从理论和实验上探讨了体光栅在垂直方向的角度选择性，根据ｋ矢量球与参考点源平面上的对应关系，导出了垂直方向的选择角，并得到光栅简并线方程。实验结果表明体光栅在垂直方向具有有限的选择角。

The vertical angular selectivity of volume holographic gratings in photorefractive crystals is investigated theoretically and experimentally. The vertical selective angle and the shape of the grating degeneracy line are derived by using a simplified geometrical model relating the k vector sphere to the reference point plane. The study shows that volume gratings have finite selectivity in vertical direction, so that grating degeneracy does not occur along vertical lines.