| 摘要 |
<p>PURPOSE:To maintain linearity for a detecting circuit and to enable adjustment in a range, in which there is no distortion, by providing a means, which switches the luminous intensity of a light emitting element to normal intensity and suitably attenuated intensity, in a light emitting system. CONSTITUTION:When a detection level is adjusted in a light receiving side, a changeover switch 4 is opened and a transistor 3 is turned OFF. Then, a current to be supplied to a light emitting diode 14 is decreased by serial resis tance between a dipping resistor 2 and a resistor 13. Thus, light radiating from the light emitting diode 14 can be reduced. A semi-fixed resistor 7 in the light receiving side is adjusted and detection sensitivity is adjusted. At such a time, since the light itself from the light emitting diode 14 is dipped, the detecting circuit maintains the linearity and the adjustment can be executed in the range not to generate the distortion. On the other hand, in the case excepting for the adjustment, the switch 4 is turned ON and the transistor 3 is turned ON. Then, the resistor 2 is by-passed.</p> |
