| 摘要 |
PURPOSE:To obtain an optical scale reading apparatus simple in constitution, good in operability and having ultra-high resolving power, by a mechanism that a reflective type scale is used as a scale and laser beam incident to the scale is enlarged while 90 deg.-phase difference is formed by utilizing beam phase delay by the reflection of a half mirror. CONSTITUTION:The output beam of a semiconductor laser 21 is incident to a scale 23 through a lens 22. + or - primary diffraction beams are reflected by mirrors 24, 25 and, after passed through a half mirror 26, mixed and interfered by a second half mirror 27. The beams from the mirror 27 are converted to electric signals by light receiving elements 28, 29. The phase difference of the signals at the light receiving elements 28, 29 is determined only by the phase delay by the reflections of - primary diffraction beam and + primary diffraction beam at the half mirror 27 while the phase delay is determined by the incident angle of the incident beam and the angle of a polarization surface. When the polarization surface is parallel to the incident surface, the incident angle is 75 deg. while the outputs of the elements 28, 29 come to sine waves having phase difference of 90 deg. and, by analogue interpolation, ultra-high resolving power is obtained. |
