| 摘要 |
PURPOSE:To take an accurate measurement of displacement while a discharge lamp is turned on by providing a light servo circuit which has a high-voltage generation part whose response frequency is higher than the commercial frequency. CONSTITUTION:A high-voltage power source 17 which makes a fast response, the light servo circuit 18, and an amplifier 19 for light servo matching are arranged so as to receive and amplify the output of a time-division switch 8 to a proper level and then control a high voltage with the output. Those light servo system and power source 17 are employed to compensate variation in the brightness on the surface of a target 1, and an accurate measurement of displacement is taken in the presence of disturbing light which varies abruptly. |
