Spatially selective laser irradiation method controlled by real-time image analysis: optical aspects.

We present a spatially selective irradiation method for laser treatment of biological surfaces. The purpose is to irradiate only the pathological targets and to preserve the healthy surrounding parts. We are interested here in the optical arrangement of the device and in the evaluation of its physical limitations before it is used for medical purposes. The method uses real-time image analysis applied to the video imagery of the surface to be treated. The result of the image analysis generates the control signal to a spatial light modulator, allowing us to project an adequate repartition of laser irradiance on the surface to be treated. Experimental results demonstrate a spatial selectivity of similar to10 mum for a 6.7 mm X 5 mm field. The optical system has no moving parts (unlike galvanometric scanners) and is able to irradiate multiple targets simultaneously with different doses. (C) 2005 Optical Society of America.