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首页> 外文期刊>Astronomy and astrophysics >Active optics methods for exoplanet direct imaging - Stress polishing of supersmooth aspherics for VLT-SPHERE planet finder
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Active optics methods for exoplanet direct imaging - Stress polishing of supersmooth aspherics for VLT-SPHERE planet finder

机译：系外行星直接成像的主动光学方法-VLT-SPHERE寻星器的超光滑非球面应力抛光

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Context. The next generation of exoplanet hunters will be targeting hot Jupiter-like exoplanets orbiting around nearby stars through direct imaging. The high contrast needed for such planet finders requires optical surfaces free of high spatial frequency ripples that might remain in the post-coronagraphic image as quasi-static speckles. Aims. We report results on the manufacturing of three supersmooth aspherical mirrors for the ESO/VLT-SPHERE instrument. The excellent optical quality obtained will allow the future planet hunter to increase the level of achievable contrast by a strong reduction of the noise level and residual quasi-static speckles on the image plane. Methods. The stress polishing method used on these mirrors is well suited to superpolishing aspheric components for astronomy. The main advantage of this technique is the very high optical quality obtained either on the form errors or on the high spatial frequency errors. Furthermore, the roughness can be decreased to a few angstroms, thanks to the classical polishing with a large pitch tool. Results. Interferograms obtained during polishing and in the final stage show the supersmooth quality of each mirror. Errors in the high spatial frequency range are lower than 4?nm rms WF, thereby avoiding the degradation of the post-coronagraphic image. A comparison of the power spectral density (PSD) obtained by stress polishing and the PSD of the VLT-UT3 primary mirror demonstrates that the contrast capabilities will not be limited by the aspherical mirrors.
机译：上下文。下一代系外行星猎人将瞄准通过直接成像在附近恒星周围运行的类似木星的热系外行星。这样的行星发现者所需的高对比度要求光学表面没有高空间频率波动，该波动可能会在冠状动脉造影后图像中保留为准静态斑点。目的我们报告了ESO / VLT-SPHERE仪器的三个超光滑非球面镜的制造结果。所获得的出色光学质量将使未来的星球猎人能够通过大幅降低噪声水平和像面上的残留准静态斑点来提高可达到的对比度水平。方法。这些反射镜上使用的应力抛光方法非常适合对天文学非球面组件进行超抛光。该技术的主要优点是在形状误差或在高空间频率误差上获得的非常高的光学质量。此外，由于使用了大间距工具进行的经典抛光，粗糙度可以降低到几埃。结果。在抛光过程中和最终阶段获得的干涉图显示了每个反射镜的超光滑质量。高空间频率范围内的误差小于4？nm rms WF，从而避免了冠状动脉造影后图像的退化。通过应力抛光获得的功率谱密度（PSD）与VLT-UT3主镜的PSD的比较表明，对比能力将不受非球面镜的限制。

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