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.

第一个项目阶段的目的是开发用于传输中透明对象的几何测量的偏差测量系统。与已建立的测量技术相比，这种类型的测量策略具有显着优势，这些技术在反射中分别测量了这种标本的前表面和后表面。两种表面的几何关系和折射的效果本质上包含在测量数据中，因此可以简单地重建完整的几何形状和折射索引。在第一个项目阶段A偏差测量系统（以精度和分辨率为精度）进行了优化。该设置已使用高端放射线刻度显示器，而不是广泛使用的消费级计算机监视器。对于测量系统，已经实施了不同种类的重建算法。对入射射线和折射射线之间的对应关系的偶数评估尚未产生令人满意的结果，因为测得的表面的偏离可以达到1毫米。但是，通过基于Zernike多项式的样品模型，可以实现全局重建算法，并同时测量针对界面性透明镜头空白的几何形状和折射索引。形式定义的参数的偏离小于2％，对应于先前发现的30 µm的最大表面表面的最大偏差，必须将该技术进一步开发的潜力被评为高。但是，在当前状态下，与已建立的测量系统相比，系统的规格没有竞争力。特别是系统的出发和测量时间是高度的数量级。因此，该项目延续的目的是通过增强算法和新颖的测量策略的结合来显着改善规格。除了分析和最小化全球重建中的系统离发外，还必须进一步开发重建的重建，因为它在测量技术的灵活性方面具有相当大的潜力。可以预料的是，特别是直接测量折射的几何形状和索引的可能性会打开各种应用。一旦规范得到显着改进，复杂形成的透明物体的自动测试将是可行的。