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(Journal Article) |
Journal of biomedical optics 18 (6): 066018 (2013)
Laser speckle contrast imaging: theoretical and practical limitations.
David Briers
,
Donald D Duncan
,
Evan Hirst
,
Sean J Kirkpatrick
,
Marcus Larsson
,
Wiendelt Steenbergen
,
Tomas Stromberg
,
Oliver B Thompson
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.