A novel optical element, combined triangular-section prism, for generating non-diffracting line-structured beam is proposed. This element is designed with gluing positive and negative isosceles triangular-section prisms. Its property is the same as the single positive isosceles triangular-section prism for beam transformation, and the equivalent bottom corner is decided by the bottom corner difference of positive and negative isosceles triangular-section prisms. Therefore, we can get smaller bottom corner by combining the positive and negative i-sosceles triangular-section prisms with comparatively large bottom corner for each triangular-section prism, and also get the non-diffracting line-structured beam with larger focus depth. The technical problem of the small bottom corner which is hard to machine is solved. The formation mechanism of the non-diffracting line-structured beam is analyzed by geometrical optics, and the relevant parameters are calculated. The intensity distribution is simulated by diffraction and interference theories. The results show that the non-diffracting line-structured beam is formed with large depth of focus at normal incidence of plane waves.%提出一种可产生无衍射线结构光的新型光学元件——组合三角棱镜,由正、负等腰三角棱镜胶合在一起设计而成,其变换光束特性与单个正等腰三角棱镜相同,等效底角由正、负等腰三角棱镜底角之差决定,因此可通过较大底角的正、负等腰三角棱镜组合得到更小角度的底角,以获得更大焦深的无衍射线结构光,解决了单个正等腰三角棱镜小角度加工困难的技术问题.采用几何光学理论分析产生无衍射线结构光的原理,计算无衍射线结构光的相关参数,由衍射积分理论分析和模拟光束经过新型光学元件后的光强分布特性.实验结果表明:平面波正面入射新型光学元件可以产生具有大焦深的无衍射线结构光.
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