| 摘要 |
Light from a light source (8) is modulated by several grids (4,1) which can be displaced relative to one another causing deflected light beams to interfere with one another. Several photo-detectors (6,7) are used to form signals phase displaced from one another and at least one of the grid has several diagonal grid zones arranged one behind the other (2,3) with identical or only insignificantly different diagonal pitch periods (TT). Each of the grid zones has periodic markings spaced diagonally apart and the grid zones are arranged phase displaced from one another across the direction of measurement. This phase displacement differs from 180 degrees and the part beams diagonally deflected at these markings are directed at the photo-detectors. |
