Patent ID: 8027042

Claim:
A multi-beam interferometer comprising a multiple beam source, the multiple beam source configured to provide a plurality of beams of light for use in the interferometer, the multiple beam source comprising: a light source configured to emit a beam of light; and a rattle plate comprising a first reflective surface and a second reflective surface facing one another, the second reflective surface being only partially reflective; in which the light source and the rattle plate are positioned relative to one another such that, in use, the beam of light is incident on the rattle plate such that the beam of light is repeatedly reflected along a beam path between the first and second reflective surfaces, each successive and spaced-apart reflection off the partially reflective second reflective surface causing a portion of the light beam to be transmitted through the second reflective surface to form one of the beams of the plurality of beams; and in which between at least one successive pair of beams of the plurality of beams there is a decrease along the beam path in a level of reflectance of the second reflective surface.