Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-01-28
2001-10-16
Chan, Jason (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C359S199200, C359S199200
Reexamination Certificate
active
06304354
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to satellite communication systems and more particularly to laser satellite communication systems wherein data is transmitted to, and/or from a satellite using lasers.
As is known in the art information is sometimes transmitted between various locations on the earth by routes which include satellites. More particularly, in the routing process, information may be transmitted from a ground station along the route to a satellite. The receiving satellite may, in some arrangements, retransmit the information to a remote ground station along the route. In other arrangements, the receiving satellite may be retransmit the information directly to another satellite along the route, which, in turn may itself retransmit to another satellite, or to a remote ground station. The transmission path, or data link, directly between a pair of satellites is sometimes referred to as an inter-satellite cross link in the routing process. While transmission of data between the ground station and satellite is typically by radio frequency (RF) energy, the use of laser energy, at least for communication between satellites (i.e., for the inter satellite cross links) offers distinct advantages over radio frequency (RF) systems, particularly for satellites cross links. These advantages include the potential for a great reduction in weight, power for a given data rate, lack of optical spectral congestion and frequency allocation requirements, immunity to electromagnetic interference, co-located transmitters and RF jammers.
SUMMARY OF THE INVENTION
In accordance with the present invention, a laser communication system adapted for use in a satellite communication system is provided. The satellite carries a laser communication system. The laser communication system includes a plurality of active and passive optical elements packaged in a monolithic, or single block, structure for interfacing between a focusing telescope of the satellite and laser transmitters/receivers of the laser communication system. Laser energy is directed between the telescope and the transmitters/receivers by the active and passive optical elements, such laser energy passing through the monolithic structure solely as collimated light. An this way, relay elements, such as diffractive optics and focusing lenses, and their concomitant alignment requirements, are eliminated from the monolithic structure.
In accordance with another feature of the invention, the monolithic structure is configured to provide all optic axes between the telescope and a laser transmitter/receivers in substantially a common plane. More particularly, the laser communication system includes an acquisitin laser transmitter and an acquisition receiver used to enable the satellite to link up with another satellite, or ground station, during an acquisition mode, and a communication laser transmitter and an communication receiver used to enable the satellite to exchange data with the linked up satellite, or ground station. The monolithic structure is configured to dispose the optic axes between the telescope and laser acquisition and communication lasers and the optic axes between the telescope and the acquisition and communication receivers in substantially a common plane. With such an arrangement, the structural rigidity and hence optical integrity of the monolithic structure is improved.
In accordance with an additional feature of the invention, a single detector is provided for both the acquisition mode and a subsequent tracking mode. More particularly, the laser communication system includes a tracking laser transmitter and a tracking receiver used to enable the satellites to track each other during the tracking mode and thereby maintain the link up with the other satellite, or ground station, after the above described acquisition mode. The satellites communicate with one another during the tracking mode. In a preferred embodiment of the invention, a single charge coupled device (CCD) is used for both acquisitive and tracking.
In accordance with still another feature of the invention, a collimating/beam shaping module is provided having affixed thereto a pair of submodular units. More particularly, as noted above, the laser's light passes through the monolithic structure solely as collimated light. In passing between a laser in the system and the monolithic structure, the laser's light beam must shaped and collimated. The first submodular unit includes the laser and a properly aligned beam shaping lens. The second submodular unit includes a mounted collimating lens. The first and second submodular units are aligned with each other and then affixed to each other to provide the collimating/beam shaping module. Next, the collimating/beam shaping module is affixed to the monolithic structured. With such arrangement and method proper accurate alignment of the mounted laser, beam shaping lenses and collimating lens is facilitated.
In accordance with still another feature of the invention, a filter is provided on a surface of the second submodular unit. The filter protrudes beyond the second submodular unit and is provided with a surface adapted to interface, and be affixed to, a surface portion of the monolithic structure.
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Chan Jason
Fish & Richardson P.C.
Sedighian M. R.
The Mitre Corporation
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