| 摘要 |
PURPOSE:To prevent the reflection factor of a mirror from unnecessarily lowering and varying, by providing a logarithmic amplifying characteristic to an amplifier for amplifying the output of a photosensor. CONSTITUTION:The outputs of photosensors 1, 2 are amplified by current amplifiers 10, 12, respectively, and are turned into voltages having several hundred mV. Since these voltages are ready to saturate if they are directly amplified, the next stage amplifiers 11, 13 are applied with negative feed-backs through diodes 14, 16. The current-voltage characteristic of the diodes may exhibit a logarithmic function, and therefore due to the feed-backs from the diodes the amplifying characteristics of the amplifiers 11, 13 become logarithmic. Further, the photosensor 1 detects light from the rear of the vehicle, and the photosensor 2 detects the brightness of the surroundings of the vehicle. With this arrangement the amplifiers will not saturate even upon relatively bright time such as, for example, evening, and therefore, the reflection factor of a mirror will not vary, frequently. |
