Angular Deviation Measuring Device and Its Method of Use.
U S Pat 3 864 043 1975 Feb; :
There is described a high-resolution measuring device and its method of use that utilizes a spatially modulated beam, like a laser beam, to determine orientation deviations of a device. The angular deviations are determined by comparing prior preestablished standards for specific orientation settings with subsequent readings for the same settings. A reference phase detector determines the modulation intensity phase for both readings. Thereafter, a reference mask with a second detector detects the intensity of the beam after it is reflected from the device. A phase meter then compares these two detector readings for each angular device orientation. By comparing different sets of readings for the same specific orientations, variations for correction purposes may be noted.
U.S. Pat. 3,864,043, Feb. 4, 1975, Chem. Abstr. Not Found