Lasers are suitable for high-precision measurements due to their long coherence length. The principle of interferometry is used here. The best-known arrangement is the Michelson interferometer.
The general function of a Michelson interferometer is that a beam from the same light source is split into two identical light beams. Each of these beams travels a different path and is then recombined with the other beam before hitting a detector. Due to the different path lengths that each beam travels, there is a phase difference between these two beams. This phase difference creates what is known as an interference pattern, consisting of light and dark zones. The evaluation of this interference pattern allows conclusions to be drawn about the phase difference between the two partial beams. In this way, the smallest path differences between the partial beams can be measured with high precision. This allows not only distances to be determined, but also the smallest deviations in linearity, angle or flatness. One of the main applications is therefore the in-situ measurement of workpieces in CNC machines. Formula 1 car bodies are also measured with LASOS lasers because even the smallest deviations can make all the difference.
The main products for precision measurement technology are LASOS He-Ne lasers. Their inherently high coherence can be increased even further by simple means. One frequently used method is to heat the He-Ne tube in order to stabilize the resonator length using a special control system.