US 5,517,016 AGranted

Lasercom system architecture with reduced complexity

AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration

InventorsJames R. Lesh, Chien-Chung Chen, Homayoon Ansari

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Abstract

Spatial acquisition and precision beam pointing functions are critical to spaceborne laser communication systems. In the present invention a single high bandwidth CCD detector is used to perform both spatial acquisition and tracking functions. Compared to previous lasercom hardware design, the array tracking concept offers reduced system complexity by reducing the number of optical elements in the design. Specifically, the design requires only one detector and one beam steering mechanism. It also provides means to optically close the point-ahead control loop. The technology required for high bandwidth array tracking was examined and shown to be consistent with current state of the art. The single detector design can lead to a significantly reduced system complexity and a lower system cost.

Claims15

Dependent claims

A tracking apparatus for precision beam pointing in a laser communication system, the apparatus comprising:

a telescope for receiving a distant source of reference light and for transmitting modulated laser light, said telescope having an optical axis;
a focal plane detector array positioned to intersect said optical axis;
a beam splitter positioned at said optical axis between said telescope and said focal plane array, said beam splitter being partially transmissive and partially reflective to incident light that is substantially perpendicular to said optical axis;
a retro-mirror positioned on one side of said beam splitter and displaced from said optical axis;
a beam-steering mirror positioned on another side of said beam splitter opposite from said retro-mirror and displaced from said optical axis;
a source of modulated laser light forming a light beam incident on said beam-steering mirror, said light beam being reflected by said beam-steering mirror onto said beam splitter, a first portion of said light beam being reflected by said beam splitter into said telescope for transmission toward said reference light, a second portion of said light beam being transmitted by said beam splitter onto said retro-mirror, being reflected by said retro-mirror back to said beam splitter and being reflected by said beam splitter to said detector array, the distance between an image of said reference light on said focal plane array and an image of said second portion of said light beam on said focal plane array being a direct measure of the relative angular offset between the reference light and the transmitted first portion of said light beam.

3 more elements

Dependencies are inferred from the claim text.