Design And Preparation Technology Of Multi-channel Narrow Band Filter

Multispectral and hyperspectral imaging have the advantages of both imaging and spectral detection.It is widely used in remote sensing,hydrometeorology,medical,and military target reconnaissance.Multi-channel narrow band filters are the core spectral components of multispectral imaging systems.Therefore,the development of integrated multi-channel narrow band filters is the main way to improve the performance of multi-spectral imaging systems.In this paper,a nanoimprint method and a combined mask method were used to prepare a 10×10array multi-channel narrow band filter,respectively.Which includes the design of central wavelength gradient film system,material optimization and process optimization,cavity control,and test verification were studied.The results are as follows:(1)Optimal design of F-P filter.Based on the F-P principle,a narrow band filter film system with a central wavelength gradient in the visible band and the near-infrared band is designed.The film structure is G|(LH)~5(4L)(HL)~5|A and G|(LH)~6(4L)(HL)~6|A,respectively.In addition,the 10 spectral channels are designed based on a single channel.The average peak transmittance is greater than 90%,and the average half width of the passband(FWHM)is about10 nm.(2)Film material and process optimization.The coating materials are optimized,the thin film material plating process is studied and the best process parameters are obtained.The special tooling fixtures required for thin film plating are designed.The designed film system is tested,and the preparation of the 10×10 array narrow band filter is completed.(3)Discontinuous regulation of cavity thickness.Designed and prepared 5×5?10×10array embossing hard molds respectively,which were transferred to PDMS soft molds.The NOA73 UV-curable optical adhesive is preferably a spacer film material.The optimal process parameters are determined through experiments,and the optical characteristics of the spacer film and the transfer of embossed patterns are completed.(4)Test verification.Design and set up a micro test system to test the samples.In the550?650nm band,the average peak transmittance of the 10×10 array narrow band filter channel is 94%,the average FWHM is 9.7nm,and the cut off transmittance is less than 1%.In the650?750nm band,the average peak transmittance is 94.7%,the FWHM is 10nm,and the cut off transmittance is less than 1%.The peak transmittance in the near infrared region is 88.6%,the FWHM is 12nm,and the cut off transmittance is less than 3%.Test results meet the expected indicatorsThe research found that the main reasons affecting the narrow band peak transmittance and other indicators are:the use of a single crystal monitoring results in the cumulative amplification of single-layer film thickness errors;the roughness of the hard mold surface is large;the surface of the hard mold is spherical.According to the spectrum test results,it is known that the nanoimprinting method for preparing narrow band filters is feasible.Error control and process optimization are the directions for further research.