Length standard comparison method and apparatus utilizing holographic interferrometry

摘要

A hologram of a wave front reflected by the end of a primary standard, either produced by exposure of a plate in the apparatus or synthesized by computer, is illuminated by a laser with a direct beam and with a beam reflected from the end of a standard to be measured mounted in a reference position. Interference fringes are produced on a screen and the standard to be measured is moved from a reference position to a position in which the reflected wave front coincides with the wave front recorded by the hologram while the fringes are counted to determine the difference in length.