A chuck adapted to support a substrate includes an array of glass bars spaced apart and each having a number of holes in its supporting surface. The holes in the supporting surfaces are connected to a common conduit that is supplied with air to provide an air cushion to support the substrate during loading and positioning operations. Scrubbers in contact with one or more edges of the substrate are used to locate the substrate precisely relative to a mechanical reference. After the substrate is positioned at the desired location, the common conduit is separately supplied with vacuum to provide a suction force to hold the substrate to the chuck. The array of glass bars are designed to operate in conjunction with a multi-light backlight system that provides uniform illumination for areas of the substrate that are supported above a glass bar as well as for areas of the substrate that are positioned between the glass bars.
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