| 摘要 |
PURPOSE:To obtain a stable pulse signal for position detecting, by extracting the raster scan light of a cathode-ray tube in the form of two-divided beams and then extracting the difference between a signal received a photoelectric conversion and the other signal received a photoelectric conversion through the blue and green filters. CONSTITUTION:The raster scan light on a screen of a cathode-ray tube 1 is detected at an end 21 of a photodetecting means 2 and then divided into two beams to be led to other terminals 22 and 23. The light made incident from the end 22 is converted into an analog electric signal through a photoelectric converting circuit 4 to be supplied to a negative terminal of a differential amplifier 6. The incident light from the end 23 is passed through an optical filter 3 of blue and green, and the blue and green beams are converted into the analog electric signals through a photoelectric converting circuit 5 to be supplied to a positive terminal of the amplifier 6. Coincidence is secured between the conversion coefficient of the circuit 4 and that of the circuit 5 including the filter 3. Thus only the red signal is obtained at an output terminal 7 of the amplifier 6; while the blue and green signals are obtained at a terminal 8. Both signals are shaped into the pulselike waveforms and mixed up to obtain a stable position detecting pulse signal regardless of the color of light emitted from the tube 1. |
