Research On Saturation And Crosstalk Of Infrared Imaging System

With the development of laser interference,the mechanism of saturation crosstalk effect of sensors and its enhancement methods have been paid more and more attention by researchers.In this paper,the imaging link model is established from three parts:laser,optical machine system and detector response,and the optical saturation crosstalk effect is studied.The main points are:Firstly,the mechanism of optical crosstalk and electrical crosstalk is analyzed.The optical crosstalk coming from optical system,diffraction effect,detector structure and so on is much larger than electrical crosstalk.According to the actual needs,the optical system parameters were set and the optical system design was completed.The optical system was evaluated for image quality and tolerance,and the tolerance range of the machining was given.The mechanical structure was designed on basis of the optical system structure and an optical machine model was established to analyze stray-light with software of Tracepro.The stray-light analysis is carried out,and the stray light coefficient of the optomechanical system is 0.01,PST is 10^-5 in the 10°field of view.The level of internal radiation is 0.004%,which meets the requirements of stray radiation.Secondly,the structure and the mechanism of the detector are determined according to the literature research.The response of the detector,including the photogenerated and thermoelectric emf,is related to the carrier diffusion,carrier drift and carrier compound by using the PN junction principle.The key parameters affecting the detector response are analyzed and determined.According to the classical photogenerated electromotive force model,the response curve of the detector is obtained with Matlab.The result is that the voltage is linear first with the increase of the incident light power density.Increase and then stabilize.Based on the analysis of the detector response curve,it is determined that the detector's saturation power density threshold is 2W/cm².Finally,the saturated crosstalk analysis is performed according to the optical system diffraction theory and the scattering theory.Using Matlab simulation method,when the incident laser energy density is 1.17417×10⁵W/cm²,the number of saturated pixels of the spot at different positions is 540,the saturated pixel number is 346 when the duty ratio of the detector pixel is considered by discrete method.By extracting the energy of the saturated region,the crosstalk amount of the non-image area is calculated to be 11.85%.Based on the saturation of the detector,the model of the entire imaging link is established by Tracepro,and the image illuminance map and ray path data are obtained.The image plane dispersion and the saturation of the 2°field of view are calculated by the image plane discrete method.The number of pixels is 0,and the laser emission power is amplified by 125 times according to the same method,the number of saturated pixels is calculated to be 22 and 18.The detector structure model is established.The crosstalk of the single layer structure is 0.0436 when the fill factor is 64%,the crosstalk of the double layer structure is 0.00036,and the crosstalk of the single layer structure when the fill factor is decreased is 0.06284.A method for suppressing crosstalk by improving the detector filter layer structure and increasing the fill factor is given.