JPH0335603B

PURPOSE:To attempt rough detection of a position of a body or a distance to the body, by detecting the body, only when it is located in a narrow detecting range. CONSTITUTION:A light-flasher contains light-sources 11, 12 irradiating a speciment alternately and by changing each angle of sight, the optical axies are intersected. further, a light-receiver 13 is arranged in such a way that it is oriented perpendicular to a reflecting surface of a specimen. And, a change- over switch 16, upon input of a clock.pulse PT, supplies an electric current to the source 11 in its low level and to the source 12 in its high level. A signal distributor 17 introduces this pulse PT to act and supplies the output signal of the light receiver 13 caused by an incident beam of the source 11 to an integrator 18 at low level and the output signal of the light receiver 13 caused by an incident beam of the source 12 to an integrator 19 at high level. And, the outputs of the integrators 18 and 19 are compared 20. From the output condition of the comparator 20 position or distance of the specimen is identified.