| 摘要 |
A light modulation type photointerrupter of the present invention includes: a light source that emits a light pulse to a transit area where an object transits; a driving circuit that drives the light source to emit the light pulse; a photoreceptor that converts the light pulse from the transit area into a pulse current and outputs the pulse current; an integrating circuit that integrates a pulse signal resulting from the pulse current and outputs a result of the integration, the integrating circuit having different time constants at a rise and at a fall of the pulse signal; and a detecting circuit that detects, based upon the output from the integrating circuit, presence or absence of the object in the transit area. In the above structure, the light source is driven to emit a pulse. This reduces the loss of power in the light emitter and the consumption of the current. Moreover, the object can be detected by using a simply structured integrating circuit. Therefore, cost can be reduced.
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