Pattern generators, calibration systems and methods for patterning workpieces

A pattern generator comprising:

• a writing tool configured to generate a pattern on a workpiece arranged on a stage;
• and
• a calibration system configured to determine a correlation between a coordinate system of the writing tool and a coordinate system of a calibration plate on one of the stage and the workpiece;
• wherein the calibration system is further configured to determine the correlation at least partly based on an optical correlation signal, or pattern, in a form of at least one optical beam reflected from at least one reflective pattern on a surface of the calibration plate;
• wherein the at least one reflective pattern has areas of differing reflectance, and the calibration plate is configured to reflect an optical beam for calibrating the spatial position, focus and dose of the optical beam.