COMBINING INTERFERENCE FRINGE PATTERNS TO A MOIRE FRINGE PATTERN

摘要

An interferometer (1) is arranged to form a first interference fringe patter n comprising at least ten interference fringes; recording an image of said fir st interference fringe pattern; perturbing an optical path in the interferomete r (1) to form a second interference fringe pattern comprising at least ten interference fringes; and combining an image of said second interference fringe pattern with the recorded image of the first interference fringe pattern to produce a further image comprising a moiré fringe pattern arising from a difference or differences between the first and second interference fringe patterns. The combining step involves subtraction (4) of digital images. Different wavelengths and interferometers are used: Michelson, Mach- Zehnder, Fizeau, Twyman-Green. In this new approach, all the errors of a poo r quality, misaligned system are accepted and then eliminated by the combinati on process, producing a moiré fringe pattern. The method enables very large aperture optical systems for traditional and engineering interferometers to be constructed from inexpensive and basic components.