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通过平像面拼接排列的方法使各子眼一次像面中心点排列在同一平面上。整体复眼系统由两部分构成:曲面复眼透镜阵列和中继系统。系统的总视场角为96°,长度为84 mm,系统工作波长为0.4~0.9 μm。单子眼的视场为16°,由两片透镜组成。优化后的光学中继系统由九片透镜组成,焦距为5 mm,视场角为120°。在进行系统组合设计时要注意光瞳匹配原则,曲面复眼透镜阵列的出瞳位置应是光学中继系统的入瞳位置。组合后系统的像差主要由中继系统决定,系统的光阑位置位于中继系统的中间位置处。最终系统设计参数如表1所示。
Design objective Standard requirement Acceptance angle of each
ommatidium 2α/(°)16 Number of ommatidia n 11 Focal length of relay system/mm 5 Diameters of relay system D/mm 3 Total FOV of the system $ \theta $/(°) 96 Wavelength range λ/μm 0.4-0.9 Focal length f/mm 0.5 Table 1. Optical parameters of compound eye system with large field of view
系统组合后的总体视场角为96°,目标在中心和边缘部分都能清晰成像,并且相关像差得到校正。曲面复眼系统整体布局如图6所示。
由于弯曲复眼中所有子眼全部对称排列,仅选取中心子眼和最边缘子眼进行分析。图7(a)为中心子眼的场曲和畸变图,可以看出场曲小于0.1 mm,畸变小于1%,满足大部分应用的成像要求。图7(b)为中心子眼的点列图,可以看出RMS值均在艾里斑半径内,说明像质满足一定要求。图7(c)为中心子眼的MTF曲线图,可以看出在80 lp/mm的奈奎斯特频率下,MTF值接近0.6,表明可以获得较好的成像质量。图7(d)为中心子眼波前图,可以看出波峰到波谷为0.086λ,成像质量满足要求。
Figure 7. Simulation results for central ommatidium. (a) Field curvature and distortion; (b) Spot diagram; (c) MTF; (d) Wavefront
图8为最边缘子眼的模拟结果。图8(a)为最边缘子眼在ω=40°(即子眼透镜偏向光中继系统光轴的夹角为40°)的场曲畸变曲线图。可以看出,最边缘子眼场曲小于0.2 mm,畸变控制在2%以内。图8(b)为最边缘子眼的点列图,不同视场下的RMS值分别为3.106、2.693、2.694、3.699、3.686 μm,艾里斑半径为4.606 μm,RMS值均在艾里斑半径内。最边缘子眼的MTF曲线图如图8(c)所示,可以看出在80 lp/mm的奈奎斯特频率下,MTF值高于0.4且曲线平滑,表明在边缘视场也可以获得较好的成像质量。图8(d)为最边缘子眼的波前图,可以看出波峰到波谷为0.424λ,说明最边缘子眼产生的最大光程差得到了很好的校正。
Large field of view flat image plane splicing method for compound eye systems
doi: 10.3788/IRLA20210848
- Received Date: 2021-11-12
- Rev Recd Date: 2021-12-21
- Publish Date: 2022-08-05
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Key words:
- optical systems design /
- bionic compound eye system /
- flat plane splicing /
- curved plane splicing
Abstract: The conventional curved bionic compound eye relay system is required to undertake the task of converting the curved image plane caused by the splicing of large-field subeyes into a flat image field, which poses certain difficulties to the system design. A method was proposed for the splicing arrangement of the flat image plane of the large-field compound eyes, and the method was described mathematically. By constructing a balanced model between the number of subeyes, the total field of view of the system and the subsequent reasonable selection of the optical relay system parameters, the relationship between the depth of field of the relay system and the optical range difference of the spliced image plane of the compound eye was analysed, and it was concluded that the optical range difference generated by the splicing method of the compound eye flat image plane was within the acceptable depth of field of a typical optical relay system, which could effectively reduce the design pressure of the relay optical system. Based on the above theory, a compound eye optical system with a field of view of 16° for a single subeye and an overall field of view of 96° was designed for practical verification. The system finally achieves an aberration of less than 2%, the transfer function reaches the diffraction limit in the central field of view and the edge field of view is close to the diffraction limit with good image quality, which proves that splicing theory is feasible.