Novel three dimensional shape measurement technique for fast rotating objects

以亚微米精度测量快速旋转的零件的形状和位置使加工技术取得了重要的进步。在第一个资助阶段，系统地研究了一种新型的激光多普勒测距传感器(P-LDD传感器)。P-LDD传感器系统采用同时测量横向表面速度和轴向表面距离的方法，通过小孔通道测量旋转轴的绝对形状和位置。实现了一项科学突破。通过观察不同角度下的散射光，并采用新颖的信号评定方法，使测量不确定度降低了一个数量级以上。此外，P-LDD传感器系统被集成到车床中(与布伦瑞格的PTB合作)，并在高横向表面速度下以300 nm的标准偏差测量了工件的形状。然而，这种新系统的总测量不确定度目前受到散斑噪声和校准函数的热漂移的限制。此外，横向分辨率限制了传感器在宏观几何特征测量中的应用。因此，拟议的第二个资助期的目的是减少由于斑点效应和校准函数漂移(系统不确定性)引起的测量不确定性，并提高横向分辨率。这将使旋转物体具有亚微米不确定度的宏观和微观几何形状测量成为可能。为此，将在系统中引入摄像机而不是单一的探测器，并将对运动散斑图像进行新的图像处理和基础研究。图像处理将能够对单个斑点进行评估。因此，当前在探测器信号中出现的相位跳变将被消除。初步的数值实验表明，散斑引起的测量偏差有所减小。使用矩阵摄像机和扩展的图像处理可以实现额外的现场校准，这将被应用和表征，以减少系统偏差。此外，通过相机扩展P-LDD传感器系统可以提高横向分辨率。因此，可以将自由曲面零件的微观几何特征附加到形状中进行原位解析。

The measurement of shape und position of fast rotating workpieces with sub-micron precision enables important advances in process technology. During the first funding period a novel laser Doppler distance sensor (P-LDD Sensor) was investigated systemically. The P-LDD sensor system employs the simultaneous measurement of the lateral surface velocity and the axial surface distance, in order to measure the absolute shape and position of rotation axis with keyhole access. A scientific breakthrough was accomplished. The measurement uncertainty has been reduced by more than one magnitude by observing the scattered light under different angles and employing novel signal evaluation. Furthermore, the P-LDD sensor system was integrated into a lathe (cooperation with PTB in Braunschweig) and the shape of a workpiece was measured with a standard deviation of 300 nm also at high lateral surface velocities. However, the total measurement uncertainty for this novel system is currently limited by speckle noise and thermal drifts of the calibration functions. Additionally, the lateral resolution is limiting the application of the sensor to measurements of macro geometric features.Therefore, the aim of the proposed second funding period is to reduce the measurement uncertainty due to the speckle effect and due to drifts of the calibration functions (systematic uncertainties) as well as to increase the lateral resolution. This will enable macro- and micro-geometric shape measurements with sub-micron uncertainty at rotating objects. For this purpose cameras will be introduced to the system instead of single detectors and novel image processing for moving speckle pattern will be applied and fundamentally investigated. The image processing will enable an evaluation of single speckles. Therefore phase jumps, which currently occur in the detector signal will be eliminated. Preliminary, numerical experiments show a reduction of the speckle induced measurement deviations. Using a matrix camera and an extended image processing enables an in-situ calibration additionally, which will be applied and characterized to reduce systematic deviations. Furthermore, the extension of the P-LDD sensor system by a camera enables an increased lateral resolution. Thus, micro-geometric features of free form parts can be resolved additionally to the shape in-situ.