Robotilter: an automated lens/CCD alignment system for the Evryscope
Robotilter: an automated lens/CCD alignment system for the Evryscope
复制标题
Robotilter：用于 Evryscope 的自动镜头/CCD 对准系统
DOI：
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发表时间：
2020
影响因子：
2.3
通讯作者：
D. del Ser
中科院分区：
文献类型：
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作者：
J. Ratzloff;N. Law;H. Corbett;O. Fors;D. del Ser
抽象的。由于相机镜头具有高性能、传统望远镜光学器件无法达到的宽视场 (FOV) 以及适中的成本，因此越来越多地用于宽视场天文观测。商用光学系统的加工和装配公差会导致镜头和 CCD 之间出现轻微的未对准（倾斜），从而导致点扩散函数 (PSF) 下降。我们构建了一个自动对准系统 (Robotilters) 来解决这一挑战，在紧凑且低成本的封装中优化四个自由度：两个倾斜轴、一个分离轴（CCD 和镜头之间的距离）和镜头焦点（通过转动镜头聚焦环实现镜头的内置焦点，从而使光学元件相对移动）。 Robotilters 消除了倾斜并优化了亚 10 μm 级别的焦点，完全自动化，运行时间约为 2 小时，并且一旦对准即可保持稳定多年。 Robotilters 是为 Evryscope 望远镜（一个 780-MPix 22 相机阵列，具有 8150 平方度的 FOV 和连续 2 分钟的节奏）建造的，旨在同时探测极大天空区域中的短时尺度事件。整个图像场的质量差异，尤其是与中心相比的角落和边缘，是像 Evryscope 这样的宽视场天文勘测中的一个重大挑战。在这种情况下，单个星点扩散函数（通常仅延伸几个像素）非常容易受到光学像差轻微增加的影响。对于典型的 Evryscope 相机，Robotilter 解决方案将图像中心的极限幅度提高了 0.5 mag，在角落提高了 1.0 mag，失真更小，PSF 更小（在许多情况下是角落和边缘范围的一半）。我们描述了 Robotilter 机械和软件设计、相机对准结果、长期稳定性和图像改进。还探讨了在广域天文调查中普遍使用的潜力。
Abstract. Camera lenses are increasingly used in wide-field astronomical surveys due to their high performance, wide field-of-view (FOV) unreachable from traditional telescope optics, and modest cost. The machining and assembly tolerances for commercially available optical systems cause a slight misalignment (tilt) between the lens and CCD, resulting in point spread function (PSF) degradation. We have built an automated alignment system (Robotilters) to solve this challenge, optimizing four degrees of freedom—two tilt axes, a separation axis (the distance between the CCD and lens), and the lens focus (the built-in focus of the lens by turning the lens focusing ring, which moves the optical elements relative to one another) in a compact and low-cost package. The Robotilters remove tilt and optimize focus at the sub-10-μm level, are completely automated, take ≈2 h to run, and remain stable for multiple years once aligned. The Robotilters were built for the Evryscope telescope (a 780-MPix 22-camera array with an 8150-sq. deg FOV and continuous 2-min cadence) designed to detect short-timescale events across extremely large sky areas simultaneously. Variance in quality across the image field, especially the corners and edges compared to the center, is a significant challenge in wide-field astronomical surveys like the Evryscope. The individual star PSFs (which typically extend only a few pixels) are highly susceptible to slight increases in optical aberrations in this situation. The Robotilter solution resulted in a limiting magnitude improvement of 0.5 mag in the center of the image and 1.0 mag in the corners for typical Evryscope cameras, with less distorted and smaller PSFs (half the extent in the corners and edges in many cases). We describe the Robotilter mechanical and software design, camera alignment results, long-term stability, and image improvement. The potential for general use in wide-field astronomical surveys is also explored.