Method and apparatus for adjusting an optical element to achieve a precise length

摘要

In a device and method, the optical path length through an optical element is adjustable with high precision. The optical element has a first segment formed from a first optical material, the first segment having a first face at a first end and a second face at a second end opposing the first face, the second face being non-parallel with the first. The first and second faces are disposed on a beam path. The element also includes a second segment formed from a second optical material, having a third face at a third end and a fourth face at a fourth end opposing the third face, the third face being non-parallel with the fourth face. At least one of the first and second segments is translatable across the beam path so as to change an optical path length through the optical element.