NONCONTACT MEASURING INSTRUMENT FOR INSIDE AND OUTSIDE DIAMETERS

PURPOSE:To measure the inside diameter or the outside diameter with a high accuracy in accordance with the extent of movement of an optical system for focusing by continuously rotating a work and observing the change of a surface to be measured due to this rotation in the in-focus state by the optical system. CONSTITUTION:A work 3 is fixed on a turntable 4, and an optical system 5 is held on a feed unit 6 and is driven in X-axis, Y-axis, and Z-axis directions by a control unit 8. An objective lens 11 of the optical system 5 has a high power of about 100 magnifications, and an industrial camera 13 is connected above an eyepiece lens 12. In this constitution, the work 3 is rotated and the optical system 5 is moved forward and backward to obtain the in-focus state of the inside surface. The in-focus state is determined in accordance with the image forming state of the industrial camera 13 by the automatic focusing method. An angle theta of turning of the work 3 and a reference distance D between the optical axis of the optical system 5 and the center of turning of the turntable 4 are inputted to an image unit 14 to calculate the inside diameter.