Institute of Scientific Instruments, Academy of Sciences of the Czech Republic, Královopolská 147, Brno 612 64, Czech Republic.
Sensors (Basel). 2011;11(8):7644-55. doi: 10.3390/s110807644. Epub 2011 Aug 2.
The influence of the refractive index of air has proven to be a major problem on the road to improvement of the uncertainty in interferometric displacement measurements. We propose an approach with two counter-measuring interferometers acting as a combination of tracking refractometer and a displacement interferometer referencing the wavelength of the laser source to a mechanical standard made of a material with ultra-low thermal expansion. This technique combines length measurement within a specified range with measurement of the refractive index fluctuations in one axis. Errors caused by different position of the interferometer laser beam and air sensors are thus eliminated. The method has been experimentally tested in comparison with the indirect measurement of the refractive index of air in a thermal controlled environment. Over a 1 K temperature range an agreement on the level of 5 × 10(-8) has been achieved.
空气折射率的影响已被证明是提高干涉位移测量不确定度的主要问题。我们提出了一种方法，使用两个反向测量干涉仪作为跟踪折射仪和位移干涉仪的组合，参考激光源的波长与由具有超低热膨胀系数的材料制成的机械标准。该技术将指定范围内的长度测量与一个轴上的折射率波动测量相结合。因此，消除了由于干涉仪激光束和空气传感器不同位置引起的误差。该方法已通过实验与在热控环境中对空气折射率的间接测量进行了比较。在 1 K 的温度范围内，达到了 5×10(-8)的水平。
