| 摘要 |
<p>To be useful in image projection systems, white light beams should be well-collimated and have a uniform light intensity. To use a reflector, such as a parabolic reflector, to generate such a beam, a conical prism lens (or other optical system) placed in the beam acts to eliminate a hole in the beam produced by a shield mounted on the light source. To eliminate the hole the relation between the radius r of the shield, the conical prism lens thickness h, the index of refraction n of the conical prism lens, and the angle ζ between the outside surface of the conical prism lens and the radial direction is: r ≈ h*sinζ*[l - cosζ*(n?2 - sin2ζ)-1/2¿]. To correct for a reduction in light intensity with radial distance, the angle ζ may increase with radius. A Fresnel equivalent of the conical prism lens may be used, and when the illumination plane is sufficiently far from the Fresnel lens, dark bands will not be visible. If a non-parabolic reflector is used, the lens system must include a means for collimating the beam.</p> |
