Abstract: A scanning interferometer employs dual interferometer modules at different wavelengths to expand a dynamic range of measurement, a compound probe for measuring multiple surfaces, and a confocal optical system for distinguishing between the surfaces measured by the compound probe. Within the compound probe, miniature optics divide a test beam into two sub-test beams that are focused normal to different test surfaces. Both sub-test beams contain the different wavelengths. A separate interferometer monitors movements of the compound probe for producing absolute measures of the test surfaces.

Abstract: Flatness and thickness variation information concerning transmissive plane-parallel test plates is obtained from a grazing incidence interferometer modified to distinguish between superimposed interference patterns containing both types of information. The grazing angle of the interferometer is varied, and unique modulation frequencies of local fringe intensities within the superimposed interference patterns are identified. The local fringe intensities attributable to the different interference patterns are distinguished by their respective modulation frequencies.

Abstract: An interference filter (10, 30, 50, 70, 90, 110, 130, 150, or 190) filters selected wavelengths by dividing an input beam into two or more intermediate beams having different optical path lengths and by recombining the intermediate beams into an output beam that is modified by interference between the intermediate beams. An optical path length difference generator (20, 40, 60, 80, 100, 120, 140, 160, or 200) varies the optical path lengths of the intermediate beams by changing the physical lengths of their paths or the refractive indices of the mediums in which they are conveyed. The optical path length generator (20) of one exemplary embodiment (10) includes a spacer plate (20) that is divided into elements (22 and 24) having different refractive indices for varying the optical path lengths of the intermediate beams.

Abstract: Optical interference filters are designed with harmonic elements that can be related to Fourier series approximations of desired filter responses. The harmonic elements can be fashioned as individual waveguides of an array arranged in various formats including planar or concentric geometries. The expansion coefficients of the Fourier series correspond to normalized power distributions among the waveguides, and the harmonic components of the series correspond to incremental optical path length differences between the waveguides.

Abstract: A coupling for an optical device that disperses wavelengths along a focal line includes reflective surfaces that fold light out of a plane propagation and into alignment with an array of inputs or outputs. Some of the reflective surfaces are offset from the focal line so that the inputs or outputs can be spaced closer together in a dimension along the focal line.