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利用光学设计软件ZEMAX完成一款航天相机光学系统的设计,图5为航天相机光学系统结构图,光学系统是由主镜、次镜和三镜组成的离轴三反系统。相对孔径1∶2.4,视场10°×1°,系统像面大小211.59 mm×20.94 mm,其中X、Y和Z为光学坐标系。
首先对单镜组件进行装调,主镜、次镜和三镜组件的面形精度误差RMS分别为:0.061λ,0.050λ,0.059λ (λ为632.8 nm)。之后进行离轴三反光学系统的装调,根据像差理论将光学系统的波像差调整到最小。
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对上述光学系统进行像面测量,建立激光跟踪仪测量坐标系,如图6所示。坐标原点O为相机的安装孔投影到安装面的点,光轴指向探测器为Y′方向,垂直安装面方向为Z′方向,右手定则得到X′方向。
利用激光干涉仪测试光学系统中心视场成像质量,通过调节激光干涉仪,使干涉图为零条纹且Power值为零。将激光跟踪仪目标球固定在高精度六维调节架上,调节目标球,使其球心与激光干涉仪的焦点重合,干涉图为零条纹且Power值为零,此时目标球球心位置为光学系统中心视场焦点,激光跟踪仪记录该点坐标位置。焦点位置测试装置如图7所示。
通过调节标准平面镜和激光干涉仪确定光学系统各视场的焦点位置,激光跟踪仪记录各焦点位置的坐标。激光跟踪仪获得各视场的焦点空间坐标如表1所示。其中中心视场焦点在测量坐标系下的坐标为X′:−581.068 mm,Y′:−593.755 mm,Z′:141.462 mm。
表 1 激光跟踪仪测试数据
Table 1. Laser tracker test data
No. X′/mm Y′/mm Z′/mm 1 −689.141 −593.635 141.747 2 −674.485 −592.964 143.519 3 −660.163 −593.858 141.097 4 −645.744 −593.183 143.007 5 −631.403 −593.99 140.678 6 −617.007 −593.297 142.705 7 −602.635 −594.105 140.465 8 −588.276 −593.318 142.597 9 −581.068 −593.755 141.462 10 −573.882 −594.154 140.392 11 −559.526 −593.317 142.560 12 −545.132 −594.073 140.517 13 −530.763 −593.272 142.803 14 −516.355 −593.936 140.829 15 −501.998 −593.131 143.232 16 −487.578 −593.757 141.337 17 −473.396 −592.911 143.850 18 −674.640 −596.212 134.667 19 −645.853 −596.368 134.144 20 −617.074 −596.505 133.839 21 −588.290 −596.565 133.739 22 −559.488 −596.564 133.716 23 −530.676 −596.466 133.942 24 −501.865 −596.297 134.307 25 −473.220 −596.122 134.966 26 −688.913 −590.404 150.618 27 −660.023 −590.641 149.963 28 −631.310 −590.844 149.527 29 −602.582 −590.903 149.315 30 −573.894 −590.906 149.234 31 −545.187 −590.897 149.417 32 −516.452 −590.792 149.710 33 −487.739 −590.576 150.215 -
将主镜、次镜和三镜最后装调面形图.dat文件代入光学系统ZEMAX设计文件中,镜子曲率半径、厚度、离轴量等参数均为实测值,图9为面形代入前后光学系统波前图。
代入镜子实际面形后的光学系统,像面的分布情况会发生变化,用ZEMAX分别对各个视场进行分析,得出每个视场在光学坐标系下对应的焦点坐标,如表2所示。
表 2 ZEMAX理论像面焦点坐标
Table 2. Focus coordinates of ZEMAX ideal image plane
No. X/mm Y/mm Z/mm 1 −104.986 0.000 −31.067 2 −83.912 0.000 −31.060 3 −62.889 0.000 −31.065 4 −41.905 0.000 −31.052 5 0.000 0.000 −31.050 6 41.905 0.000 −31.051 7 62.889 0.000 −31.062 8 83.912 0.000 −31.058 9 104.986 0.000 −31.063 10 −104.986 −10.472 −31.067 11 −83.912 −10.472 −31.068 12 −62.889 −10.472 −31.07 13 −41.905 −10.472 −31.064 14 0.000 −10.472 −31.061 15 41.905 −10.472 −31.063 16 62.889 −10.472 −31.066 17 83.912 −10.472 −31.065 18 104.986 −10.472 −31.065 19 −104.986 −5.236 −31.068 20 0.000 −5.236 −31.055 21 104.986 −5.236 −31.065 22 −104.986 5.236 −31.064 23 0.000 5.236 −31.038 24 104.986 5.236 −31.06 25 −104.986 10.472 −31.059 26 −83.912 10.472 −31.048 27 −62.889 10.472 −31.054 28 −41.905 10.472 −31.034 29 0.000 10.472 −31.024 30 41.905 10.472 −31.033 31 62.889 10.472 −31.052 32 83.912 10.472 −31.045 33 104.986 10.472 −31.056 -
将图8所示的实际像面与图10所示的ZEMAX输出的理想像面进行对比分析。在测量坐标系下,实测像面偏移量分别为Δx:0.12 mm、Δy:0.09 mm、Δz:0.10 mm,实测像面平面度0.049 mm,理论像面平面度0.040 mm,偏差0.009 mm,两个像面形状吻合性较好。根据获得的实测像面位置,在相机总装模型上进行探测器模拟匹配,仿真结果显示,探测器达到最佳位置时,机械接口完全可以匹配。以上测量和仿真结果说明光学系统已装调到位,可开展后续工作。
Measurement technology of image plane of wide-field space camera
