Study On Suppression And Analysis Of Stray Light In Infrared Detector Assembly

Stray light first easily affects the performance of IR detector module, then influences the image quality of IR detection system, thus suppression of stray light of IR detector module as the core device of target detection and imaging is important. In order to study optical crosstalk of multi-band detector and suppression of stray of Focal Place Array(FPA) detector, a set of micro-spot measuring system is improved, while a Point Source Transmittance(PST) test set-up is developed. Two sets of test device are employed to evaluate stray light of detector module, some measures of restraining stray light is proposed in paper, which is useful for engineering application of detector module.Firstly, the propagation theory and research trends at home and abroad of stray light are briefly introduced in paper. The propagation of stray light depends on three factors: Bidirectional Reflectance Distraction Function(BRDF), Geometry Composing Function(GCF), and incident radiation flux, thus suppression of stray light is from three aspects of background suppression, structure design and surface treatment technology. Optical software simulation and parameter measurement are currently employed to evaluate stray light of IR detector module. Stray light test system is developed to acquire the value of optical crosstalk and PST, and validate the capability of restraining stray light of IR detector module in paper.Secondly,the optical crosstalk of different structure of IR detector module is measured and discussed, then the source of stray light is analyzed and some method of restraining stray light is suggested. Fourier response spectrum is good at analysing the out-of-band stray light of IR detector module, but that’s all. In order to study the spatial distribution of stray light of IR detector module, We improve the IR micro-spot test system, meanwhile, three key problems consist of acquisition of weak signal, high precision alignment of 30μm fine bright strip and automatic data acquisition is solved. The experiments verify that reproducibility of IR micro-spot system is better than 96% and focus size of slit is about 30μm, then the Line Spread Function(LSF) of three bands of IR detector module consist of medium and short band, water band, long band is tested by the test system and the optical crosstalk of detector module is analyzed. The optical crosstalk of detector module with different structure is used to confirm that the profile of overlap electric region is photosensitive, which is the main factor to cause the deterioration of modulation transfer function(MTF) of detector module. The results also demonstrate that shorter distance between filter and chip would be the more beneficial to control of stray light in IR detector module.Finally,The test and evaluation methods to control stray light of FPA detector dewar module is studied. The method of retrace rays is used to calculate the efficiency of cold shield instead of complex formula calculation, and the influence of cold shield to response uniformity of FPA detector is known. In order to test and evaluate the effect of cold shield to control of stray light, we design and set up a test system to test PST of cold shield, meanwhile, problem of uniformity of image plane intensity of light from system’s light source is solved. The relation curves between PST with angle for cold shield with different structure are measured and consistent with numerical simulation. Some constructive measures for optimizing design of infrared detector modules for control of stray light are proposed.