利用含二面角误差的角锥棱镜阵列实现反射光束均匀发散的方法

角锥棱镜常应用于光电跟踪、卫星通信、干涉仪等领域.在一些特殊应用场合中,要求经角锥棱镜反射的光束具有一定的发散角,以实现对距离激光器较远位置处探测器的覆盖.由于标准角锥棱镜不具备对光束发散的功能,本文利用含二面角误差的角锥棱镜对反射光束的不均匀发散特性,提出利用角锥棱镜阵列实现对反射光束均匀发散的方法和设计原则.采用衍射光学理论分析了所提方法及其设计原则的可行性,并依此设计了一个发散半角为0.5 mrad的角锥棱镜阵列.分析了光束参数、结构参数对反射光束远场衍射特性的影响,结果表明,入射光斑强度分布对反射光束发散半角没有影响,当角锥阵列满足点光源条件时,传输距离对反射光斑的角向均匀性没有影响;当阵元数超过一定值时,均匀性不再显著变化,但反射光斑的强度将进一步增加.在工程应用中,角锥棱镜阵列安装方位角误差对反射特性影响不显著,但角锥棱镜二面角的加工精度对反射特性影响较大,可通过进一步增加阵元数加以解决.

A method to diverge reflected beam uniformly using cube-corner retroreflector array with dihedral angle tolerances

The cube-corner retroreflector (CCR) is widely applied in the electro-optical tracking, satellite communication, interferometers and adjust-free solid state laser. In some applications, the incident beam emitted by a laser is reflected back by the CCR to a photoelectric detector. The distance between the photoelectric detector and the laser source on the ground is much larger than the diffraction-limited spot. Meanwhile, the attitude angle of the CCR would randomly vary for the jitter of the platform. Therefore, the reflected beam should be diverged uniformly at far-field, whereas the normal CCR cannot achieve the divergence on the reflected beam. The investigation indicated that six sub-spots are generated by a CCR with dihedral angle tolerances at far-field. According the characteristics of the CCR with dihedral angle tolerances, a structure and its design method are proposed to diverge the reflected beam with a CCR array. The azimuthal angles of the every CCR of the array should be specially designed to generate an annular and uniform pattern. Due to the propagation distance is much larger than the size of the CCR array, the feasibility of the method is analyzed by the wave theory. A CCR array with a divergence half-angle of 0.5 mrad is designed, in which the dihedral angle tolerance of every CCR is 20". The influences of the beam and structure parameters on the diffraction characteristics of the reflected beam are investigated. The numerical results indicate the divergence half-angle of the CCR array varies quasi-linearly with the change of the dihedral angle tolerance, and the intensity distribution of the incident beam does not influence the divergence half-angle. The propagation distance does not affect the uniformity of the reflected beam when the CCR array satisfies the point source condition. When the number of the array element increases to a certain value, the increase of the number can strengthen the intensity and hardly influences the uniformity of the reflected beam. For the restriction of the machining and assembling technics, the dihedral angle tolerance of every CCR is hardly identical and the assembling azimuthal angles of the array element can not be identical with the design result. Therefore, the influence of the assemblage azimuth error and machining accuracy of the dihedral angle are studied. It reveals that the assemblage azimuth error does not remarkably the reflection pattern, whereas the machining accuracy can observably affect the uniformity of the reflection pattern, which can be resolved by the growth of the number of array element.