| 摘要 |
<p>946, 339. Gauges with optical reading heads. TECHNICOLOR Ltd. May 21,1962 [May 23, 1961], No. 18632/61. Headings G1J and G1M. A reading head for the scale of a measuring apparatus comprises a stack of laminar plates having thickness equal to (or a simple fraction of) the width ("pitch") of a scale marking 23 - this being of the same width as the space 24 between markings - alternate laminae, as shown in Fig. 2 and corresponding to the markings and spaces respectively, being staggered (Fig. 1) so that light entering a first window at the bottom of each lamina (adjacent the scale) and leaving, after interval reflections, through a second window at the top, will pass to separate photo-detecting or visual observing means 26, 27 associated respectively with light from the markings and light from the spaces. The visual observing means may utilize different colours or different areas of illumination. On movement of the scale the intensity at each detector will vary, passing through one "phase" cycle (360 degrees) for a shift of one division. The faces of the laminae, and the edges (20c, 20d and 21c, 21d) not forming the windows, may be rendered reflecting by deposition of a metal or a substance of high refractive index. Alternatively, the laminae may be shaped to provide internal reflection by critical incidence. As shown in Figs. 1 and 2, the scale is transparent and illuminated from below with an opaque scale, a third window 41 (Fig. 5) may be formed on each lamina for introducing external light to the scale via the first window. Opaque spacers are provided between adjacent laminae. Various other arrangements are described for separating the light from the markings and that from the spaces such as imparting different amounts of refraction (Figs. 6 and 7) to the emergent beams. As shown in Fig. 10 the laminae have flexible light-transmitting extensions 51 for guiding light to the two detectors. Instead of using a stack of laminae arranged transversely to the length of the scale, laminae may be used extending lengthwise over the scale (Fig. 12) and having a plurality of windows. There may be several groups of laminae, those of one group being interleaved with those of other groups, to give a number of signals at different phases. The number of laminae per scale division may be a simple integer or fraction, or may differ slightly to provide vernier action.</p> |
