Method and apparatus for tilt corrected lateral shear in a lateral shear plus rotational shear absolute flat test

摘要

A Fizeau or other interferometer is used to provide high resolution, in-situ calibration of an external angle measurement system such as widely spaced high stability plane mirror interferometers (HSPMIs)). The calibrated measurement system then measures mechanical tilt during shearing. The tilt data is used to correct the sheared data, preferably before computation of the rotationally invariant (RI) terms. Altematively, the data may be used to compute the spurious quadratic term and correct after integration.