Patent ID: 8269972

Claim:
A gas sensor comprising: an electromagnetic radiation source configured to emit an input beam of light; an optical cavity for receiving a gas to be detected, the optical cavity defined by one or more optical segments separating at least two mirrors, wherein the at least two mirrors are configured to reflect an internal beam of light through the one or more optical segments; an optical element disposed in at least one of the one or more optical segments, wherein the optical element is configured to reflect a portion of the internal beam of light when the input beam of light emitted by the electromagnetic radiation source is selectively allowed to enter the optical cavity; a first detector positioned to detect the portion of the internal beam of light reflected by the optical element, wherein the first detector is configured to produce a signal that is related to the intensity of the internal beam of light present in the optical cavity; and a controller coupled to the first detector, the controller is configured to receive the signal from the first detector and, when the controller determines that the intensity of the internal beam of light in the optical cavity has reached a threshold level, the controller is configured to cause the input beam of light emitted from the electromagnetic radiation source to be prevented from entering the optical cavity.