| 摘要 |
PURPOSE:To reduce the collector current of a transistor for amplifying the signal photoelectric current. CONSTITUTION:When a stationary photoelectric current drawing circuit C is operated, all the stationary photoelectric current from a light receiving element 1 is drawn to a transistor Tr1. When a variable-luminescence level circuit B is operated, a light emitting element 3 is illuminated, the light collides with an object alpha, and the reflected light is received by the light receiving element 1. The stationary photoelectric current is still drawn to the transistor Tr1 by the operation of the stationary photoelectric current drawing circuit C, thus the signal photoelectric current containing the information such as the distance to the object alpha is guided to a signal processing circuit A. The signal photoelectric current is amplified by a transistor Tr5, logarithmically compressed by a compression diode D1, and converted into voltage. The luminescence level of the light emitting element 3 is changed in response to the collector voltage of the transistor Tr5 by the variable-luminescence level circuit B, the level of the light colliding with the light receiving element 1 is changed, and the level of the signal photoelectric current of the light receiving element 1 is changed accordingly. |
