| 摘要 |
<p>A kinoform optical element (KOE 10, 10', 10'') has different surface relief heights (20, 24) in different zones (14, 14') of the kinoform surface, in order to optimize the first order diffraction efficiency in each zone. By increasing the first order diffraction efficiency, noise as well as ghost image problems may be reduced and contrast and resolution may be enhanced. In an exemplary embodiment, each zone, or even different areas of the same zone, has a non-constant step height (36) that is preferably defined by a predetermined relationship between an optimal step height (d) and an associated predominant angle of incidence associated with that particular zone or area. Since the optimum surface relief is dependent on the angle of incidence of the radiation relative to the orientation of the surface, diffraction efficiency can also be optimized by providing the kinoform with a non-planar surface contour such that all the predominant rays are normal to the active surface, in which case all the steps may have the same height.</p> |
