Moir? Separations

The analysis of the moir? phenomenon by means of elementarygeometry which was begun by Firby (1984) and Firby & Stone(1984) is extended from first order to all integral and fractionalorders, and from consideration of the plane only to considerationof a general finite-dimensional space . The idea of the -curve, which forms the boundaryof the set in in which first-order interference might be observed, is extended to the idea of aboundary in for any given integral or fractional order of interference. Separating setsin , which form the boundary of regions in which two given integral or fractional ordersof interference might dominate relative to one another, areintroduced. The wavelength and contrast analysis previouslycarried out only for first-order interference in is extended to deal with all integral and fractionalorders of interference, and this is used to explain why highintegral orders, and all fractional orders, of interferenceare observed only in exceptional circumstances.