Patent ID: 8614798

Claim:
A pattern generator comprising: a stage; a workpiece arranged on the stage; a calibration plate on one of the stage and the workpiece; a writing tool configured to provide a writing optical beam for generating a pattern on the workpiece arranged on the stage; and an alignment system configured to determine a correlation between the position of the writing optical beam of the writing tool and the coordinate system of the calibration plate; wherein the calibration plate includes, a plurality of horizontal reflective patterns arranged to match a one-dimensional line image pattern of an optical beam impinging on the calibration plate, the plurality of horizontal reflective patterns being configured to match the pattern of the impinging optical beam to produce an optical correlation signal for measuring y-scale and y-offset of the writing optical beam, and a plurality of sets of vertical reflective bars having a set of slanted reflective bars interlaced between the vertical reflective bars, the plurality of sets of vertical reflective bars being configured to match the one-dimensional line image pattern of the impinging optical beam to produce an optical correlation signal for measuring x-scale and x-offset of the writing optical beam, and the at least one set of slanted reflective bars being arranged to match the one-dimensional line image pattern of the optical beam impinging in a single sweep over the calibration plate to produce an optical correlation signal for measuring x- and y-positions of the writing optical beam.