Patent ID: 9587933
Date: 2017-03-07
CPC Classifications: G01B,G01N

Claim:
1. A method for inspecting one or more subject gratings on at least a portion of a test object, the method comprising: receiving a test image of at least the portion of the test object, wherein the test image comprises a test moiré pattern generated by superposing one or more reference gratings on the one or more subject gratings; analyzing one or more test beat lines in the test moiré pattern; calculating one or more test values based on the analysis of the one or more test beat lines, wherein the one or more test values are a function of one or more rotational angles corresponding to the one or more subject gratings and a shape of at least the portion of the test object; calculating one or more angular errors of the one or more subject gratings based on the one or more test values and one or more template values; and sending a notification to a user based on the one or more angular errors.