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光子筛作为一种衍射光学元件,具有较大的色散,不适用于宽光谱成像。光子筛的焦距随着入射波长的增大而减小,而正的折射透镜焦距随着入射波长的增大而增大。应用了折衍混合方法进行光子筛消色差的设计。该设计利用二者相反的色散特性,在光子筛的一侧紧密放置一平凸透镜,从而实现光子筛的消色差设计。并针对可见光光谱进行了设计,分析表明该方法能够实现消色差,且具有一定校正二级光谱的能力,消色差波长与中心波长处焦距相对误差为0.33%,成像光谱带宽为20nm。与普通单个光子筛相比,该方法有效拓宽了光子筛的成像光谱范围。与使用波带片的折衍混合系统相比,聚焦光斑更小。
As a kind of diffractive optical element, photon sieve has larger dispersion and is not suitable for wide-spectrum imaging. The focal length of the photon sieve decreases with increasing incident wavelength, and the focal length of the positive refractive lens increases with increasing incident wavelength. The application of the diffraction and diffraction method for photonic sieve achromatic design. The design uses both the opposite dispersion characteristics, placed close to a plano-convex lens on one side of the photonic sieve to achieve achromatic design of the photonic sieve. The results show that this method can achieve achromaticity and has the ability to correct the secondary spectrum. The relative error between the achromatic wavelength and the center wavelength is 0.33% and the spectral bandwidth is 20 nm. Compared with the ordinary single photon sieve, the method effectively broadens the imaging spectral range of the photon sieve. The focal spot is smaller compared to a reticle mixing system that uses zone plates.