由于截止滤光片具有的良好光学特性, 分别给出了基于两片长波通和两片短波通截止滤光片的光束空间低通滤波装置。利用几何光学法, 分别研究了这两种装置对光束的一维空间低通滤波特性, 结果表明: 这两种滤波装置的角谱选择性带宽与滤光片过渡带的带宽以及两滤光片的夹角有关。对于长波通滤光片, 两滤光片的夹角要大于等于截止角度的2倍, 而对于短波通滤光片, 两滤光片的夹角要小于等于截止角度的2倍, 理论上得出这两种装置的半高宽度的角谱选择性带宽均等于过渡带的宽度结论, 此时两滤光片之间的夹角为截止角度的2倍。

Due to the fine optical characteristics of cutoff filter, the configurations based on two pieces of long-pass cutoff filter or two pieces of short-pass cutoff filter were put forward respectively. Based on the geometrical optics, the performances of these two configurations were analyzed. The results show that the angular spectrum bandwidths of these two configurations depend on both the intersection angle between the cutoff filters and the angular bandwidth of transition zone. For the long-wave-pass cutoff filter, the intersection angle must be no less than two times of its cutoff angle. While for the short-wave-pass cutoff filter, the intersection angle must be no more than two times of its cutoff angle. Theoretically, its minimum bandwidth is equal to the angular bandwidth of transition zone, when the intersection angle is two times of the cutoff angle.