| 摘要 |
PCT No. PCT/SE81/00266 Sec. 371 Date May 17, 1982 Sec. 102(e) Date May 17, 1982 PCT Filed Sep. 17, 1981 PCT Pub. No. WO82/01078 PCT Pub. Date Apr. 1, 1982.An instrument for marking leading lines, comprising a front screen and a behind screen (1,2,15,16), which include opaque lines (3) separated by transparent interstices (4), whereby an interference pattern, a so-called moiré pattern, arises when viewing the instrument. The screens have different division, i.e. different distances between the opaque lines. According to the invention, each of the screens (1,2,15,16) comprises a plate, which at its center is bent to an obtuse angle (v), which screen plates are positioned by means of attachment means (6,7,8) so that the obtuse angles (v) face toward each other, in which case the front screen plate (1) is provided with a denser screen division than the behind screen plate (2), or alternatively so that the obtuse angles (v) face away from each other, in which case the front screen plate (15) is provided with a sparser screen division than the behind screen plate (16). |
