Method of and device for the photoelectric control of length-ruling and length-measuring machines

摘要

1,147,467. Photo-electric length measurement using radiation interferences. CARL ZEISS JENA VEB. May 26, 1966, No.23587/66. Heading G1A. In a machine which rules or measures lengths by photo-electrically scanning radiation interferences the source of radiation is tuned to a wavelength which is an integral fraction of a statutory unit of length; the desired wavelength may be produced by an interferometric or beat-frequency comparison with a standard wavelength radiation source. Two interference plates 2 are fixed to the bed and slide of the machine respectively and as the slide moves the interferences are counted by a photo-electric receiver 3 and counter 4 as a measure of the slide's movement. The source of radiation which is a laser, is compared with a standard krypton source 8 by an interferometer system 10, comprising two inter-connected Fabry-Perot interferometers, which automatically tunes the laser to the desired wavelength. Tuning may be effected by adjusting the pressure of the laser. Alternatively one laser may be tuned to the standard source and a second laser tuned to the desired wavelength by noting the beat-frequency of the pair.