A Moiré Fringe Method of Fabry-Perot Spectrometer Scanning

An aperture system is described which executes a spectral scan for a Fabry-Perot spectrometer. Overlapping Fabry-Perot patterns produce straight-line moiré fringes; hence, a linear ruling placed over a Fabry-Perot pattern generates a second, displaced Fabry-Perot pattern, consisting of segments of the rings of the first pattern. The segmented rings expand or contract as the ruling is moved past the mask. The result is a wavelength scan, and the system can therefore be used as a Fabry-Perot spectrometer. The theory is developed, the results of a preliminary application described, and an indication of some possible applications given.