A method detects a center of a wafer having a notch when aligning the wafer mounted on a movable mounting table. Mounted in a cam chamber is a control cam that is driven by the crankshaft of the engine and on the cam path of which rests a drag lever that transfers the cam lift to the rocker arm. The apparatus also includes a memory for storing correlation values successively output from the correlation detection circuit, wherein the pointer is detected based on the correlation values. Electron tunneling current across the gap is measured during the process environment exposure and the process environment is controlled during process environment exposure based on tunneling current measurement. In order to counter errors, patterns similar to the first data pattern are also substituted with new patterns.