| 摘要 |
PURPOSE:To carry out accurate V-block machining of a spectacle lens by obtaining the moving distance of a cutting point from a distance between the lens center of a pattern and the center of curvature of a copying board and from the angle of a contact point between said pattern and said copying board to a line connecting both the centers. CONSTITUTION:Since the depth of a lens surface is varied when the distance of radius of a V-block machining part is varied, a lens blank 3 is moved back and forth with respect to a V-block machining peripheral groove 1a by the moving distance DELTAh of a lens surface. Then, in order to know the moving distance DELTAh of the lens surface at the time of variation in the distance of radius of cutting point, the distance of radius is obtained by an arithmetic unit, from an angle between the contact point between a pattern 23 and the peripheral surface of a copying board 44, and a line connecting the lens center of the pattern 23 to the center of curvature of the peripheral surface of a copying board 444, i.e., a contact point angle theta. The resulting output is given to the pulse motor of a transferring device and, accordingly, the lens blank 3 can be fed accurately in parallel with a slide shaft by a moving distance DELTAh of the lens surface with respect to the V-block machining peripheral groove 1a, to carry out accurate V-block machining. |
