Development Of Large Angle Infrared Detection Filter For Optical Imaging System

Optical thin film has an important position in the field of imaging,while a single imaging method is difficult to detect and image all-weather targets,and is vulnerable to external interference in terms of information acquisition,leading to errors in judgement.Infra-red and micro-optical fusion imaging systems are mainly used for the identification of targets with low visibility in harsh environments,and accurate target detection can be achieved through dual-band imaging fusion technology.In the optical system for the fusion of Low light level night vision and infrared imaging,the light is divided into two beams by a beam splitter placed at 55°,where the reflected light is received by the LLL detector for LLL night vision imaging and the transmitted light is received by the infrared detector for infrared imaging,and the two imaging results are fused by image fusion to improve the imaging resolution.In combination with the imaging requirements of the imaging system,the performance of the optical components in the optical system is optimised and the spectral devices in the system are developed using physical vapour deposition methods.For the properties of the coated substrate and thin film materials,Zn S and Yb F₃were selected as the coating materials and multispectral Zn S as the substrate material.According to the thin film theory,the long wavelength pass interference cut-off filter film is selected as the base film system,and the problem of spectral curve error is solved by accurately calculating the optical constants of the coating materials;the problem of stress in the film layer of the spectroscopic device is solved by using the method of controlling stress with a specific single layer of film thickness,and the accuracy of the surface pattern of the film is improved.In the process of thin film preparation,for the problem that Zn S is easy to sputter during the deposition process,the method of increasing the deflector is proposed and its corresponding deposition process is improved,the deposition rate is more stable,which makes the defects on the surface of the film significantly reduced and improves the film quality on the surface of the film.Comparing the defects produced by different deposition methods of Yb F₃,it is found that the Yb F₃films deposited by electron beam heating are more dense,which can reduce the influence of water absorption and improve the denseness of the films;by studying the stress variation law of Zn S and Yb F₃monolayers by different processes,a structure with matching stress magnitude of high and low refractive index materials is selected,which makes the surface pattern of the film surface closer to the substrate surface,and in the subsequent inversion process This law can still be used to compensate for the stresses during the subsequent inversion.The final analysis of the film structure and the optimisation of the deposition process parameters have solved the problems of film layer solidity and surface shape accuracy,and achieved a spectral index of90.77%for visible/near-infrared reflectance and 91.15%for mid-infrared transmittance.Based on the principle of molecular motion,the annealing process was improved by analysing the causes of the formation of defects in the film ring test,improving the surface quality of the film layer,solving the problem of poor environmental resistance of the film,verifying the effect of annealing on the firmness of the film layer,improving the adhesion of the film layer,and preparing spectroscopic devices to meet the requirements of use.