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合理的光学结构有助于在校正像差的同时,兼顾体积、质量、性价比等问题。共口径光学系统在设计之初一般会规定体积大小、系统长度和系统焦距等参数。笔者取系统焦距
$f = 1\;500\;{\rm{mm}}$ ,两镜间隔$d = $ $ 300\;{\rm{mm}}$ ,遮挡比$\alpha = 0.34$ 。由公式(1)、(2)、(5)得${R_1} = $ $ - 909.090\;909\;{\rm{mm}}$ ,${R_2} = - 443.478\;261\;{\rm{mm}}$ ,$\;\beta = - 3.3$ 。对以上讨论的几种类型光学系统的非球面系数${k_1}$ 、${k_2}$ 进行计算,计算结果如表1所示。Type of optical system Cassegrain Dall-kirkham Pressmann-Camichel Ritchey-chretien Aspheric coefficient (k1) −1.000 000 −0.597 652 0.000 000 −0.905 390 Aspheric coefficient (k2) −3.495 274 0.000 000 5.191 917 −4.317 169 Table 1. Aspheric coefficients of mirrors for various optical systems
对上述几种光学系统进行计算优化,得到优化后得光学结构参数,如表2所示。经过光学软件得优化结果与计算结果对比,可以发现两种求解方式光学参数一致,说明笔者的计算结果和软件优化结果一致,上述计算方法精准便捷。
Type of optical system Cassegrain Dall-kirkham Pressmann-Camichel Ritchey-chretien R1/mm −909.090 910 −909.090 903 −938.599 510 −909.090 909 R2/mm −443.478 261 −443.478 276 −455.281 951 −443.756 312 d 299.999 999 299.999 992 312.880 016 299.903 103 k1 −1.000 000 −0.597 777 0 −1.092 489 k2 −3.495 274 0 5.602 234 −4.298 315 β −3.300 000 −3.300 000 −3.196 251 −3.300 000 α 0.340 703 0.339 795 0.331 827 0.341 195 Table 2. Optimization results of optical structure parameters
Initial structure solution of Cassegrain type transceiver optical antenna for laser communication and imaging
doi: 10.3788/IRLA20210173
- Received Date: 2021-03-12
- Rev Recd Date: 2021-04-20
- Publish Date: 2022-04-07
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Key words:
- laser communication /
- occlusion ratio /
- Cassegrain antenna /
- solving method of initial structure
Abstract: In the laser communication and imaging system, whether the Cassegrain type optical antenna is used as a laser signal transceiver or an optical imaging device, the existence of aberrations will inevitably influence its signal intensity and imaging quality. By analyzing optical antenna of the third-order aberration theory and the perturbation theory, according to the relationship between the antenna gain factor and the occlusion ratio, a convenient and fast method for solving the Cassegrain type optical antenna structure was proposed. This method can not only consider the efficiency of the optical antenna, but also meet the requirements of the volume size and aberration of the optical system design. Especially in the case that only knowing the focal length of the optical system, the distance between the primary and secondary mirrors, the occlusion ratio, the structural parameters of the optical antenna can be calculated quickly. Not only gives the calculation formulas of the optical structure parameters for four types Cassegrain optical antennas, but also explains the advantages and disadvantages in the different application. According to comparing the calculation results of four typical optical antennas with the optimal results, the results show that this method is a convenient, fast and accurate method to solve the Cassegrain type optical antenna structure, and has practical significance in engineering.