Ultra-Precision Angle Sensor Using Critical Prisms and Its Self-Calibration System

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An angle sensor based on the steep variation of reflectivity in neighborhood of the critical angle has been constructed. In order to reduce the influence of the direction angle fluctuation of the optical source due to thermal drift, a compensating receiving part has been added. Two angle sensors of this type have been developed, which have a measuring range of 1800 s (arc) and resolution better than 1/s (arc). A new self-calibration system of ultra-precision angle sensor which could not be calibrated with any reference sensor has been proposed and constructed. The developed system is able to calibrate not only the average sensitivity but also the linearity error (deviation from the average sensitivity line). It was found that the repeatability error of the calibrated mean sensitivity was 0.01%, and the repeatability error of the calibrated linearity error was 0.025 s(arc). Moreover the direction angle fluctuation due to the thermal drift of the light source was suppressed to be about 1/ with the effect of compensation part.