| 摘要 |
It is an object of the present invention to perform displacement measurement that has a simple configuration allowing for reduction in size, that is not affected by inclination accuracy of optical elements or by positional variations of a diffraction grating in a surface direction, and that enables an adjustment of the optical resolution. A laser beam 13 from a laser light source 12 is turned into parallel light 15 by a collimator lens 14. The parallel light 15 is divided by a first diffraction grating 16 into direct light and diffracted light, which respectively pass through a second diffraction grating 18 on a movable side that faces the first diffraction grating 16. The diffracted light that follows the optical axis of diffracted light of a prescribed order from the first diffraction grating 16, including the diffracted light that is diffracted by the second diffraction grating 18, is received by an optical sensor 20, and the light amount thereof is detected. The displacement of the parallel light in the optical axis direction is measured from an interference pattern corresponding to the amount of movement of the second diffraction grating 18, or a signal thereof. As a result, the displacement measurement that has a simple configuration allowing for reduction in size, that is not affected by inclination accuracy of optical elements or by positional variations, and that enables an adjustment of the optical resolution can be performed. |
