Pointwise deviation is a direct method used to represent the differences between the measurement results obtained from different instruments. Based on this result, the RMS values of the pointwise deviation were insufficient for evaluating consistency, although the two error maps were consistent in some characteristic areas.

The “CGH” and “LPS” error maps demonstrate favorable consistency over the entire frequency band, particularly for the low- to mid-frequency bands below 0.16 mm-1, with an average value of 4 nm. According to the “Delta” curve, a relatively significant deviation only occurred in the high-frequency band ranging from 0.16 to 0.36 mm−1, with a maximum deviation of 6.8 nm.