设计并采用微细加工技术制作了直径D=50mm,特征尺寸为10μm的大口径多孔透镜(photon sieve)。在一定的视场下采用数值计算和实验方法分析了其聚焦特性和MTF曲线,为克服多孔透镜一级衍射效率较低,成像质量受背景光干扰的影响,采用了同轴和离轴成像实验。实验结果与聚焦特性一致,两种实验方法得出的不同实验结果表明:离轴成像系统效果克服了同轴成像受0级背景光的影响,改善了像质,为很多一级衍射效率较低的衍射透镜成像提供一种新的成像方式。
A photon sieve with parameter of diameter D=50 mm minimum microhole diameter of 10um formed on a layer of metal film supported by a piece of thin glass, was designed and fabricated by means of microfabrication technique. Both focus spot and MTF curves were presented and analyzed in certain View of Field (VOF) in simulated and experimental ways to evaluate its imaging characteristics. Off-axis imaging experiments were carried out using the element to improve the imaging quality, and on-axis imaging experiment is done for comparison. The results show focus spot was in excellent agreement with simulated value and off-axis imaging are better than that of on-axis imaging by getting over the blurry effect caused by the 0-order diffractive wave on background, which could offer a new imaging method for this lens with less energy of 1^st-order diffraction.