High-precision triangulation sensing of mirror surface

The analysis of measurement errors of distance up to a mirror surface by laser triangulation is given. We consider the two types of sensors: with output plane, orthogonal to the optical axis, and with tilted one (corresponding to the Scheimpflug principle). The conditions of Scheimpflug principle applicability for mirror surface testing are determined. We have shown, that at the certain ratio between parameters of optical system of the sensor and the probing light beam, the sensor with orthogonal plane of photoregistration can provide smaller level of measurement errors, than sensor with tilted plane, despite of the presence of defocusing.