| 摘要 |
<p>An afocal beam expansion system and method which achieves the compactness of prior art refractive systems and yet avoids the use of refractive elements with their accompanying beam scattering, adsorption and temperature sensitivity. A pointing reflector (74) is positioned in the beam path between an expansion reflector (72) and a collimating reflector (76). The small diameter input beam is directed onto the expansion reflector (72), which causes it to diverge, reflects off the pointing reflector (74), and reaches the collimating reflector (76). The latter element collimates the beam and reflects it back to the pointing reflector (74), which points the beam along a desired output axis (78). The expansion, pointing and collimating reflectors are positioned relative to each other such that the beam axis is altered upon each reflection from each element. The pointing reflector (74) may be implemented as a plano mirror, or alternately may comprise a convex reflective surface that cooperates with the collimating mirror (76) to fully collimate the expanded beam. The invention is particularly applicable to airborne laser navigational radar terrain avoidance systems.</p> |
