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Frequency Scanning Interferometry for Laser Trackers and Laser Tracers

用于激光跟踪仪和激光追踪仪的频率扫描干涉测量

基本信息

批准号：
EP/H018220/1
负责人：
Armin Reichold
金额：
$ 62.5万
依托单位：
University of Oxford
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FH018220%2F1
关键词：
Frequency Scanning Interferometry Laser Trackers

项目摘要

With the introduction of computer numeric control (CNC) to manufacturing machines such as lathes, mills or the more exotic wire-erosion machines we have seen a dramatic increase in our ability to produce increasingly large components with ever improving accuracy. Inspired by this technological advance engineers are designing more products to take advantage of this ability, increasing the demands on accuracy even further. Largely driven by this virtuous circle is the field of co-ordinate metrology. Here both manufacturing machines and the products they produce are being checked against the stringent dimensional tolerances of modern engineering.As the number and the accuracy of CNC machines improves so must the techniques used in metrology. In fact, the accuracy used by metrologists must always be a step ahead of manufacturing to be able to calibrate manufacturing machines. Lasers have revolutionised the area of co-ordinate metrology. Because laser can emit light with highly stable wavelength the offer unprecedented accuracy in measuring distance differences or changes through fixed frequency, differential interferometry. Instruments such as laser trackers which have rapidly become the dominant instruments in large scale, high accuracy metrology utilise this ability and combine it with angle measurements to determine three dimensional displacements. The angle measurements normally limit the accuracy of laser trackers. Laser tracers, originally developed by NPL and aimed at even higher accuracies, operate without angle measurement. They only measure the distance to the target but do so from several positions allowing the displacements to be computed from the distance measurements alone by process called sequential multilateration. Laser tracers are close to the top of the food chain of metrology instrument. They are ultra high accuracy instruments that can be used to calibrate other metrology instruments, as well as CNC machines. One of the major drawbacks of differential interferometry is the need for the laser beam to continuously illuminate the same target. If the beam is broken, for example because the new target position is reached on a path which is partially obscured or because the tracker can not follow the target fast enough, the measurement needs to be restarted, requiring valuable operator time.In this project we seek to introduce the ability to measure absolute distances with accuracies comparable to those obtained from differential interferometry into laser tracers. We will try to integrate a technology called Frequency Scanning Interferometry (FSI), in a form developed in the John Adams Institute for Accelerator Science (JAI) at Oxford University into a laser tracer allowing it to robotically switch between targets and be tolerant to beam brakes.As an additional benefit, FSI is capable of measuring the distance to several targets at the same time if a wide laser beam is used to illuminate many targets at the same time. Exploiting this ability could lead to instruments that can not only measure the position of a target but also its orientation in space.Among all of these technological developments we will also critically look at ways of reducing the cost of FSI to make it more attractive for a wide range of applications in co-ordinate metrology.FSI works because modern lasers can not only have a single very well defined wavelength but they can - thanks to developments in the telecommunications industry - also continuously change this wavelength with time. So lasers are again set to improve co-ordinate metrology in a fundamental way.

随着计算机数字控制（CNC）在车床、米尔斯或更奇特的线切割机等制造机器中的引入，我们已经看到我们生产越来越大的部件的能力急剧增加，并且精度不断提高。受这一技术进步的启发，工程师们正在设计更多的产品来利用这一能力，进一步提高了对精度的要求。受这种良性循环驱动的主要是坐标计量领域。在这里，制造机器及其生产的产品都要根据现代工程的严格尺寸公差进行检查。随着数控机床数量和精度的提高，计量技术也必须提高。事实上，计量师使用的精度必须始终领先于制造业，以便能够校准制造机器。激光已经彻底改变了坐标计量领域。由于激光器可以发射具有高度稳定波长的光，因此通过固定频率、差分干涉测量法在测量距离差或变化方面提供了前所未有的精度。诸如激光跟踪仪之类的仪器已经迅速成为大规模、高精度计量中的主导仪器，它们利用这种能力并将其与角度测量结合联合收割机来确定三维位移。角度测量通常限制激光跟踪仪的精度。最初由NPL开发的激光跟踪仪旨在实现更高的精度，无需角度测量。它们只测量到目标的距离，但从几个位置这样做，允许通过称为顺序迭代的过程单独从距离测量计算位移。激光示踪仪是接近食物链顶端的计量仪器。它们是超高精度仪器，可用于校准其他计量仪器以及CNC机床。差分干涉测量法的主要缺点之一是需要激光束连续照射同一目标。如果光束被打断，例如因为新的目标位置到达了一条部分被遮挡的路径，或者因为跟踪器不能足够快地跟踪目标，测量需要重新开始，这需要宝贵的操作时间。在这个项目中，我们试图引入测量绝对距离的能力，其精度与从差分干涉测量到激光跟踪器中获得的精度相当。我们将尝试将一种名为频率扫描干涉测量（FSI）的技术，以牛津大学约翰亚当斯加速器科学研究所（JAI）开发的形式集成到激光示踪剂中，使其能够在目标之间自动切换并容忍光束制动。作为额外的好处，如果使用宽激光束同时照射多个目标，则FSI能够同时测量到多个目标的距离。利用这一能力可以使仪器不仅可以测量目标的位置，而且可以测量其在空间中的方向。在所有这些技术发展中，我们还将认真研究降低FSI成本的方法，使其在坐标计量的广泛应用中更具吸引力。FSI之所以有效，是因为现代激光器不仅可以具有单一的非常明确的波长，而且可以-由于电信行业的发展-也随着时间不断地改变这个波长。因此，激光器再次被设置为从根本上改善坐标计量。