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，可以非常精确地确定反射表面的细节。它定量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）的变形。从畸变测量得到的测量量是物体表面的每个点的斜率。通过对数据进行微分，可以获得局部表面曲率，并且该方法对于局部干扰的非常高的灵敏度导致高度分辨率为1纳米，而不需要付出很大的努力。因此，该方法已进入工业质量检测领域。整合坡度数据以确定绝对物体形状是迄今为止最困难的任务。虽然已经成功地模拟和测试了用于校准相机和系统几何形状的各种方法，但是关于真实的显示器赋予在所有迄今存在的分析中被假定为理想的参考图案的偏差知之甚少。大型显示器不能再被视为平面，并且位于发光像素前面的散射屏的影响和观察角度对强度的影响迄今为止都没有被系统地研究。所提出的项目的目标是研究显示器的适当表征，包括摄像机和测量系统校准，以降低基于偏折法的测量系统的测量不确定性，该测量系统使用监视器，目前在平坦或浅曲面上的测量不确定性约为4至15 µm甚至对于更强的弯曲表面，也可以减小约一个数量级至小于0.5 µm。在该项目中，必须实现以下子目标：i）显示器的特性和描述真实的显示器行为的模型的开发。ii）将显示模型集成到相机的视觉射线校准中。iii）新颖的系统校准，包括用于测量稳定和非稳定表面的程序的显示模型和视觉射线校准。iv）基于经验的结果，通过使用平坦和弯曲的测试样品的鉴定测量，系统地描述测量程序的偏差。（v）通过比较不考虑和考虑真实的显示器的特性以及改进的系统校准的测量结果，实验证明测量不确定性降低。在该项目的第一部分，IPROM调查的行为的影响，真实的显示器，而BIAS制定和实验验证扩展的方法，系统校准的测量系统的基础上偏转。在项目接近尾声时，将建立一个联合测量系统。

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.