COMBINING INTERFERENCE FRINGE PATTERNS TO A MOIRE FRINGE PATTERN

摘要

An interferometer (1) is arranged to form a firstinterference fringe pattern comprising at least ten interferencefringes; recording an image of said first interferencefringe pattern; perturbing an optical path in the interferometer(1) to form a second interference fringe pattern comprisingat least ten interference fringes; and combining animage of said second interference fringe pattern with therecorded image of the first interference fringe pattern toproduce a further image comprising a moiré fringe patternarising from a difference or differences between the firstand second interference fringe patterns. The combiningstep involves subtraction (4) of digital images. Differentwavelengths and interferometers are used: Michelson,Mach-Zehnder, Fizeau, Twyman-Green. In this new approach,all the errors of a poor quality, misaligned systemare accepted and then eliminated by the combinationprocess, producing a moiré fringe pattern. The methodenables very large aperture optical systems for traditionaland engineering interferometers to be constructed frominexpensive and basic components.