| 摘要 |
<p>PURPOSE: To detect the occurrence of abnormality and the cause and position of the abnormality by providing a comparison means of the output level of a photosensitive diode and a standard signal level. CONSTITUTION: Currents I1, 12 corresponding to a light radiating position and a light amount are output from both ends A1, A2 of a photosensitive diode (PSD) 3. The currents I1, 12 are converted into voltages by the current-voltage converters 41, 42 in a sensor output portion 4. Converted outputs are input to a differential amplifier 43 so as to output the voltage proportional to the difference of the output currents I1, 12. The sensor outputs are sent to an arithmetic processing unit so as to obtain a light radiation position. The outputs of the converters 41, 42 are sent to an adder 51 in a feedback portion 5, and the brightness of an LED 2 is adjusted so that a current sum (I1+I2) becomes constant. Since the voltage of a point B becomes 0V when the LED 2 is broken down, a high level signal is output from an output terminal T11 at an abnormal time by comparing the same with a standard voltage VR2 through a comparator (a comparison means) 11.</p> |
