Abstract: A prealigner (10) employs an X-Y stage (20) and a rotary stage (26) to position and orient a specimen (12) without centering it on the prealigner. In a preferred embodiment, the rotary stage is mounted on the X-Y stage and receives a semiconductor (12) in a substantially arbitrary position and orientation. The prealigner employs the rotary stage and translation in only an X-axis direction to scan the peripheral edge (76) of the wafer across an optical scanning assembly (36) to form a polar coordinate map of the wafer. A microprocessor (162) determines the location and orientation of the wafer from the map and cooperates with a motor drive controller (122) to generate control signals for positioning and orienting the wafer in the preselected alignment without changing the location at which the wafer is held.

Abstract: A high precision linear actuator includes high fidelity mechanical linkages between the motor drive and the linear displacement output shaft. Rotational motor drive output is conveyed to a rotatable spindle (20) and lead nut assembly by means of belt driven sprockets. Rotation of the lead nut assembly is converted to linear displacement of a non-rotating lead screw and output shaft. Linear actuators of the present invention also incorporate a feedback control feature employing Moire fringe pattern techniques to continuously monitor the position of the output shaft.

Abstract: A method and an apparatus scan a light beam (62) along an arcuate scan path (148 and 150) across a bar code symbol (48) to decode it. In a preferred embodiment, a robotic semiconductor wafer handler (10) rotates a fixed-beam optical scanning assembly (44) beneath the bar code symbol inscribed in and near the periphery of the bottom surface (50) of a stationary semiconductor wafer (12). The rotation of the optical scanning assembly is characterized as a series of angular positions. The bar code symbol is decoded by determining the angular position of each of the bars of the bar code symbol during the rotation of the optical scanning assembly. A microprocessor-based scan data processing system (60) included within the wafer handler carries out a decoding algorithm to determine the distances between adjacent bars, thereby to decode the bar code symbol.