JP2971493B

PURPOSE:To ensure the long life of a semiconductor laser by emitting laser light continuously for a definite period of time when the laser light emitted intermittently is detected. CONSTITUTION:An intermittent light emission driving means 3 makes the laser light emitted intermittently from a laser light generating means 1. Besides, a continuous emission driving means 4 has a function to make the laser light emitted continuously for a definite period of time when a reflected light detecting means 2 detects the reflected light of the laser light emitted intermittently, namely, when it detects an article. Then, the presence of the article can be detected by using the semiconductor laser and the detecting means 2 without providing any additional article detecting device, and the semiconductor laser emits the light continuously only when the article is detected, and is lighted only intermittently during another period. When the light emitting time of the semiconductor laser is made short practically, the life of the semiconductor laser can be lengthened.