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摘要: 宽视场高质量的航天相机是未来有效载荷的发展方向,基于宽视场航天相机的装调需求,提出了一种干涉测量与几何量测量相结合的像面测量方法。搭建了宽视场航天相机像面测量平台,利用激光干涉仪确定各视场的焦点位置,激光跟踪仪获取各焦点位置坐标,通过坐标换算和拟合完成像面的绘制,像面测量误差可控制在0.01 mm内。通过该方法,完成了一款离轴三反航天相机的像面绘制,系统焦距1200 mm,相对孔径1∶2.4,视场角10°×1°。测试的像面与光学设计软件ZEMAX输出的理想像面进行比对,像面形状及位置基本吻合,平面度偏差0.009 mm。测试结果表明光学系统装调到位,为探测器配准工序的完成提供了重要依据。Abstract: Wide-field and high-quality space camera is the future development direction of payload. Based on the alignment requirements of the wide-field space camera, an image plane measurement method combining interferometry and geometric measurement was proposed. The image plane measurement platform of the wide-field space camera was built. A laser interferometer was used to determine the focal position of each field of view and a laser tracker was used to obtain the coordinates of each focal position in this method. Finally, the image plane was drawn through coordinate conversion and fitting. Image plane measurement error could be controlled within 0.01 mm. Through this method, the image plane drawing of off-axis three-mirror reflective space camera was completed, the system was with a focal length of 1200 mm, a F-number of 2.4, a linear field of view of 10°×1°. The test image plane was compared with the ideal image plane output by the optical design software ZEMAX, the shape and position of the image plane were basically consistent, and the flatness deviation was at 0.009 mm. The test results show that the optical system is aligned in place, and it provides an important basis for the completion of the detector registration process.
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表 1 激光跟踪仪测试数据
Table 1. Laser tracker test data
No. X′/mm Y′/mm Z′/mm 1 −689.141 −593.635 141.747 2 −674.485 −592.964 143.519 3 −660.163 −593.858 141.097 4 −645.744 −593.183 143.007 5 −631.403 −593.99 140.678 6 −617.007 −593.297 142.705 7 −602.635 −594.105 140.465 8 −588.276 −593.318 142.597 9 −581.068 −593.755 141.462 10 −573.882 −594.154 140.392 11 −559.526 −593.317 142.560 12 −545.132 −594.073 140.517 13 −530.763 −593.272 142.803 14 −516.355 −593.936 140.829 15 −501.998 −593.131 143.232 16 −487.578 −593.757 141.337 17 −473.396 −592.911 143.850 18 −674.640 −596.212 134.667 19 −645.853 −596.368 134.144 20 −617.074 −596.505 133.839 21 −588.290 −596.565 133.739 22 −559.488 −596.564 133.716 23 −530.676 −596.466 133.942 24 −501.865 −596.297 134.307 25 −473.220 −596.122 134.966 26 −688.913 −590.404 150.618 27 −660.023 −590.641 149.963 28 −631.310 −590.844 149.527 29 −602.582 −590.903 149.315 30 −573.894 −590.906 149.234 31 −545.187 −590.897 149.417 32 −516.452 −590.792 149.710 33 −487.739 −590.576 150.215 表 2 ZEMAX理论像面焦点坐标
Table 2. Focus coordinates of ZEMAX ideal image plane
No. X/mm Y/mm Z/mm 1 −104.986 0.000 −31.067 2 −83.912 0.000 −31.060 3 −62.889 0.000 −31.065 4 −41.905 0.000 −31.052 5 0.000 0.000 −31.050 6 41.905 0.000 −31.051 7 62.889 0.000 −31.062 8 83.912 0.000 −31.058 9 104.986 0.000 −31.063 10 −104.986 −10.472 −31.067 11 −83.912 −10.472 −31.068 12 −62.889 −10.472 −31.07 13 −41.905 −10.472 −31.064 14 0.000 −10.472 −31.061 15 41.905 −10.472 −31.063 16 62.889 −10.472 −31.066 17 83.912 −10.472 −31.065 18 104.986 −10.472 −31.065 19 −104.986 −5.236 −31.068 20 0.000 −5.236 −31.055 21 104.986 −5.236 −31.065 22 −104.986 5.236 −31.064 23 0.000 5.236 −31.038 24 104.986 5.236 −31.06 25 −104.986 10.472 −31.059 26 −83.912 10.472 −31.048 27 −62.889 10.472 −31.054 28 −41.905 10.472 −31.034 29 0.000 10.472 −31.024 30 41.905 10.472 −31.033 31 62.889 10.472 −31.052 32 83.912 10.472 −31.045 33 104.986 10.472 −31.056 -
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