MEASURING APPARATUS OF ROTATING AMOUNT

摘要

PURPOSE:To detect the rotating amount of a rotary shaft of a small radius at low costs and considerably accurately by detecting the movement of a silhouette pattern generated when a lattice pattern is illuminated by a light source consequent upon the rotation of the rotary shaft. CONSTITUTION:This measuring apparatus has a scale 2, a light source 1 and an optical sensor 5. The scale 2 is cylindrical or conical, having the diameter larger than that of a rotary shaft 4a. A lattice pattern 3 is formed in the peripheral surface of the scale 2. Moreover, the scale 2 is coaxially mounted with the rotary shaft 4a. The light source 1 projects light to the lattice pattern 3 of the scale 2 so as to generate a silhouette pattern. The optical sensor 5 as a photodetecting means detects the movement of the silhouette pattern generated when the lattice pattern 3 is illuminated by the light source 1 as the rotary shaft 4a is rotated. Since the lattice pattern 3 for generating a silhouette pattern is formed in the peripheral surface of the scale 2 of the larger diameter than that of the rotary shaft the rotating amount of which is to be measured, the lattice pattern can be formed easily and positively with fine pitches.