METHOD AND APPARATUS FOR MEASURING INTERFEROMETER FRINGE PATTERNS

摘要

Method and apparatus for accurate automatic measurement of fringe pattern shift in an optical interferometer. Fringe patterns from an interferometer are imaged upon the photosensitive target of a television camera with fringe line patterns parallel to horizontal scanning lines or scanning raster of the TV camera. Scan line video signals from the camera are integrated and intensity detected to produce a corresponding binary fringe signal for controlling a bistable circuit which is caused to be in one or the other of its stable states according to whether the video signal from the TV camera is above or below, respectively, a selected threshold level, e.g. presence or absence of an interference fringe line during a line scan. Counters count the number of scanning lines occuring during the time the bistable circuit is in each of its states, respectively. Thus, the scanning lines between fringes as well as those covered by each fringe can be counted for as many fringes as necessary to determine fringe positions. The center of a fringe may be located by dividing the number of scanning lines per fringe by two. Consult the specification for further features and details.