Wang Jikang, Zhang Wuhong, Qi Qianqian, Zheng Shasha, Chen Lixiang
Department of Physics and Laboratory of Nanoscale Condensed Matter Physics, Xiamen University, Xiamen 361005, China.
Sci Rep. 2015 Oct 29;5:15826. doi: 10.1038/srep15826.
In the spiral phase contrast imaging, the integer spiral phase plate (SPP) are generally employed to perform the radial Hilbert transform on the object. Here we introduce fractional SPP filters, instead of the integer ones, to investigate the gradual formation of edge enhancement for pure phase objects. Two spatial light modulators are used in our experimental configuration. One is addressed to display the pure phase object of a five-pointed star, while the other serves as a dynamic filter of fractional topological charge Q. Of interest is the observation of the complete reversal of the edge and background brightness by gradually changing the fractional vortices from Q = 0 to 1. The experimental results were well interpreted based on the OAM spectra of fractional SPP, which indicates that the filtered output image can be considered as a coherent superposition of all possible images that are individually resulted from the integer OAM filtering. Besides, we show that the spiral phase contrast effect can still be observed in real time for a rotating three-leaf clover. Our results may find potential applications in the optical microscopic imaging.
在螺旋相位对比成像中，通常采用整数螺旋相位板（SPP）对物体进行径向希尔伯特变换。在此，我们引入分数阶SPP滤波器而非整数型的，以研究纯相位物体边缘增强的逐渐形成过程。在我们的实验配置中使用了两个空间光调制器。一个用于显示五角星的纯相位物体，另一个用作分数拓扑电荷Q的动态滤波器。有趣的是，通过将分数涡旋从Q = 0逐渐改变到1，可以观察到边缘和背景亮度的完全反转。基于分数阶SPP的轨道角动量（OAM）光谱对实验结果进行了很好的解释，这表明滤波后的输出图像可以被视为由整数OAM滤波单独产生的所有可能图像的相干叠加。此外，我们表明对于旋转的三叶苜蓿仍可实时观察到螺旋相位对比效应。我们的结果可能在光学显微成像中找到潜在应用。
