Patent ID: 7068378

Claim:
A measuring apparatus used for a grinding tool using a grinding surface comprising a surface of a tool base on which a large number of abrasive grains are discretely formed, to measure the amount of projection of each of the abrasive grains, the apparatus comprising: a camera unit provided opposite the grinding surface to pick up an image of the grinding surface; and a control unit connected to the camera unit, the control unit comprising: means for moving a focal position of the camera unit in a direction perpendicular to the grinding surface; means for causing the camera unit to pick up the image of the grinding surface synchronized with movement of the focal position; means for storing a first basic image pattern corresponding to an image obtained when the focal position is set at the tip of the abrasive grain, a second basic pattern corresponding to an image obtained when the focal position is set at the bottom of the abrasive grain, and a third basic image pattern obtained when the focal position is set at the tip and bottom of the abrasive grain; means for comparing the image data, every time the data is obtained, with the first, second and third basic image patterns means for detecting image data approximate to the first, second, and third image patterns on the basis of a result of the comparison; and means for calculating the amount of projection of the abrasive grains on the basis of the focal position at which the detected image data was obtained by the camera unit.