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A variable lateral shear heterodyne interferometer has been developed that is capable, for example, of measuring the high-bandwidth wave fronts in adaptive optical systems. The interferometer is used with a radial Ronchi grating and operates with a variety of spatially and temporally coherent light sources such as whitelight extended sources. The interferometer has been operated successfully in a real-time atmospheric compensation adaptive optical system.

A subaperture configuration to test aspheric optical components or systems has been developed. The aperture is divided into annular subaperture regions, and an interferometer is refocused for each region to reduce the fringe density. The method is suited to phase-measuring interferometry and may be used with standard interferogram reduction software. The theoretical basis for the method, requirements for the number of annular zones, sensitivity to the selection of the number of polynomials, and tolerances for centration and radius are described. Numerical and experimental validations of the algorithm are described. The method may eliminate the need to use null lenses for measuring some aspheres at the center of curvature.

Projection-type moiré contouring can be done without a reference grid by undersampling projected cosine fringes with a charged-coupled-device detector array to eliminate entirely the unwanted sum, shadow, and grid terms of classical moiré methods as well as the spurious moiré fringes that are due to higher harmonics. The technique produces a high-visibility sampled version of the moiré difference contour fringes. Higher-order aliasing can provide increased sensitivity when the same detector array is used. The sampling conditions are formulated as a moiré extension to the Whittaker-Shannon sampling theorem.

We describe a simple common-path self-referencing interferometric method requiring no auxiliary optical elements which accurately and directly measures the thermal diffusivity of anisotropic crystals in nonsteadystate conditions. We determine the thermal diffusivity of a lithium niobate crystal as a function of temperature ranging from room temperature up to 500 degrees C.

Infrared interferometry is used for testing both infrared materials that are opaque in the visible and optical surfaces still in the ground-glass condition. A pyroelectric vidicon is used to detect infrared interference fringes, which can be phase shifted, allowing precise measurements of the infrared wavefront. This paper discusses the pyroelectric vidicon as a detector of infrared interference fringes and the limitations it presents when used to obtain accurate phase-shifted measurements of an infrared optical wavefront.

This paper describes an acoustooptic technique for achieving signal correlation with a time-bandwidth product of 10(6)-10(8), using existing devices. One signal is used to intensity modulate a light beam that illuminates an acoustic cell. The other signal appears in the cell as a traveling wave and is Schlieren imaged onto a detector array. The detected image intensity is integrated in time, achieving the desired correlation function. Since the correlation integration is performed in time rather than space, the time-bandwidth limitations of earlier acoustooptic correlators are greatly reduced. Experimental procedures for implementation of this technique are discussed and results shown.