Development of Rapid Active Figure Control Systems for Large Telescope Mirrors

国家天文台计划在夏威夷莫纳克亚山顶建造一座8米长的光学和红外天文望远镜(日本国家大望远镜：JNLT)。JNLT将使用带有主动光学系统的薄弯月面主镜，以合理的成本获得最佳成像质量。用于提高JNLT成像质量的另一项重要创新是自适应光学系统。测量了大气湍流引起的波前像差，并用快速自适应光学元件对其进行了快速补偿。本文的研究成果如下：(1)建立了62 cm工程望远镜主动光学系统的闭环自动控制系统。(2)通过改进算法，使控制回路的周转时间缩短了约2倍。(3)研制了一种用于JNLT执行器的新型磁流体阻尼器系统。(4)精确测量和分析了夜间反射镜产生的微热对流。(5)稳像器，成功构建了测量大气湍流引起的恒星快速像移并通过伺服控制对其进行补偿的自适应光学系统。(6)研制并表征了构成自适应光学系统的超薄玻璃反射镜和压电致动器。

National Astronomical Observatory is planning to build an 8m telescope (Japan National Large Telescope : JNLT) for optical and infrared astronomy on top of Mauna Kea, Hawaii. A thin meniscus primary mirror with an active optics system will be used for JNLT to achieve the best imaging quality at a reasonable cost. Another important innovation to be used for improving the imaging quality of JNLT is the adaptive optics system. The wavefront aberration due to the atmospheric turbulence is measured and quickly compensated for by rapid adaptive optical components.The achievements of the present research in these regards are as follows :(1) An automatic control system in a closed loop to operate the active optics of a 62cm engineering telescope was established.(2) The turn around time of the control loop was shortened by a factor of about two by improving algorithms.(3) A new type damper system using magnetic fluid was developed for JNLT actuators.(4) Micro thermal convection arising from the mirror during night time was precisely measured and analyzed.(5) An image stabilizer, which measures the rapid image motion of a star due to the atmospheric turbulence and compensates for this motion by a servo control, was successfully constructed.(6) Very thin glass mirrors and piezo-electric actuators to constitute an adaptive optics system were developed and characterized.