| 摘要 |
An interference pattern, a so-called Moire pattern, is produced when it is read. The screens have different distances between the opaque lines, but the lines have the same width in both screens, and likewise the transparent intermediary spaces have the same width within each screen. At least one of the screens is positioned at an obtude angle. Relatively to a central symmetry line, an intermediary space in the one screen is symmetrically orientated centrally to a like space in the other screen. The Moire pattern, on reading from points along the symmetry line, consists of a symmetrical pattern with a central light band surrounded by dark bands. With reading from points at the side of the symmetry line, a pattern with one or more angled bands is indicated and directed, with a point in the requisite movement direction to achieve the desired placing along the symmetry line. |
