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Three-dimensional shape measurement of transparent objects by pattern transmission photogrammetry

图案透射摄影测量透明物体三维形状测量

基本信息

批准号：
106026994
负责人：
Dr.-Ing. Marcus Petz
金额：
--
依托单位：
Institut für Produktionsmesstechnik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2008
资助国家：
德国
起止时间：
2007-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/106026994?language=en
关键词：
Three dimensional shape measurement transparent

项目摘要

The objective of the first project phase has been the development of a deflectometric measurement system for the geometric measurement of transparent objects in transmission. This type of measurement strategy offers significant advantages compared to established measurement techniques which separately measure the front and rear surface of such a specimen in reflection. The geometric relation of both surfaces and the effect of refraction are intrinsically contained in the measurement data so that it is possible to reconstruct the complete geometry and the index of refraction simultaneously.During the first project phase a deflectometric measurement system, optimized for accuracy and resolution, has been set up. Instead of widely-used consumer-grade computer monitors, high-end radiologic grayscale displays have been used for this setup. For the measurement system different kinds of reconstruction algorithms have been implemented. A pointwise evaluation of correspondences between incident and refracted rays did not yet yield satisfying results because the deviations of the measured surface can become up to 1 mm. However, with a model of the specimen based on Zernike-polynomials it has been possible to implement a global reconstruction algorithm and to simultaneously measure the geometry and the index of refraction for an aspheric ophthalmic lens blank. The deviation of the form-defining parameters was less than 2%, corresponding to a maximum deviation of the measured surface of 30 µm.Based on the previous findings the potential for further development of the technique must be rated as high. In the current state, however, the specifications of the system are not competitive compared to established measuring systems. In particular the systematic deviations and the measurement time are an order of magnitude to high. The objective of the proposed continuation of the project therefore is a significant improvement of the specifications by means of a combination of enhanced algorithms and novel measurement strategies. Besides an analysis and minimization of systematic deviations in the global reconstruction, specifically the pointwise reconstruction has to be developed further, because it features a considerable potential with respect to the flexibility of the measuring technique. It is to be expected, that especially the possibility of a direct measurement of both geometry and index of refraction opens various applications. An automated 100%-testing of complex formed transparent objects would be feasible as soon as the specifications have been significantly improved.

项目第一阶段的目标是开发一个偏折测量系统，用于透射透明物体的几何测量。这种类型的测量策略提供了显着的优势相比，已建立的测量技术，分别测量的正面和背面的反射这样的标本。两个表面的几何关系和折射效应都包含在测量数据中，因此可以同时重建完整的几何形状和折射率。在第一个项目阶段，建立了一个偏转测量系统，优化了精度和分辨率。取代广泛使用的消费级计算机显示器，高端放射学灰度显示器已用于此设置。对于测量系统，已经实现了不同种类的重建算法。入射和折射光线之间的对应关系的逐点评估还没有产生令人满意的结果，因为测量表面的偏差可以达到1 mm。然而，与基于泽尼克多项式的样本模型，它已经可以实现一个全局重建算法，并同时测量几何形状和折射率的非球面眼科透镜空白。形状定义参数的偏差小于2%，对应于30 µm的测量表面的最大偏差。根据先前的发现，该技术的进一步发展潜力必须被评为高。然而，在目前的状态下，该系统的规格与已建立的测量系统相比没有竞争力。特别地，系统偏差和测量时间是高的数量级。因此，该项目拟议继续的目标是通过结合增强的算法和新的测量策略来显著改进规范。除了分析和最小化全局重建中的系统偏差外，还必须进一步开发逐点重建，因为它具有相当大的潜力，具有测量技术的灵活性。可以预期的是，特别是直接测量几何形状和折射率的可能性开辟了各种应用。一旦规格得到显著改进，复杂成型透明物体的自动化100%测试将是可行的。