| 摘要 |
PURPOSE:To discriminate whether an abnormality is caused by abnormality of a photodetecting element or the abnormality of a light emitting element where the ON/OFF state of the photodetecting element is not equal to an estimated state by detecting said ON/OFF state. CONSTITUTION:It is supposed that an LED 11 which should be kept ON is turned off owing to the abnormality either of the LED 11 or a phototransistor PHT 21 in a state where the optical path of an infrared ray L1 is cut off. Under such conditions, an LED 12, for example, that possibly turns on the PHT 21 is turned on and at the same time the state of the PHT 21 is checked. If the PHT 21 is kept OFF, it is decided that the LED 11 is normal and the PHT 21 is broken. While it is decided that the LED 11 is broken and the PHT 21 is normal if the PHT 21 is turned on. The lighting control and the abnormality judgement of the LED are carried out by the microcomputer of a control part 3. |
