A semiconductor wafer transport apparatus having a transport arm and at least one end effector. An optical edge detection sensor is coupled to the transport arm and is configured so as to register and effect edge detection of a wafer supported by the end effector. An illumination source illuminates a surface of the wafer and is disposed with respect to the optical edge detection sensor so that the surface directs reflected surface illumination, from the illumination source, toward the optical edge detection sensor, and optically blanks, at the peripheral edge of the wafer, background reflection light of a background, viewed by the optical edge detection sensor coincident with linear traverse of the wafer supported by the at least one end effector. The peripheral edge of the wafer is defined in relief in image contrast to effect edge detection coincident with traverse of the wafer supported by the end effector.