Patent ID: 8653461

Claim:
An infrared camera system, comprising: a lens adapted to receive infrared radiation from a survey scene comprising one or more gasses; a focal plane array comprising a plurality of quantum well infrared photo detectors (QWIPs) comprising: a plurality of quantum well layers comprising gallium arsenide (GaAs) doped with silicon to generate a desired flow of free electrons in response to the radiation, a plurality of barrier layers alternating with the quantum well layers and comprising aluminum gallium arsenide (AlGaAs), wherein: the quantum well layers and the barrier layers have associated thicknesses, an amount of silicon doping, a spacing of quantum wells in the quantum well layers, and the thicknesses of the quantum well layers and the barrier layers are selected for the QWIPs to tune the QWIPs to have a limited spectral bandwidth with a peak response within a wavelength range of 10.4 μm to 10.8 μm corresponding to at least a portion of an infrared absorption band of the one or more gasses and to have a full width half maximum spectral bandwidth of less than 0.7 μm in response to the radiation; and an optical band pass filter positioned substantially between the lens and the focal plane array and adapted to filter the infrared radiation to a wavelength range substantially corresponding to the limited spectral bandwidth of the QWIPs before the infrared radiation is received by the focal plane array, wherein the less than 0.7 μm spectral bandwidth of the focal plane array is selected to reduce signal noise substantially outside the wavelength range of 10.4 μm to 10.8 μm associated with the optical band pass filter and/or the focal plane array.