| 摘要 |
PURPOSE:To eliminate the need for assembly adjustments, to obtain tolerance to disturbance, and to constitute a small-sized, lightweight length measuring instrument with high accuracy by integrating principal parts except a diffraction grating as a reference scale on one substrate. CONSTITUTION:A length measurement optical system consists of a light source LD, a collimator lens CL, beam splitter HM1 and HM2, phase difference plates EP1 and EP2, corner cube prisms CC1 and CC2, a polarization beam splitter BS, photodetectors PD1 and PD2, an objective LN, an optical position detector PS, etc., which are integrated on one substrate. Light emitted by the light source LD passes through the length measurement optical system and diffraction grating GS and is detected by the photodetectors PD1 and PD2. The outputs of the photodetectors PD1 and PD2 are counted to measure the quantity of relative movement between the length measuring head MH and diffraction grating GS. |
