摘要
在微光夜视与红外成像融合的光学系统中,光通过55°放置的分光镜分成两束光,其中反射光被微光探测器接收进行微光夜视成像,透射光被红外探测器接收进行红外成像,通过图像融合技术来提高系统的成像分辨率。针对分光镜的参数要求,笔者选用Ge、ZnS和YbF3作为沉积材料,采用离子源辅助沉积技术在多光谱ZnS基底上制备了0.6~0.9μm波段高反、3.7~4.8μm波段高透的分光膜。通过对膜系结构的优化以及沉积工艺参数的调整,解决了膜层牢固度和面形精度等问题,实现了0.6~0.9μm波段反射率为90.77%、3.7~4.8μm波段透射率为91.15%的分光指标。附着力测试、摩擦力测试、高低温测试、恒温恒湿测试结果显示所制备的双面膜可以满足使用要求,但该膜的短波反射率和长波透过率仍有一定的提升空间。
Objective There are significant differences in the actual optical characteristics of specific targets in different spectral bands.Thus,the two imaging systems shared an aperture for detection and identification.The internal light was separately imaged after passing through an optical device that separated the visible near-infrared and infrared light.In this way,the light from the two bands could be used to synchronously detect and image the target,allowing it to track the target more effectively.Thus,it could meet the all-day,wide-range,and high-resolution detection requirements.There have been few research reports on visible near-infrared and midinfrared dual-band large-angle spectroscopy.Therefore,this research has an important reference value for dual-band infrared detection and imaging technology.Methods The width and reflectance of the cut-off band at large angles were studied using the evaporation coating method.After practical calculation,it was concluded that at least four groups of film stacks should be used as the initial film system.A spectral curve that met the requirements could be obtained based on this optimization of the initial film system.The stress of ZnS film is generally compressive,while the stress of YbF_(3) film is generally tensile.The control variable method was used to optimize the deposition process and adjust the corresponding thickness to change the stress of the ZnS and YbF_(3) single-layer films.Because the film system was formed by depositing alternate layers of high and low refractive index materials,the tensile stress and compressive stress could offset each other.Therefore,the deformation of the substrate was smaller when the single-layer stresses of the high and low refractive index materials with corresponding thicknesses were closer.The film system structure was analyzed based on the measured stress results,which showed that the two sides of the film could offset each other and tended to be smaller in the design.Results and Discussions Based on a study of the characteristics of the high and low refractive index materials,the deposition process parameters of the film material(Table 2) were selected as the auxiliary parameters of the ion source(Table 3).Before coating,a constant temperature was 1 h.Thereafter,the ion source was used to clean the substrate for 15 min.A constant temperature of 200 ℃ was maintained for 2 h after coating,then the temperature was naturally cool to 90 ℃ for venting.The stress changes before and after coating are listed in Table 4.It can be seen from the analysis of the parameters before and after the process adjustment that the stress of the single-layer ZnS did not match that of the single-layer YbF_3.The ZnS and YbF_(3) deposition rates and auxiliary process parameters of the ion source were adjusted.The ZnS deposition rate was adjusted from 2 nm/s to 1.5 nm/s,and the deposition parameters of the YbF_(3) ion source was adjusted from 200 V and 5 A to 220 V and 5 A.After adjusting the process parameters,the stress of the single-layer ZnS was close to that of the single-layer YbF_3(Table 4).The antireflective film coated on the reverse side presented a tensile stress state,which could compensate for the stress on the spectral surface.The antireflective film coated on the reverse side met the requirements(Fig.6).The spectrum of the deposited film was obtained and analyzed(Fig.7),and the spectral data were imported into the film system design software for fitting.It was found that the actual thickness of the ZnS was 1.08 times the design thickness,and the actual thickness of the YbF_(3) was 0.95 times the design thickness.After adjusting the film thickness ratio,the transmission spectrum curve of the spectral surface after deposition(Fig.8) showed that the overall spectrum was well fitted with the design without obvious deviation(transmittance of 3.7-4.8 μm under the condition of the single-sided coating).The theoretical average transmittance in the band of 3.7-4.8 nm was 79.5%,and the average measured transmittance was 77%.The measured spectrum was fitted,and the fitting results showed that the spectral performance was not caused by the mismatch of the film thickness.After analysis,it was found that the addition of ion source-assisted deposition in the adjustment of the stress matching resulted in an increase in the absorption of the ZnS and YbF_(3) films but still met the technical specifications.Conclusions In this study,the temperature,deposition method,and ion source parameters were adjusted using the control variable method.The film stress was calculated using the Stoney formula.Then,the stresses of specific-thickness single-layer ZnS and YbF_(3were) adjusted to make these stresses match.When the stress of the antiantireflection surface was used to compensate for the stress of the spectral surface,the surface accuracy(PV value) of the spectral surface decreased from 0.63λ to 0.182λ.Then,the problem of the poor surface shape of the spectroscope could be solved.Based on a reverse analysis of the film deposition results,the film thickness was adjusted to improve the reflectivity and transmittance at an incidence of 55°.In the 0.6-0.9 μm wave band,the average reflectivity was 90.77%.In the 3.7-4.8 μm wave band,the average transmittance was 91.15%.The prepared film basically met the use requirements of the system components.
作者
付秀华
刘瑞奇
朱忠尧
韩克旭
王奔
刘俊岐
刘海成
Fu Xiuhua;Liu Ruiqi;Zhu Zhongyao;Han Kexu;Wang Ben;Liu Junqi;Liu Haicheng(School of OptoElectronic Engineering,Changchun University of Science and Technology,Changchun 130022,Jilin,China;Zhongshan Research Institute,Changchun University of Science and Technology,Zhongshan 528436,Guangdong,China;Beijing Institute of Space Mechatronics,Beijing 100094,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2023年第14期63-70,共8页
Chinese Journal of Lasers
基金
2022年度中山市第二批社会公益与基础研究项目(2022B2005)
“十三五”共用技术预研基金(41423060202)
长春市激光制造与检测装备科技创新中心资助项目(长科技合(2014219)号)。
关键词
光学器件
分光镜
微光夜视
中波红外成像
面形精度
optical devices
spectroscope
low light level night vision
medium wave infrared imaging
surface flatness
