| 摘要 |
PROBLEM TO BE SOLVED: To accurately and efficiently detect a zero-point position signal regarding a rotary object even if a rotary mechanism has a backlash or has fallen when measuring the rotary state of the rotary object to be inspected. SOLUTION: Luminous flux from a laser diode light source 11 of a rotary encoder becomes parallel luminous flux I1 by a collimator lens 12, and the luminous flux 11 is partially reflected by a half mirror 13 and enters a zero- point detection part Z of a rotary disk 14 that rotates with a rotary axis 14a as a center as zero-point detection luminous flux I2. When the rotary disk 14 is rotated and a linear diffraction grating 14c for detecting a zero point reaches the position of the zero-point detection part Z, and then the zero-point detection luminous flux I2 enters the diffraction grating 14c, first-order diffraction luminous flux I3 is emitted and is condensed on a circumference at a specific distance from a light axis O of a zero-point detection optical system at the focusing position of a condensation lens 15. By detecting the differential signal of the output signal of photodetectors 16a and 16b, the zero point can be accurately detected without being affected by the deviation or fall of the shaft of the rotary disk 14.
|
