| 摘要 |
<p>The invention provides an optical element comprising a first hologram (1) and a second hologram (2) separated by an intervening medium (30). The holograms (1, 2) have the same diffraction spacing and refractive index, but the first hologram (1) has an efficiency about one-half that of the second hologram (2), preferably about 50 % and >95 %, respectively. The geometry and the refractive index of the intervening medium (3) are such that an input beam (B) of mixed light undergoes diffraction and refraction to produce output beams (p1, p2) which combine in a controllably self-cancelling manner. Methods for the production of this element are also described.</p> |
