IR FPA performance modeling and testing
Infrared Focal Plane Array (IR FPA) performance modeling allows to predict signals, noise and photoelectric characteristics of any Photo Detecting Assembly (PDA), to analyze a dependence of these characteristics from design and operating parameters and to carry out their optimization. Advantage of this model is the accurate calculation of characteristics for the IR FPA with an arbitrary aperture of the cold shield. This capability is based on a new concept of the FPA irradiation. It is proved that a background irradiation at array arbitrary point of IR FPA is product of an aperture transmittance and array irradiance of the extended source located outside of the aperture in a hemisphere. The cold shield aperture transmittance is a new parameter. It is determined by integral of aperture area. The integral includes coordinates of an array arbitrary point, cold shield aperture shape, distance between the array plane and the cold shield aperture plane. An outside array irradiance in hemisphere is defined by Planks’ formula. In other words, the FPA irradiation is the irradiation from a source which is filling the cold shield aperture. A source temperature distribution over the aperture is defined by projection of outside source temperature points to preset array point through aperture. Experimental testing of model correctness was made by comparing the signal and noise characteristics of different IR FPA with known structural and operational parameters. They were sensitive in the spectral ranges of 0.9-1.7 mm, 3-5 mm and 8-11 mm. An adequate confirmation of the model correctness was received.