Research On The Wide-angle Solar Blind UV Interference Filter

Because of the ozone strongly absorption of sunlight about 250 nm band of solar radiation,the UV band has a very week radiation near the ground after going through the atmosphere. The week band named solar blind region, and the solar blind ultraviolet detecting system has simple work background, so that solar blind ultraviolet detecting has more characteristics such as high sensitivity, low rate of false and simple construction than other kinds of detections. Solar blind filter is a critical component of solar blind detecting, it affects the performance of solar blind ultraviolet detecting system. We need solar blind ultraviolet detecting with high SNR and wide angle. But the transmission curve will get worse with the incidence angle increases. This essay point out that the key technology of wide angle solar blind filter is wide angle film design, on this basis, carry out research on material technics, coating design and plating.On the basis of the theory of coating design, this essay analyzed the relationship between depth and film material, and come up with a requirement of optical constant of film material. And on the basis of the requirement, technology experiment were finished, and optimum technology parameter were acquire. Essay also confirm the optical constant of film material, so that lay foundation for coating design.This essay also analyzed the problem that will rise when narrow band pass filters and cut-off filter used at oblique angle., such as short wave drift and worse of transformation curve. The drift distance of narrow band pass filters relates to the refractive index, to choose layer with high refractive index can reduce the drift distance; Worse of transformation curve of cut-off filters is caused by mismatch between different stacks. On the basis of theoretical analysis, designed wide-angle solar blind narrow bandpass filter with transmittance of 33%,available angle 60 ° and solar blind cut-off filter with transmittance of 40%,available angle 30°.Analyzed the importance of accuracy of thin film thickness monitoring while research the coating technology. The accuracy depend on tooling factor, and different kind of material through different techniques will have different tooling factor. Tested the tooling factor with optimum technology parameter, and coated solar blind filter with peak transmittance of 42%,stop band 290-400 nm, available angle 0-30°...