| 摘要 |
PURPOSE:To improve the speed of response to the detection of a transfer material by providing a light source and a light receiver, and by providing further a second light source irradiating the light receiver constantly irrespective of the presence or absence of an object interrupting a light from the light source when the presence or absence thereof is detected. CONSTITUTION:An output of a CdS light receiver 1 and a reference voltage divided by a resistor R are supplied to a comparator 2. When a light from a light source 3 is interrupted, an output of the comparator 2 is inverted, and thereby the presence of a transfer material is detected. On the occasion, part of the light from the lamp 3 is guided onto the side of the CdS light receiver 1 through an optical fiber 4 so that a light in a quantity of 1/10 of the quantity of the light under the condition of the absence of the transfer material is emitted constantly irrespective of the presence or absence of the transfer material. Accordingly, even when the light is emitted abruptly immediately after it is interrupted, the resistance value of the light receiver 1 can be lowered rapidly to detect the absence of the transfer material, and thus the speed of response thereof can be improved sharply. |
