Metrology is the science of measuring distances. There are different approaches for optical measuring:

• Time of Flight
• Triangulation
• Interferometry

Interferometry is the most accurate way of measuring distances. It makes use of the wave properties of light. There are different interferometric measuring apploaches like Absolute Distance Interferometry (ADI), Speckle Interferometry (SI), or Mode Locking External Cavity Sensor (MolECL). The accurancy of all interferometric measuring methods is in the sub-micron range.