The Coefficient of Finesse is from a Fabry-Pérot Interferometer, which is made of a transparent plate with two reflecting surfaces, or two parallel highly reflecting mirrors. The following formula is used: `F=(4R)/(1-R)^2`, where:
- `R` = Reflectance
- `F` = Coefficient of Finesse
References
The formula and definition are from Wikipedia (https://en.wikipedia.org/wiki/Fabry%E2%80%93P%C3%A9rot_interferometer#Theory).
