Modeled and Measured Image-plane Polychromatic Speckle Contrast

Document Type


Publication Date



The statistical properties of speckle relevant to short- to medium-range (tactical) active tracking involving polychromatic illumination are investigated. A numerical model is developed to allow rapid simulation of speckled images including the speckle contrast reduction effects of illuminator bandwidth, surface slope, and roughness, and the polarization properties of both the source and the reflection. Regarding surface slope (relative orientation of the surface normal and illumination/observation directions), Huntley’s theory for speckle contrast, which employs geometrical approximations to decrease computation time, is modified to increase accuracy by incorporation of a geometrical correction factor and better treatment of roughness and polarization. The resulting model shows excellent agreement with more exact theory over a wide range. An experiment is conducted to validate both the numerical model developed here and existing theory. A diode laser source with coherence length of 259±7  μm is reflected off of a silver-coated diffuse surface. Speckle data are gathered for 16 surface slope angles corresponding to speckle contrast between about 0.55 and 1. Taking the measured data as truth, both equations show error mean and standard deviation of less than 3%. Thus, the theory is validated over the range of this experiment.


© The Authors. This is an open access article published by SPIE under a Creative Commons Attribution 4.0 Unported License (CC BY 4.0). Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

The "Link to Full Text" opens the full text of the article (HTML) at the publisher website. A PDF of the article is also available at that page.



Source Publication

Optical Engineering