The collimation degree of the light beam of LED exerts a tremendous influence to the performance of optical encoder. Through analyzing the impact that the radiation angle of light source has on flux

and applying of Rotation matrix and frequency-domain solution

authors have lead to moiré patterns’ light distribution function as well as its simulation waveform with various slit width. Furthermore

they analyze the influence of collimated light source to the contrast ration of moiré patterns and the max gap of grating

whose result shows the identity with the simulation waveform. Therefore

this paper is very helpful to the design and the production of the high quality encoder.