DEVICE FOR ACCURATELY MEASURING DIMENSION

PURPOSE:To perform non-contact continuous efficient measurement without stopping a polishing machine, by finding out the change in the distance between a distance detector on a correction ring and the top of a weight on a fixation plate holding a workpiece secured on the bottom of the plate. during polishing work. CONSTITUTION:A workpiece 2 is bonded to the bottom of a fixation plate 3 located over a surface plate 1 made of a hard cloth, ceramic or the like. A weight 4 is placed on the top of the fixation plate 3. A ring 5 for correcting the flatness of the surface plate 1 is placed with a prescribed gap to the peripheral surface of the fixation plate 3. An eddy current detector 8 is secured by a support 6 on the ring 5. As the thickness of the workpiece 2 decreases due to the polishing of the workpiece by rotating the fixation plate 3, the distance between the tip of the detector 8 and the top of the weight 4 increases so that the voltage of the detector changes. The voltage is applied to a calculator 9. When the polished quantity has reached a target, a signal is entered into a controller 10 to stop driving.