With multiple beam interferometers it is possible to measure several lengths and angles with high precision. The angle is calculated from the length difference and the beam distance.
One HeNe laser shares the light between all the beams. Therefore the measurements can be traced back to the same laser wave length. The laser light is guided to the sensor head by an optical fiber.
The drawing shows a measurement made by a triple beam interferometer. Three lengths, the pitch and the yaw angle are all measured simultaneously.
Application areas for such measurements are linear guide characterization, calibration of measurement machines, high resolution angle measurements, multi coordinate measurements and differential measurements.