| 摘要 |
<p>The device is used in optical imaging tubes where it is required to maintain it at a fixed, small distance from a birefringent monocrystal. The grid (11) is in the form of a series of thin equi-spaced parallel wires (12). Glass beads (14) of final dia. are used as supports and spacer elements. If the wire is of sufficient diameter (greater than 100 microns), it can be drawn from a die so as to leave a concave groove (21) in one side. The wire can then fit around the upper side of the glass bead. The spacing of glass beads can be one per centimetre using this technique. Alternatively the wire can be formed with a flattened face on which the beads can make contact. For finer wires, beads can be made to adhere to wire by passing it first through an oven to coat the surface and then, through a second oven to fire the beads on. This technique refines a larger number of beads and results in reduced image resolution.</p> |
