The wafer orienter uses infrared light to determine the position of the wafer flat or notch .Infrared light is also used to determine the wafer center relative to the center of the chuck. The light is emitted by an infrared photo diode and is cillimated as it passes through a series of lenses. The Light is received by a charged coupling device(CCD) array. A filter assembly eliminates ambient light. All of the optical components except for the filter assembly are located outside the chamber.

Pixels within the CCD array collect the light from the infrared photo diode. The CCD PCB reads the charges produced by the pixels and determines the transition between light and darkness (the edge of the wafer).When the wafer is rotated, the variation of this transition signal determines the location of the wafer notch or flat.

After the wafer center is determined, an orienter software algorithm programs the robot to pick up the wafer at its center.