Two-flat absolute test solutions based on pixel rotation averaging

Absolute testing is an important means of measuring the surface deviation with high precision. A novel method is proposed to approach solutions of the absolute surface 3-D distributions that based on the two-flat method. Measurement data are separated into even and odd part and the rotation averaging method is used to calculate the rotation variant part. The performance of this new method is evaluated by compared with the method in the literature. The maximum difference of peak to valley (PV) and root mean square (RMS) between the two methods are 2.3nm and 0.4nm, respectively. The advantage of this method is that it can obtain the surface information of the low and mid-spatial frequency. The repeatability error propagation of the proposed method is discussed.