A summary of various commercially available lasers is given in Table 3.1. A helium-neon laser is most popular in measurements. For measurements in liquids and when multiple lines (wavelengths) are required, the Argon-Ion laser is preferred. This is because of its superior coherence at higher power outputs. A laser is unsuitable in the measurement context but is preferred in the manufacturing industry where operations such as drilling and cutting are common.

A summary of optical measurement techniques employed in various aplications is provided in Table 3.2. Examples where white light is used are included for completeness.

Table 3.1: Various types of lasers and their overall specification. An etalon is an optical interferometer contained within the laser that helps improve coherence of the light output.