Patent ID: 6943885

Claim:
A gas cell comprising a body having a cavity therein adapted for a chosen gas volume, a partially elliptical surface forming a reflector for a light source, the partially elliptical surface being comprised of two partially elliptical mirror surfaces, each partially elliptical mirror surface having an end part away from the other of the partially elliptical mirror surfaces, and the partially elliptical surface having a first focal point and a second focal point spaced from the first focal point; a light source at the first focal point; the light source including an incandescent filament with a length; two other cavity-defining and gas-conducting surfaces each extending respectively from one of the end-parts of the mirror surfaces; a light-bundle receiving unit at the second focal point of the partially elliptical surface; the cavity is delimited spaced apart parallel surfaces defining the cavity and meeting the partially elliptical mirror surfaces and the other cavity defining surfaces, wherein the distance between the spaced apart parallel surfaces corresponds essentially to the length of the incandescent filament in the light source.