光子筛透镜组合的折衍混合消色差系统设计

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。

Hybrid Refractive-Diffractive Achromatic System Design with Photon Sieve-Lens Combination

Photon sieve is a diffractive optical element with large chromatic aberration, which is not suitable for imaging in wide spectral. The focal length of photon sieve decreases when the incident wavelength increases, while the focal length of positive refractive lens increases when the incident wavelength increases. The design applying the method of hybrid refractive-diffractive into the photon sieve achromatic is proposed. These opposite dispersive characteristics are used in this method. A plano-convex len is placed close to side of a photon sieve in order to achieve achromatic design. Then the achromatic system is designed in the visible spectrum. The analysis shows that the system is achromatic and has a certain ability of secondary spectrum correction. The relative error between focal lengths of achromatic wavelength and centre wavelength is 0.33%. The imaging spectral bandwidth is 20 nm. Compared with ordinary single photon sieve, the design broadens the imaging spectrum range. Compared with the hybrid refractive-diffractive system using zone plate, a smaller focusing spot can be achieved.