Abstract: The present invention relates to a non-contact holder for substantially planar workpieces, particularly suited for holding thin workpieces without substantial distortion. The present invention includes a cylindrical chuck having a gas inlet orifice positioned at an oblique. The introduction of pressurized gas creates a vortex and vacuum attraction holding a wafer in close proximity to the chuck while the gas exiting from the chuck prevents contact between wafer and chuck. Small diameter chucks located in close proximity help the present invention avoid distortion when processing very thin workpieces. The gas exiting from the chuck of the present invention exits preferentially in a certain angular direction. Chucks are arranged on the wafer holder such that exiting gas is preferentially directed radially towards the periphery of the holder and that exiting gas is directed between adjacent chucks, not directly at another nearby chuck.

Abstract: The present invention discloses an apparatus in which two laser beams are concurrently scanned across a region of tissue to be treated by laser therapy. A first "analysis" beam is used to excite characteristic light emission or reflection from the surface. This scattered light is detected and analyzed to determine the properties of the small portion of the surface under illumination and at that instant by the analysis beam. A second "treatment" beam is scanned concurrently with the analysis beam. The properties of the surface at each small region (as determined by the analysis beam) are used to adjust the power and other properties of the treatment beam such that each small region of the surface receives optimal exposure. Automatic controlled scanning of both beams allows very rapid treatment of large areas of tissue, while adjusting in real-time the power levels of the lasers to achieve optimal treatment at each point treated.