Linear-and-angular measuring plane mirror interferometer

An interferometer for measuring the linear motion of an object along a first axis and the angular motion of the object around a second axis orthogonal to the first axis, using a single integral optical assembly, comprising:

• light source means for producing a coherent light beam;
• reflecting means mounted on a movable measurement plane located on the object, for reflecting the beam;
• integral optical assembly means for directing the beam along a first path between the optical means and the reflecting means, and along a second path between the optical means and the reflecting means, the first path incident on the reflecting means at only two points around a first location and the second path incident on the reflecting means at only two points around a location, the first and second locations separated by a distance d;
• means for determining the change in the length of the first path;
• means for determining the difference between the change in the length of the first path and the change in the length of the second path, and for calculating the angular motion of the object based on the result.