Determination of the central position of a rotating object by laser Doppler velocimetry

Abstract

Determination of the central position of rotation is an important technique. This technique is, for example, useful for the operation of a machine tool. If the height of the tool is not adjusted to the central position of rotation, the central portion of a workplace is left without being cut. Here a new method of using laser Doppler velocimetry (LDV) is proposed for this determination. The principle is based on the fact that the tangential velocity of the rotating object is proportional to the distance between a measuring point and a central position. Therefore the tangential velocity is measured by the differential LDV with a microscope and the central position is determined by finding the place where the tangential velocity becomes zero. In the experiments, the velocities at two points to each axis of the Cartesian coordinate were measured, where the separation of two points is measured in advance. By the simple calculation with measured values, the central position where the tangential velocities become zero could be determined within the accuracy of 1–2 μm.