Laser speckle contrast imaging: theoretical and practical limitations

Briers, David, Duncan, Donald D, Hirst, Evan, Kirkpatrick, Sean J, Larsson, Marcus, Steenbergen, Wiendelt, Stromberg, Tomas and Thompson, Oliver B (2013) Laser speckle contrast imaging: theoretical and practical limitations. Journal of Biomedical Optics (JBO), 18(6), p. 66018. ISSN (print) 1083-3668

Abstract

ABSTRACT. When laser light illuminates a diffuse object, it produces a random interference effect known as a speckle pattern. If there is movement in the object, the speckles fluctuate in intensity. These fluctuations can provide information about the movement. A simple way of accessing this information is to image the speckle pattern with an exposure time longer than the shortest speckle fluctuation time scale-the fluctuations cause a blurring of the speckle, leading to a reduction in the local speckle contrast. Thus, velocity distributions are coded as speckle contrast variations. The same information can be obtained by using the Doppler effect, but producing a two-dimensional Doppler map requires either scanning of the laser beam or imaging with a high-speed camera: laser speckle contrast imaging (LSCI) avoids the need to scan and can be performed with a normal CCD- or CMOS-camera. LSCI is used primarily to map flow systems, especially blood flow. The development of LSCI is reviewed and its limitations and problems are investigated.

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