基于液晶光阀的空间滤波特性

A Study of Spatial Filtering Characteristics Base on Liquid Crystal Light Valve

研究了在4f光学系统下空间滤波产生的条件,通过采用液晶光阀(LCLV)作为物平面,在波谱面上分别研究了低通滤波、高通滤波、方向滤波现象,并用CCD观测了输出图像。在低通滤波实验中,屏蔽了高频率的信息,从而使得原本边界十分清晰的网格变得模糊。在高通滤波实验中,屏蔽了低频率的信息,相对与周期排列的网格,留下的只是周期排列的高频的网格,与预期相符合。在方向滤波实验中,CCD接收的像与在像面上成的像为镜像关系,因此实验成功地实现了方向滤波。最后,分析了空间滤波器与输入平面周期的关系,以及光栅网格大小与滤波图象之间的关系。研究发现,对于同一滤波器,当网格间距超过一定限度的时候,横向方向上的信息将不能被屏蔽。

In this paper, the conditions of spatial filtering under 4f-optical-system are studied. Low pass filtering, high pass filtering and directional filtering are studied on the spectral plane by using LCLV as the object plane, and the output image is observed by CCD. In the low pass filtering experiment, the high frequency information is shielded, it makes the original boundary very clear grid become blurred. In the high pass filtering experiment, the information of low frequency is shielded, and the grid with periodic arrangement is relatively consistent with the expectation. In the direction filtering experiment, the image received by CCD and the image on the image surface are mirrored, so the experiment successfully realizes the directional filtering. Finally, the relationship between the spatial filter and the input plane period, and the relationship between the size of the grating mesh and the filtered image are analyzed. It is found that, for the same filter, when the spacing of the grid exceeds a certain limit, the information in the lateral direction will not be shielded.