INTERFEROMETER HEAD WITH DIRECTIONAL SENSITIVITY

摘要

An interferometer head is disclosed. A first portion of an input radiation beam is incident on a first partially-reflective surfaee and reflected from a first reference surface towards a first output terminal. A second portion of the input radiation beam is incident on a second partially-refleetive surface and reflected from a second reference surface towards a second output terminal. A third portion of the input radiation beam is transmitted towards a measurement surface. A first portion of a reflected beam from the measurement surface is reflected from the second partially-reflective surface towards the second output terminal. A second portion of the reflected beam from the measurement surface is reflected from the first partially-reflective surface towards the first output terminal. An offset angle is implemented between a first output radiation beam from the first output terminal and a second output radiation beam from the second output terminal.