Highly accurate deflectometric shape measurement including the non ideal properties of a display as reference plane

相位测量偏转法是一种高灵敏度的二维光学测量方法，可以非常准确地确定反射表面的细节。它定量地测量被测量表面反射的参考结构（通常由计算机显示器表示）的畸变。畸变测量得到的测量量是物体表面各点的斜率。通过对数据进行微分，可以获得局部表面曲率，并且该方法对局部扰动具有很高的灵敏度，因此可以毫不费力地获得一纳米量级的高度分辨率。因此，这种方法在工业质量检测中得到了应用。整合坡度数据来确定物体的绝对形状是迄今为止比较困难的任务。虽然各种校准相机和系统几何形状的方法已经成功地建模和测试，但对于在所有迄今为止存在的分析中假设是理想的参考模式的真实显示所带来的偏差知之甚少。大型显示器不能再被看作是平面，目前还没有系统地研究过位于发光像素前的散射屏的影响以及观测角度对亮度的影响。拟议项目的目标是对显示器进行充分的表征研究，包括相机和测量系统校准，以减少基于偏转测量的测量系统的测量不确定度，使用监视器从目前在平坦或浅曲面上的约4至15 μ m减少约一个数量级到小于0.5 μ m，即使对于更强的曲面。在该项目中，必须实现以下子目标：i)显示器的表征和描述真实显示器行为的模型的开发。ii)将显示模型集成到摄像机视觉光线标定中。iii)新颖的系统校准，包括显示模型和用于测量稳态和非稳态表面的视觉射线校准。iv)基于经验的结果，通过使用平面和弯曲测试样品的鉴定测量，系统地描述测量过程的偏差。v)降低测量不确定度的实验证据，比较没有和考虑真实显示器的特性和改进的系统校准的结果。该项目是由两位申请人合作设计的。在项目的第一部分，IPROM研究了真实显示器行为的影响，而BIAS则制定并实验验证了基于偏转计的测量系统的系统校准扩展方法。在项目结束时，将实现一个联合测量系统。

Phase-measuring deflectometry is a highly sensitive, 2-D optical measurement method that can determine details of reflective surfaces very accurately. It measures quantitatively the distortion of a reference structure (often represented by a computer monitor) that is reflected by the surface to be measured. The measured quantity resulting from the distortion measurement is the slope for each point of the object surface. By differentiating the data, the local surface curvature can be obtained, and the very high sensitivity of the method with regard to local disturbances leads to a height resolution on the order of one nanometre with little effort. Therefore, this method has found its way into industrial quality inspection. Integration of the slope data to determine the absolute object form is by far the harder task. While various methods for calibration of the camera and the system geometry have been modelled and tested successfully, very little is known about the deviations that a real display imparts to a reference pattern assumed to be ideal in all hitherto existing analyses. Large displays can no longer be regarded as planar surfaces, and neither the impact of the scattering screen located in front of the luminescent pixels nor the influence of the observation angle on the intensity have hitherto been systematically investigated.The goal of the proposed project is to do research on an adequate characterization of the display, including the camera and measurement system calibration in order to reduce the measurement uncertainty of measurement systems based on deflectometry using a monitor from currently around 4 to 15 µm at flat or shallow curved surfaces by around one order of magnitude to smaller than 0,5 µm even for stronger curved surfaces. Within the project, the following sub-goals have to be achieved: i) Characterization of displays and development of a model describing the behavior of real displays. ii) Integration of the display model in the vision ray calibration of the camera. iii) Novel system calibration including the display model and the vision ray calibration for procedures for the measurement of steady and unsteady surfaces. iv) Empirically based results to systematically describe deviations of the measurement procedure via qualification measurements using flat and curved test samples. v) Experimental evidence of reduced measurement uncertainty comparing results without and with consideration of the properties of real displays and improved system calibration.The project is designed as a cooperation of two applicants. During the first part of the project, IPROM investigates the influence of the behavior of real displays, while BIAS formulates and experimentally verifies extended approaches of system calibration for measurement systems based on deflectometry. Towards the end of the project, a joint measurement system will be realized.