METHOD AND DEVICE FOR MEASURING DIMENSION

摘要

PURPOSE:To improve the measurement precision by arranging a measuring member so that it faces a face to be measured of a cylindrical object with a proper gap between them and scanning this gap with a spot light and detecting a prescribed higher harmonic component of the optical signal transmitted through the gap. CONSTITUTION:A cylindrical object 1 to be measured is placed on an attaching base 2, and a measuring member 4 having a knife edge 3 faces the object 1 from above with a proper gap between them. The laser light emitted from a gas laser 8 as a light source scans the gap as a scanning beam through an oscillating mirror 12. The light transmitted through the gap is made incident to a photoelectric multiplier 7 through a light receiving optical system 6 and is converted to an electrical signal. This electrical signal is amplified in a preamplifier 18 and is inputted to a lock-in amplifier 19. The amplifier 19 detects and outputs a prescribed higher harmonic component out of Fourier series components of the electric signal. This output signal corresponds to the width of the gap, and dimensions of the outside diameter of the object 1 to be measured are calculated on a basis of this value.