Abstract

It is well known that when a diffusing surface is illuminated by a coherent or quasi-monochromatic light source, a volume of random speckle is created. We examine a new phenomenon: when a diffusing surface is illuminated by a broad bandlimited or even white-light source (e.g., incandescent lamp, arc lamp, or sunlight) a field of colored speckles exists in the region near the rough surface. We refer to them as chromatic speckles. In this article we explore the statistical properties of the chromatic speckle, its 3-D size and its relationship to the roughness of the generating surface. We also explore the use of chromatic speckle to metrology. Compared with laser speckle and random pattern photography, the chromatic speckle method has many advantages. For example, it requires only a simple white-light source for recording. The chromatic specklegram can also be processed by white light resulting in low noise fringes. In addition, because of the longer axial length of the chromatic speckle the method can be applied to measuring out-of-plane as well as inplane deformations. Experimental results are presented.

© 1985 Optical Society of America