Shape measurement by means of imaging using partially coherent illumination - part 2 (Spice II)

光学计量是许多生产过程中保证质量的重要前提。在微元器件的大规模生产中，需要一种测量速度快、测量不确定度低、景深大、对振动不敏感的测量技术。然而，根据当前技术状态，结合这些特性的测量系统是不可用的。为此，在第一个供资阶段审查了利用部分空间相干光进行光学成像进行形状测量的局限性和可能性。开发的方法可以快速、人眼安全和振动不敏感的形状测量扩大景深的微型零件。然而，该方法对粗糙表面物体的测量不确定度目前仍在几微米范围内。然而，测量不确定度的降低是工业应用的决定性因素。因此，所请求的延续项目的目标是实现一种具有上述属性的测量方法，用于测量测量不确定度等于或小于1微米的技术部件的形状。为了实现这一目标，应使用多个LED作为光源从不同方向顺序或同时照射测量对象。采用基于像素的主成分分析方法对相应的记录进行评估，在延拓工程的第一阶段，通过使用可通过电势调节焦距的透镜(可调谐透镜)来实现小于1秒的测量时间；在延拓工程的第二阶段，使用开关速度几乎是可调透镜的10倍的数字微镜阵列(DMD)来显著提高测量速度。为了在深度扫描过程中实现快速数据采集，需要补偿由于用作照明源的LED的波长光谱而引起的DMD的角色散。在申请的延续项目结束时，应提供用于上述应用的快速、坚固的测量系统的演示，测量不确定度为1微米或更小。

Optical metrology is an important prerequisite for quality assurance in many production processes. For applications in the mass production of micro-components, a measurement technology is required that has a high measurement speed, low measurement uncertainty, an extended depth of field and is insensitive to vibrations. However, a measuring system that combines these properties is not available according to the current state of the art. For this reason, the limits and possibilities of shape measurement by means of optical imaging using spatially partially coherent light were examined in the first funding phase. The developed method enables fast, eye-safe and vibration-insensitive form measurement of micro parts with an extended depth of field. However, the measurement uncertainty of the method for objects with a rough surface is currently still in the range of a few micrometers. The reduction of the measurement uncertainty is, however, a decisive factor for an industrial application.The aim of the requested continuation project is therefore to implement a measurement method with the above-mentioned properties for measuring the shape of technical components with a measurement uncertainty of equal or less than 1 µm. To achieve this goal, the measurement object shall be illuminated sequentially or simultaneously from different directions using several LEDs as light sources. The corresponding recordings are evaluated using a pixel-based approach by principal component analysis.In the first phase of this continuation project, a measuring time of less than one second is to be achieved by using a lens (tunable lens) that can be adjusted in the focal length by means of an electrical potential.In the second phase of this continuation project, the measurement speed is then to be increased significantly by using a digital micromirror array (DMD) with a switching speed that is almost 10 times higher than that of an adjustable lens. To do this, it is necessary to compensate for the angular dispersion of the DMD due to the wavelength spectrum of the LEDs used as the source of illumination, in order to enable fast data acquisition within the depth scanning process.At the end of the continuation project applied for, a demonstrator of a fast, robust measurement system for the application described above with a measurement uncertainty of 1 µm or less should be available.