Research On Stray Radiation Transmission For Infrared Detecting System With A Window Coated By Thin Film

Infrared detection is an important part of optical detection.With the further development of detection technology,improving the detection accuracy and expanding the detection distance have become the inevitable requirement of infrared detecting development.For infrared detection,the infrared radiation of internal infrared components and infrared window themself will evolve into stray radiation,which will seriously affect the image quality and reduce the image resolution.Therefore,establishing window infrared radiation model and carrying out the analysis of stray radiation transmission in the multi-source detection system as well as targeted to take suppressing measures are of great importance to improving detecting quality.In this thesis,the infrared detection system with a coated window is used as the object of study.The model of researching window infrared radiation is established and the stray radiation transmission characteristics in the system is analyzed by Monte Carlo method.The effect of the antireflection film on the stray radiation and the detection accuracy in the system were further studied.This thesis is written from the following aspects.1.Two models for apparent radiation of window and the optical property of antireflection film are established.The apparent emission model can characterize the ability of the window to radiate energy to the outside space of the medium and the directional characteristics of the radiant energy.When calculating the stray transmission of the light machine system,using this model can make the window media be equivalent to a single interface,thus simplifying the calculation and improving the computational efficiency.The model of the optical property of the antireflective film is deduced based on the theory of thin-film optics and the reflectivity of the direction band at the interface of the coating can be obtained.2.For infrared detection system,infrared stray radiation transmission characteristics in the system is analyzed utilizing the self-programming code based on the Monte Carlo method.The distribution of the main stray sources in the system,the dangerous path of the stray radiation transmission,the distribution of the stray radiation on the entrance pupil surface and the incident direction are obtained,which provide the basis for the subsequent stray suppression.3.The synergistic properties of the antireflective film are obtained by coupling the model of antireflective film optical properties to the stray radiation solver code.The influence of the antireflection coating on the internal radiation transmission is described from three aspects: the apparent emission characteristics of the medium,the transmission of stray radiation and the detection accuracy in the system.