| 摘要 |
<p>A ball is from D 700x10-6 m to 2500x10-6 m in diameter and has at least one sign engraved in the surface. The sign is constituted by a system of engraved individual cells situated on the surface of a spherical cap of the ball with a base having a circumference OD in the range from 10x10-6 m to 0.5 n D and the diameter Dc of the circle circumscribing the plan view shape of the cell is in the range from 10x10-6 m to 1/7 D, whereby the depth of the cell is in the range from 5x10-6 m to 2xDc.</p> |
