New three-dimensional fiber probe for multisensor coordinate measurement

Increasing manufacturing accuracy requirements enforce the development of innovative and highly sensitive measuring tools. Especially for measurement with submicrometer accuracy, the sensor principle has to be chosen appropriately for each measurement surface. Modern multisensor coordinate measurement systems allow automatic selection of different sensor heads to measure different areas or properties of a sample. As an example, different types of optical sensors as well as tactile sensors can be used within the same measuring system. I describe different principles of optical sensors used in multisensor coordinate measurement systems as well as a new approach for tactile measurement with submicrometer accuracy. A special fiber probe has been developed. The tip of the fiber probe is formed as a sphere. The lateral position of this sphere is observed by a microscope objective and can be determined within a fraction of a micrometer. Additionally, a novel optical setup now allows the determination of the z-position of the fiber tip with submicrometer accuracy. For this purpose, an interferometer setup is used. The laser light is coupled into the optical fiber. The light exiting the fiber tip is collected by the microscope objective and superposed with a reference wave, generated directly from the laser. The result is an interference signal that is recorded by the camera and processed by a computer. With this setup, the z-displacement of the fiber sphere can be measured with an accuracy of a fraction of the laser wavelength used. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.OE.51.8.081502]