| 摘要 |
<p>When an incident light is obliquely incident on index scale 20, the optical path length of light A becomes longer than the optical path length of light B and an optical path length difference occurs, which causes a phase difference in both of the diffracted lights incident on photodetection element 26. According to the phase difference, intensity of a photoelectric detection signal output from photodetection element 26 changes. That is, due to a periodic change in the incident angle of the incident light, the phase difference between light A and light B is modulated, and the interference signal becomes greatly modulated.</p> |
