| 摘要 |
PURPOSE:To detect an accurate position, by inputting outputs of two photodetectors to a differential amplifier to amplify them differentially so that the variance of the magnitude of an output signal is suppressed. CONSTITUTION:A rotary slip plate 4a, which has one or more slit rows and can be operated from the external, and two fixed slit plates 4g and 4h which have one or more slit rows respectively and are arranged in positions point-symmetrical with respect to a revolving shaft 4b are provided between two pairs of light emitting elements 4c and 4e and photodetectors 4d and 4f facing each other respectively. Outputs of two photodetectors 4d and 4f are inputted to the differential amplifier (which is not shown in Fig.) and are amplified differentially so that the variance of the magnitude of the output signal is suppressed. Since a distortionless output signal is attained even if light emitting elements 4c and 4e are degraded and the rotative velocity is changed, an accurate position is detected. |
