Abstract

This paper presents experimental work in which white-light illumination was used both for generating a speckle field in the recording process and for speckle noise suppression in the optical filtering process. In recording, a mechanically polished surface is clamped to a photoplate and is illuminated by an ordinary white-light source (such as a flashlight). The speckle field is generated by the interference of the partially coherent reflected wavelets. This speckle generation mechanism is different from the laser speckle method, in which highly coherent light illumination is necessary for speckle generation, and from the conventional white-light speckle method, in which a speckle pattern is either artificially created or naturally present. This speckle field is directly recorded on the photoplate without using any lens, resulting in sensitivity improvement. A double-exposure specklegram produced with this arrangement is then placed in an optical filtering processor with white-light illumination to yield information-carrying fringes. Speckle noise, which would appear strongly in the coherent optical filtering process, is effectively suppressed by this approach. This objective coherent white-light speckle method has many advantages. For example, there is no need for either a recording lens or a coherent light source. The specimen surface needs no special treatment, and it is capable of generating fringes with high sensitivity and low noise. Both theoretical analysis and applications of this method to practical problems are presented.

© 1985 Optical Society of America