Three-dimensional acousto-optic imaging in biological tissues with parallel signal processing.

An original acousto-optic method is described that allows one to reveal optical contrasts through biological tissues that are several centimeters thick with a millimeter-sized resolution. This technique is based on the interaction of scattered laser light with a focused ultrasonic field. The modulation depth of the optical speckle is related to local optical properties of the sample. Our parallel-processing approach to the demodulation of the speckle improves the observed degree of modulation by 2 orders of magnitude and quickly yields a good statistical value. Optically absorbing objects were imaged inside 35-mm-thick biological tissues.