| 摘要 |
A reflector is arranged so that an output beam and an input beam remain at a constant angle to each other for at least a limited range of angles of incidence of the input beam. The device comprises a thin collimating lens (2) through which the beam passes, a pair of opposed reflectors (4, 8) positioned equal distances on opposite sides of the collimating lens and a tranverse reflector (6). The input beam passes through the lens and, after reflection at one of the opposed reflectors, is focussed at the surface of the transverse reflector and then passes out again through the lens after reflection at the other opposed reflector. The lens may be replaced by a concave mirror or other optical element capable of focussing the input beam and collimating the output beam. The reflectors may be constituted by the surfaces of a solid block of transparent material. <IMAGE>
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