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Wavefront investigation of a fourier transform lens with the fan trace interferometer.

The performance of a Fourier transform lens is analyzed with the help of a new interferometric device that records the aberration function along any selected section of the wavefront. These interferometric plots, which carry an automatic calibration, are analogous to the familiar geometric-optical fan ray traces and thus provide the means to compare the performance of completed lens systems with the design criteria. The interferometer is particularly well suited to test Fourier transform lenses; however, it is readily modified to investigate imaging systems as well. Therefore, photographic objectives or microscopes may also be analyzed with this interferometer, which also provides considerable freedom from alignment requirements.