Detection of inhomogeneities with ultrasound tagging of light

Ultrasound modulated light for optical tomography is very useful, since it can provide three-dimensional data with minimal mathematical processing. Al though several experimental studies have shown the potential of this method , the link between the ultrasound location and the modulated signal intensi ty at the detector is not yet fully understood. We derive an analytical for mula relating the position of the ultrasound transducer and the optical sig nal at the detector. We also derive an expression for the signal-to-shot-no ise ratio as a function of the transducer position. We show that in certain conditions this ratio is only slowly decreasing as a function of the light penetration depth, which makes this technique attractive for optical tomog raphy (C) 2001 Optical Society of America.