3. Application to angle and straightness measurement

3.1 Application to angle measurement

Interferometry can also be used to measure angular displacements. To do this, simply replace the optics (splitter plate, moving and fixed mirrors) with two optical systems (figure 14 ):

• the first module, commonly known as the "angular interferometer", comprises a beam splitter and a mirror; the incident beam is split into two parallel beams of equal intensity, separated by a few centimetres;

• the second, commonly referred to as the "angular reflector", comprises two reflectors to reflect the two beams.

When the optics are strictly parallel,...