Large optics gimbal mounts

Abstract

Angle encoder calibration is needed to improve the accuracy of rotary position feedback in manufacturing equipment. Although several self-checking methods have been developed, the fundamental problem of calibrating angle encoders remains unsolved. Existing methods require an encoder to be calibrated on specially designed angle comparators, but the process of transferring the encoder from the comparator to the encoder's application axis typically introduces arc-sec level error. This paper presents the Time-measurement Dynamic Reversal (TDR) method to calibrate encoders on their application axes. The TDR method has demonstrated 0.006 arc-sec uncertainty (2σ), including the first 500 harmonic components.