Patent ID: 8289520

Claim:
A method, comprising: directing a light beam emitted by a narrowband light source through at least one etalon, the light beam being split into a first partial beam and a second partial beam, the first partial beam being directed n times through at least one etalon, the second partial beam being directed (n+k) times through the at least one etalon, n and k being integers â‰§1; directing the first partial beam that has passed through the at least one etalon n times and the second partial beam that has passed through the at least one etalon (n+k) times onto at least one light-sensitive detector; and evaluating the spectra recorded by the at least one detector of the first partial beam that has passed through the at least one etalon n times and of the second partial beam that has passed through the at least one etalon (n+k) times to determine a light spectrum corrected for an apparatus function of the at least one etalon, wherein the at least one etalon comprises a pair of opposing exterior surfaces, and wherein passing through the at least one etalon comprises entering the etalon through one of the exterior surfaces of the pair exterior surfaces and emerging from the etalon through the other exterior surface of the pair of exterior surfaces, and wherein a beam splitter is arranged downstream of the at least one etalon as viewed from the narrowband light source so that the light beam passes through the at least one etalon before being split by the beam splitter into the first partial beam and the second partial beam, and the second partial beam is directed back through the at least one etalon.