| 摘要 |
<p>PCT No. PCT/GB91/00157 Sec. 371 Date Sep. 4, 1992 Sec. 102(e) Date Sep. 4, 1992 PCT Filed Feb. 4, 1991 PCT Pub. No. WO91/11745 PCT Pub. Date Aug. 8, 1991.The invention relates to optical elements, particularly retro-reflecting, retro-imaging and optical transmission inversion elements to relay a true scale equal conjugate image of a scene. Hitherto, the image had a resolution limit set by the pitch and/or packing density of micro-optical elements to reflect or transmit ray bundles impinging on them, the number of elements within the viewing zone determining the lateral and hence depth resolution in any given direction. The object of the invention is to reduce the effect of micro-screen texture in a relatively inexpensive manner, that provides real-time systems and which can be used with fast moving objects. This objective is met by an optical element comprising a retro-reflecting or auto-collimating transmission screen (9) having one or more lenses (6,10) and an associated means (8,11) of displacing wavelengths to different degrees and whereby to spread a reflected or transmitted image into a spectral streak. The means (8,11) of displacing wavelengths may be a grating, mechanically or optically blazed, or formed from prisms, or may be a diffraction or zone plate.</p> |
