| 摘要 |
A laser interferometer 10 uses light divided into reference beam 14 and test beam 15 traveling different paths from which beams 14 and 15 are reflected and recombined for detecting interference fringes. The path for test beam 15 is arranged to change in length with deviation transverse to its path. To do this, a reflective diffraction grating 25 is inclined relative to test beam 15 at the autocollimation angle of the grating to reflect the test beam back on itself from the inclined surface of the grating. Then transverse deviation of the region where test beam 15 is incident on grating 25 changes the path length of the test beam reflected from the inclined surface of the grating and allows a measurement.
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