用于产生空心焦场的二元环带相位板

Binary Annular Phase Plate Used to Generate Hollow Focal Field

基于标量衍射理论,利用相干叠加的方法,研究了可以产生空心焦场的二元环带相位板。推导了各环带半径应满足的解析表达式,通过数值计算研究了环带半径对空心焦场的影响规律。研究结果表明,在焦平面上,相位板环带半径对旁瓣比和最大光强比的影响较大,对空心焦场半径的影响较小,增加环带数能够减小旁瓣比,增大最大光强比。在轴向上,环带数增加并不能增大最大光强比,环带数和环带半径对旁瓣比和最大光强比的影响较大。对于二元环带相位结构,旁瓣比和最大光强比仅取决于环带半径,和数值孔径无关;在焦面上,空心焦场半径和数值孔径成反比,在轴向上,空心焦场半径和数值孔径的平方成反比。

Based on the scalar diffraction theory,a binary annular phase plate is studied by means of the coherent superposition method,which is used for the generation of a hollow focal field.The analytical expression of the radius for each ring is derived.The influence law of the ring radius on the hollow focal field is also investigated by the numerical calculation method.The research results show that,in the focal plane,the ring radius of this phase plate has a great influence on the side lobe ratio and the maximum light intensity ratio,but has a little influence on the radius of the hollow focal field.The increase in the number of rings reduces the side lobe radio,but increases the maximum light intensity ratio.In contrast,in the axial direction,the increase in the number of rings cannot increase the maximum light intensity ratio.Both the number of rings and the ring radius have relatively great influence on the side lobe ratio and the maximum light intensity ratio.For a binary annular phase structure,the side lobe ratio and the maximum light intensity ratio only depend on the ring radius and are independent of numerical aperture.In the focal plane,the radius of the hollow focal field is inversely proportional to the numerical aperture.In the axial direction,the radius of the hollow focal field is inversely proportional to the square of numerical aperture.