| 摘要 |
PURPOSE:To attain ease of optical axis adjustment by using a detection section to detect the presence of a carrier signal from a limiter amplifier, comparing the result at a comparator, activating a drive section with its output signal and lighting a display light emitting element. CONSTITUTION:An optical modulation signal 19 incident in a photodetector 1 is converted into an electric signal by the photodetector 1 when optical axes are matched and the signal is amplified by a preamplifier section 2. The amplified signal is selected by a band pass filter 3 and amplified by an amplifier section 4 and a limiter amplifier 5. Since the output of the amplifier 5 is detected for the carrier by a detection section 7, the output of the detection section 7 goes to a high level, the level is compared with a predetermined reference level by a comparison section 8 to activate a drive section 9. Thus, a display light emitting element 10 is lighted to notice the matching of optical axes. |
