| 摘要 |
PURPOSE:To enable the detection of displacement of a diffraction grating, by detecting the difference in the optical path length between two beams to adjust the length of the optical path. CONSTITUTION:Light emitted from a multimode semiconductor 1 is made incident into a beam splitter 2 to be divided in two, one toward B of a diffraction grating 3 and the other toward C thereof at A. The light beams incident into the diffraction grating 3 are each diffracted to be made incident into mirrors 5 and 6 through lambda/4 plates 4 and 7 and reflected at D and E to be made incident into the diffraction grating 3 again. The respective beams thus rediffracted with the diffraction grating 3 return to the beam splitter 2 to be interfered with each other and then, made incident into photo detectors 10 and 11 through a half-mirror 8 to detect the intensity of the interference. In this manner, the displacement of the diffraction grating 3 used as scale is measured thereby enabling the adjusting of the optical path length easily and at a high accuracy. |
