Image information by means of speckle pattern processing

When a laser beam is reflected from a diffuse surface, a granular scattering distribution is commonly observed, called a speckle pattern. The author discusses some of its ramifications: (1) that this pattern is the time-dependent analogue of the signal used in the classic Hanbury Brown - Twiss stellar interferometer of the 1950's; (2) that this pattern can be processed by standard incoherent optical techniques to yield information pertaining to the object radiance distribution; (3) that this same signal, when processed by coherent-optical techniques, is equivalent to the Gabor on-axis hologram or the Fourier-transform hologram, depending on the specific source configuration; and (4) that signals processed by all of the above techniques are comparatively insensitive to atmospheric turbulence. An experiment is performed to illustrate the procedure of item (2) and then modified to show assertion (4).