Absolute Testing for a EURAMET Comparison on a PTB Optical Flat at an Aperture of 300 mm

The measurement and calibration of high-quality flats have been playing an important role for optical systems in optics and precision engineering. Hence, many National Metrology Institutes offer corresponding calibrations services. It is well known, laser interferometry technique is a very effective method to evaluate high-quality surfaces. Typically, transmission flat has PV lamda/20. However, when a flat surface under test is better or much better than the transmission flat, we do need the absolute calibration technique. In this talk, we will talk about absolute testing for a EURAMET comparison on a PTB optical flat at an aperture of 300 mm, and dedicate theoretical analysis, computer simulations, and experimental validation.