Single-Exposure Long-Equivalent-Wavelength Interferometry

Proposed single-exposure technique for producing long-equivalent-wavelength interferograms (LEWI's) involves use of photographic film to record two-wavelength interferogram nonlinearly in single exposure. Nonlinearity required to produce difference-spatial-frequency Fourier component containing LEWI information obtained by adjusting exposure so it falls on nonlinear portion of sensitivity curve of film. After two-wavelength interferogram recorded, film developed in conventional manner. Possible to use LEWI's to measure surface contours of such objects as human corneas, not expected to remain stationary for two exposures. Commercial interferogram-processing computer programs used to convert LEWI's into topographical representations of surfaces.