Proposal of concurrent measurement method for spindle radial, axial and angular motions using concentric grating interferometers

In this paper, we propose a measurement method for spindle radial, axial and angular motions using concentric circle grating interferometers. In this method, the grating is installed on top of the spindle. Three optical sensors, which consist of two interferometers, are fixed over the grating. One interferometer detects an interference signal between reflection lights from a fixed mirror and the grating for vertical displacement measurement. The other interferometer detects an interference signal between ±first diffraction lights from the grating for lateral displacement measurement. Using three optical sensors, radial, axial and angular motions of the spindle, can be measured concurrently.