Compensation of moire fringe sinusoidal deviation in photoelectrical encoder based on tunable filter

In order to improve the precision of the absolute photoelectrical encoder, a compensating method is put forward, which restrains the harmonics in moiré fringe signal. After analyzing the relationship between the subdividing error and the sinusoidal index, a low-pass digital filter which can make the moiré signal satisfy the need of 1024 subdivision is designed. Considering with the fundamental frequency varies with the rotating speed of encoder, the tunable filter is adopted, whose cutoff frequency is calculated according to the coarse information of the encoder. The simulating results show that the proposed method can improve the sinusoidal index, especially at high rotating speed. At last, the compensating algorithm is implemented in the terminal of satellite optical communication, which needs high resolution. The experimental results show indicate that the developed method is feasible.