| 摘要 |
An optical system provides guidance in the form of a modulated beam for a beamrider missile. The system comprises first and second zoom type optical subsystems providing guidance to the missile when an exhaust plume from a rocket engine is difficult to penetrate. The first optical subsystem PATH D is utilized in a closed loop servo system for positioning a mirror 9 gimballed about two axes, such that it continuously tracks the missile. The second optical subsystem PATH C, along which the beam is directed, comprises negative 12 and positive 13 optical groups forming a defocusable beam expander. These groups 12, 13 are initially defocused. During flight, the negative group 12 is moved away from the positive group 13, toward the focussed position, maintaining, via mirror 9, a constant beam diameter. The positive and negative groups 12, 13 are free of spherical aberration and coma, such that the shape of the beam is not disturbed in any zoom position. |
