| 摘要 |
PROBLEM TO BE SOLVED: To provide a relative position detector using diffraction light. SOLUTION: The light from a source 1 is projected to a scale 2 and the image of the scale is projected to light reception elements 3, 4, etc., and the relative position of the scale 2 is detected from the output change. On a mask arranged on a receiving optics element or in front of the receiving optics, optical system dimensions are set so that the scale pitch of the scale image by diffraction light is the same as the scale pitch of the scale image by the light not diffraction light and the phases coincide to eliminate the effects of diffraction. The widths of the reflection part and transmission part are made different and the scale pitch of the scale image by diffraction light not diffraction light is the same as the scale pitch of the scale image by the diffraction light and the optical system dimensions are set so that the phase shifts by 180 degrees to double the resolution. And the dimensions are set so that the phase shifts by 120 degrees to triple the resolution. Also, by using up to±secondary light, the phases of images of diffraction light and of light not diffraction light are shifted by 174 to obtain two position detection signals with different phases.
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