, and almost no increase in size of the range finder and cost is accompanied.