Abstract

Subfringe displacement information is recorded and may be extracted using heterodyne interferometric techniques to read out a holographic record. Heterodyne techniques employ any of several methods to ensure that light arriving at the output plane from one virtual object is at a slightly different frequency from light arriving from the other virtual object reconstructed from the hologram. The effect of frequency shifting one of the light beams is to cause the intensity of the image in the output plane to vary periodically at the difference frequency of the two beams. While the frequency of the intensity variation is the same at every point on the object surface, different points in the image plane may not fluctuate precisely in phase with each other. The degree of phase difference in intensity fluctuation between two points in the observation plane is directly related to the difference in surface displacement between the two points.

© 1985 Optical Society of America