Research On Infrared Multispectral Camera Based On Array Filter

Multispectral imaging system can obtain the spatial structure information and spectral information of the target at the same time,which has a great application prospect in remote sensing monitoring and exploration,medical detection and diagnosis,military camouflage recognition,poison gas recognition,etc.Research of snapshot multispectral imaging system which has simple structure,small volume,light weight,suitable for portable,UAV and other light platforms is a new development direction in the field of photoelectric detection.In this paper,a staring snapshot infrared multispectral imaging system is studied in view of array filter and microlens array.Based on the existing spectrum-dividing and imaging technology,a long wave infrared multispectral imaging system with microlens array and array filter is proposed.The design and optimization of the system,the design and development of the microlens array structure and the array filter are finished,a 3×4(12)channel long wave infrared multispectral imaging system is built and the experimental verification research is carried out in this paper,which proves that the spectral response of the system is consistent with the blackbody standard radiation characteristics.The main research contents and results are as follows.(1)The multi-channel spectral imaging system which has the spectral range is 8-12?m,the number of channels is 12,the focal length is 80mm,the F number is 1.6,the total length is 103.5mm and the optical transfer function(MTF)of a single channel is greater than 0.1 at the Nyquist frequency of 42 lp/mm,which meets the imaging requirements had been obtained through the optimization design of ZEMAX.According to the design of the optical system,the structure of the microlens array and the array filter are designed.The microlens array structure with 3×4 arrays is obtained and the size and radius of curvature of a single microlens are 2.5×2.5mm and-1248.834 respectively.The size of the whole array and single channel of the filter are equal to the size of the microlens array.Each microlens array are corresponds to a spectral channel.(2)Two kinds of array filters were designed according to different principles.One was designed based on the filter characteristics of non transparent metal thin film with subwavelength structure.A 12 channel array filter(type A)with spectral resolution of about 300nm was designed in the range of 8-12?m by changing the structure parameters(period and diameter)of array micropres.The peak transmittance of each channel was about 70%.Another was based on the principle of Fabry Perot(F-P)interference.A 12 channel array filter(type B)is designed by changing the thickness of the spacer layer on the basis of 9?m single channel film system.The spectral resolution of the array filter is 40nm,the transmittance of each peak is 97%,the cut-off transmittance is less than 1%and the FWHM is 48nm.(3)Two kinds of filters were prepared by different methods.Due to the limitation of experimental equipment,the method of femtosecond laser,focused ion beam etching(FIB)and photolithography prepared A-type filter was not good,which could not meet the use requirements.The B-type filter was fabricated by the combined coating method,which is 9-9.5?m of the spectral range,the spectral resolution is about 30-60nm,the average peak transmittance is higher than 55%,the cut-off transmittance of each channel is lower than 1%and the position of the peak wavelength deviates from the designed peak wavelength by 20nm at most.(4)A 12 channel staring snapshot multispectral imaging system was built based on microlens array and array filter to carry out spectral imaging verification.Firstly,the calibration experiment of the system is completed by imaging the target in different temperature blackbody.Then the imaging experiments of electric soldering iron and halogen lamp are carried out respectively to verify the consistency of the spectral response of the system and the radiation characteristics of the standard blackbody.In this paper,a snapshot infrared multispectral camera based on array filter is designed and built,which can obtain clear and complete multispectral image of the target at the same time without the scanning devic.It realize the miniaturization and lightweight design of the imaging spectrometer.