High-performance absolute rotary encoder using multitrack and M-code

We describe the development of a high-resolution absolute optical encoder that achieves a resolution of 4,194,304 division/rev (22 bits) at a diameter of 34 mm, based on a new angle detection principle in which the two sets of interpolation data from two differing cycles by multitrack and M-code (maximum length sequence) data are combined. This absolute encoder also achieves an accuracy of 20 arcsec (16 bits) to minimize the sinusoid wave distortion of the signal from the photodetector.