Zonal Bimorph Deformable Mirror Feasibility Study

大气层处于不断变化的状态。不同的气泡有不同的温度和密度，这会以不同的方式影响通过它的光。这种“湍流”限制了你能很好地看到远处的物体，并有效地限制了地面望远镜所能达到的分辨率。然而，由于自适应光学的出现，地面望远镜的大小已经逐渐增加；这可以用来校正湍流造成的模糊。现在有许多直径为8-10米的超大型望远镜(VLT)已经投入使用，配备了自适应光学系统。基于这些系统的成功，一个更大的直径为30米的极大望远镜(ELT)现在正被以欧洲南方天文台(ESO)为首的一个欧洲联盟考虑。带状双晶片可变形镜(ZBDM)是BAE系统先进技术中心五年投资的一项重要的新AO技术。ZBDM利用了通常与双压片镜相关的好处：结构简单、制造成本低、固有的坚固性，但同时，它们有可能扩大到具有数千个元件的大孔径。此外，低元件电容(通常比等效的叠层致动器DM小两个数量级)将使反射镜的驱动器更易于实现，散热更少。这项提议的主要目标是开展一项降低风险的研究，为将包括在计划中的E-ELT设施中的天文仪器(例如，用于多共轭自适应光学和用于行星探测仪器)的中等尺寸(间距2-5毫米，口径200-400毫米)可变形反射镜进行这项技术的开发。ZBDM技术可以灵活地履行多个AO角色。一个特别的领域是为高密度(2-5 mm)DM可用的最大行程限制提供解决方案。例如，基于堆叠式致动器技术的2 mm节距反射镜通常提供2um的最大行程。轻薄的ZBDM结构应能集成高音扬声器和低音扬声器，以实现双级、高PV冲程的“行星探测器”级器件。使用内部资金制造的单层61元件测试镜最近展示了+/-1.4um的致动器间行程，以及5 kHz的最低器件共振和+/-8um的PV行程。分析模型表明，高音单元间距为2 mm的双级ZBDM可以提供+/-5um的最大行程。这项提案包括一项为期两年的减少风险方案，将通过竞标七号方案来利用这一方案，以使技术向全面原型发展。第一阶段的主要目标是进行一系列降低风险的演习，以提高技术的成熟度，并制造一个小型演示器，为全面原型阶段提供坚实的基础。O器件模型将用于确定最大峰谷(PV)行程和带宽之间的特性权衡、可实现的影响函数的范围以及双级镜各层之间的相互依赖。O将进行组装和抛光试验，以确定减少/消除印刷风险和最大限度提高镜面平坦度的最佳方法。O目前的设计是基于标准的“软”PZT，它表现出滞后；已经确定了一些减少这种影响的策略。将对这些技术进行评估，最有希望的技术将用于小规模演示器。虽然ZBDM技术也可以应用于更大类型的镜子，但ELT大型AO镜子计划直接解决了这些应用问题。

The atmosphere is in a constant state of flux. Different pockets of air have different temperatures and densities which affect the light passing through it in different ways. This 'turbulence' limits how well you can see distant objects, and effectively puts a limit on the resolution that can be achieved with ground based telescopes. However, at the size of ground-based telescopes has gradually been increasing due to the advent of adaptive optics; this can be used to correct for the blurring caused by turbulence. There are now a number of Very Large Telescopes (VLTs), with 8-10 meter diameters that have been commissioned with adaptive optics. Based on the success of these systems, a much larger facility, the Extremely Large Telescope, (ELT), with a diameter of 30 meters is now being considered by a European Consortium lead by the European Southern Observatory (ESO) The Zonal Bimorph Deformable Mirror (ZBDM) is an important new AO technology that has resulted from five years of investment at BAE SYSTEMS Advanced Technology Centre. ZBDMs exploit the benefits normally associated with bimorph mirrors; simple construction, cost effective manufacture, and inherent ruggedness, but at the same time, they have the potential to be scaled up to large apertures with many thousands of elements. In addition, the low element capacitance (typically two orders of magnitude less than that of an equivalent stacked actuator DM), will make the driver for the mirror significantly easier to implement with much less heat dissipation. The main objective of this proposal is to carry out a risk reduction study on the development of this technology for medium (2-5mm pitch, 200-400mm aperture) sized deformable mirrors for the Astronomical Instrumentation which is to be included in the planned E-ELT facility (e.g. for multi-conjugate adaptive optics and for the planet-finder instrument). ZBDM technology has the flexibility to fulfil a number of AO roles. One particular area is to offer a solution to the limitations in the maximum stroke available with high density (2-5mm) DM's. For example, 2mm pitch mirrors based on stacked actuator technology typically provide a maximum stroke of 2um. The thin, lightweight ZBDM structure should enable the integration of both 'tweeter' and 'woofer' DMs to realise a dual-stage, high PV stroke 'planet-finder' class device. A single layer, 61 element test mirror fabricated using internal funds has recently demonstrated an inter-actuator stroke of +/-1.4um, coupled with a lowest device resonance of 5 kHz and a PV stroke of +/-8um. Analytical modeling suggests that a dual stage ZBDM with a tweeter pitch of 2mm could deliver a maximum stroke of +/-5um. This proposal covers a two year risk reduction programme that would be exploited through a bid into the FP7 programme to progress the technology towards a full scale prototype. The main objective of this first stage is to undertake a series of risk reduction exercises which will increase the maturity of the technology, and to fabricate a small scale demonstrator which will provide a firm basis for the full scale prototype phase. o Device models will be used to determine the characteristic trade-off between maximum peak-valley (PV) stroke and bandwidth, the range of influence functions that can be achieved, and the inter-dependence of layers for a dual stage mirror. o Assembly and polishing trials will be undertaken in order to determine the best way to reduce / eliminate the risk of print through and maximize mirror flatness. o The current design is based on standard 'soft' PZT, which exhibits hysteresis; a number of strategies for reducing this effect have already been identified. These will be assessed, and most promising technique will be used in the small scale demonstrator. While ZBDM technology can also be applied to larger mirror types, these applications are being addressed directly by the ELT Large AO Mirror Programme.