Rottenkolber M, Podbielska H
Institute of Physics, Technical University of Wroclaw, Poland.
Acta Ophthalmol Scand. 1996 Aug;74(4):348-53. doi: 10.1111/j.1600-0420.1996.tb00706.x.
We developed a method for measuring ophthalmic surfaces based on a Twyman-Green interferometer.
To demonstrate the accuracy, we measured the anterior surface of four used hard contact lenses and evaluated the interference pattern with phase shift technique. The obtained interferograms were evaluated by an image processing system.
The interferometric resolution of the measurement is up to lambda/20 (30 nm) which refers to a dioptric resolution of about delta D = 10(-3) m(-1) for typical anterior radii of curvature. The dioptric maps were calculated from the height distribution. As we used a focus tracking distance measurement setup with an accuracy of 10 microns we could determine the absolute value of the dioptric number to be delta D approximately 0.04 m-1. To demonstrate the accuracy we tested contact lenses which were specified to have a spherical anterior surface. Obviously, the topography of contact lenses changes when worn. We measured astigmatic deviations up to 0.6 D in the central zone of the lenses. We briefly discuss the possibilities of this method concerning a topographer for measuring the fine corneal surface structure.
The presented Twyman-Green interferometer with distance measurement and image processing system is a very accurate method for measuring the topographic properties of ophthalmic surfaces. The method may also be useful for studying the distribution of the tear layer on the contact lens, or the corneal topography.
我们开发了一种基于泰曼-格林干涉仪测量眼表的方法。
为证明其准确性，我们测量了四副用过的硬性隐形眼镜的前表面，并采用相移技术评估干涉图样。通过图像处理系统对所得干涉图进行评估。
测量的干涉分辨率高达λ/20（30纳米），对于典型的前曲率半径，这对应约δD = 10^(-3) m^(-1) 的屈光度分辨率。从高度分布计算出屈光度图。由于我们使用了精度为10微米的焦点跟踪距离测量装置，我们能够确定屈光度值的绝对值约为δD 0.04 m^(-1)。为证明准确性，我们测试了标称具有球面形前表面的隐形眼镜。显然，隐形眼镜佩戴后其形貌会发生变化。我们在镜片中心区域测量到高达0.6 D的散光偏差。我们简要讨论了该方法用于测量精细角膜表面结构的地形图仪的可能性。
所介绍的带有距离测量和图像处理系统的泰曼-格林干涉仪是一种测量眼表形貌特性的非常精确的方法。该方法对于研究隐形眼镜上泪液层的分布或角膜地形图也可能有用。
