Calibration method of prealignment machine

CALIBRATION METHOD prealignment machine, a robot to a wafer placed on a pre-alignment unit; determining said mechanical hand coordinate system and the pre-aligner opposite directions, comprising the steps of: placing the wafer on the robot to the pre- the quasi machine, the wafer center point position in a first coordinate system a first pre-alignment unit is located in; pre-alignment unit recognizes the coordinate position of a first point in the first coordinate system; manipulator driven along the wafer a second horizontal axis of the robot coordinate system where a moving distance of the wafer center point reaches a second position; pre-alignment unit recognizes the coordinate position of the second point in the first coordinate system; calculating a first position the angle between the horizontal axis and the point position of the second connecting point of the first coordinate system, is the opposite direction of the first coordinate system and the second coordinate system; wafer position adjustment of the robot, the wafer is pre-alignment.