High-Precision Absolute Rotary Angular Measurement by Using a Multielectrode Circular Position-Sensitive Detector

We propose a multielectrode circular position-sensitive device that does not have any discontinuity in the detection region and has multiple electrodes for current output. We have also manufactured a prototype device. The device has a circular detection region that consists of photodiodes radially aligned with regular pitch and a resistance line connecting the outer edges of the photodiodes. All of the photocurrent excited in the photodiodes flows into the resistance line and is extracted from the electrodes connected to the resistance line at even intervals. There is no insensitive region for current output in this device since the detection region and the resistance line are separated; thus, detection with high resolution is possible at every angular position. We conducted a simulation of the detection characteristics and will propose a computational method for the position that uses four-electrode outputs in this paper. We confirmed that it is effective in minimizing the error from both the simulation and the experiment. We will also propose a measurement system of absolute angle using this method, confirming an error of less than 0.1° in the computation results.