High-speed multichannel length measurement with a CCD scanning line

This paper presents a CCD line scanning method, which allows the parallel measurement of up to six length measurement channels with a scanning rate of higher than 1000 Hz per channel. Mathematical methods - interpolation between the measured points - allow the combination of the results to find approximately the curvature of a moving surface or the misalignment of the sensor respectively. The sensor could be fitted in a compact case and works in a measurement range of 15 mm with a resolution better than 10 mu m. A subpixel resolution of 1 mu m can be achieved by computation. The requirements to high-speed operating sensors with high accuracy for length measurement are rising constantly. The instrumentation may readily be integrated into the production process (in-process measurement), e.g. for the ends of quality assurance and to make an automatic compensation of deviations possible. A very important fact is that the advantage of contactless measurement is avoiding the wear and tear of the probe tip, the material, respectively, on the other hand it reduces the error of measurement results from a thin film of cooling oil and chips. High pressure jets make sure that the workpiece surface in the measurement areas are blown free. Variations of the ambient temperature doesn't effect the results since the instrumentation is in a housing at stable temperature. Inductive and capacitive measurement methods have problems with curved surfaces. These methods are only used with expanded methods of mathematical compensation on these circumstances. Therefore the optical sensors are very interesting for achieving the requirements of the in-process measurements.