| 摘要 |
PROBLEM TO BE SOLVED: To provide a photoelectric encoder in which unwanted harmonic components from an optical grating are not detected, and only the fundamental spatial frequency caused by constant intervals of the optical grating is detected, so that position measurement is stabilized and measurement position accuracy can be improved. SOLUTION: A photoelectric encoder 100 in which light R1 emitted from a light source 102 is modulated by an optical grating 110 of a scale 106 and the modulated light R3 is detected by a light receiving element 122 includes a one-side telecentric optical system 114 which forms an image of the light R3 modulated by the optical grating 110. The one-side telecentric optical system 114 has an aperture 118A through which part of the light R3 modulated by the optical grating 110 is transmitted, the aperture having a size which is required when a cutoff spatial frequency fc1 that is a spatial frequency indicating a resolution limit of the one-side telecentric optical system 114 caused by the light R1 emitted from the light source 102 has a value between the fundamental spatial frequency Sf1 of the optical grating 110 obtained by Fourier transformation and the double harmonic Sf2 of the fundamental spatial frequency Sf1. COPYRIGHT: (C)2011,JPO&INPIT |
