研究了螺旋型波带片的成像特性。螺旋型波带片是一种新型成像元件,能够实现光学希尔伯特变换,获取边缘增强图像。采用快速傅里叶变换算法对螺旋型波带片的成像进行了数值模拟,分析了其成像特性并实验进行验证。通常螺旋型波带片作为空间滤波器要求物距满足夫琅禾费(Fraunhofer)衍射条件,理论计算表明在某些菲涅耳(Fresnel)衍射区域内螺旋型波带片仍可获得良好的成像效果,因此螺旋型波带片的实际视场比根据夫琅禾费衍射条件限定的视场要大。实验结果与数值模拟的吻合很好。因此利用快速傅里叶变换算法对螺旋型波带片成像质量模拟可以有效评估成像质量,对螺旋波带片显微镜的设计有重要的指导意义。

The imaging performance of spiral zone plates is studied. Spiral zone plate is a new imaging optic device which can implement optical Hilbert transform and produce the edge-enhanced imaging of an object,is presented. The performance of spiral zone plates is numerically analyzed using fast Fourier transform and the working condition of spiral zone plates is studied by the numerical calculation. It is generally considered that the distance between the object and the optics should meet the Fraunhofer diffraction using the spiral zone plate as the spatial filter. The numerical analysis shows that the spiral zone plate still works well in some Fresnel diffraction region. It means that the actual field of view is larger than that restricted by the Fraunhofer diffraction. The experimental results show good agreements with theoretical simulation. The method of fast Fourier transform can effectively evaluate the imaging performance of spiral zone plates and provide an important guide to the design of the spiral zone plate microscope.