Laser Interference Sensor for 4D Shape and Vibration Measurement with Camera Based Uncertainty Reduction

Absolute shape and vibration measurements of rotating workpieces and cutting tools in CNC machines are significant for machine operation optimizations and thereby for improving the machining accuracy. Simultaneous position and velocity measurements enable absolute 3D shape measurements of fast rotating workpieces for instance for monitoring the cutting process in a lathe. Laser Doppler distance sensors (PLDDS) enable simultaneous position and velocity measurements with a single sensor head by evaluating the scattered light signals. However, superposed speckle signals, temperature drifts or mechanical scanning result in an increased velocity, distance and shape uncertainty.
To overcome above drawbacks, in this dissertation a novel camera based PLDDS is realized. It can separate the speckle signals for the Doppler frequency and distance evaluations to reduce the speckle noise. A fringe spacing calibration method that can be conducted in-situ is realized to eliminate the fringe spacing uncertainty resulting from temperature drifts. Coherent fiber bundles were employed for the first time to forward the scattered light towards the cameras. This removes the cameras from the sensor head and therefore enables a compact and passive sensor head with keyhole access. Furthermore, the flexible applications of 4D shape measurement without sensor scanning and bi-directional tool tip vibration measurements with only one sensor head were achieved which can be used for the machine operation optimization in the industry.