Free-space laser communication system having six axes of movement

A fine acquisition and tracking system for a free_space laser communication system, comprising:

• A. a centroiding system operating to determine an aiming point for the free_space laser communication system;
• B. at least one communication laser operable to generate an output laser beam to be directed at the aiming point;
• C. a steering mirror disposed relative to the centroiding system and the communication laser and configured to direct an incoming beacon beam to the centroiding system and the output laser beam to the aiming point;
• and
• D. a feedback control receiving information on the aiming point from the centroiding system and adjusting the steering mirror to direct the output laser beam at the aiming point according to the information.

A method for fine acquisition and tracking of a beacon beam and aiming of at least one communication laser in a free-space laser communication system, comprising:

• (a) using a steering mirror to direct an incoming beacon beam to a centroiding system;
• (b) using the centroiding system to determine an aiming point for the free-space laser communication system;
• and
• (c) adjusting the steering mirror to direct an output beam at the aiming point determined by the centroiding system.

A laser communication device for free-space communication with another laser communication device, comprising:

• (a) a first adjustable mount engaged to a base unit and operable to rotate about two axes of movement with respect to the base unit;
• (b) a second adjustable mount engaged to the first adjustable mount and operable to rotate about two axes of movement with respect to the first adjustable mount;
• (c) at least one communication laser fixed to the second adjustable mount and configured to produce an output communication laser beam that is modulated to carry information;
• (d) two tracking lasers fixed to the second adjustable mount and configured to produce a first output tracking beam and a second output tracking beam of different fields of view;
• (e) a first sensing array fixed to the second adjustable mount and configured to receive a first incoming tracking laser beam from another laser communication device and to produce a first electrical signal to indicate a first tracking beam position of the first incoming tracking laser beam on the first sensing array;
• (f) a first tracking circuit connected to the first sensing array to receive the first electrical signal, the first tracking circuit comparing the first tracking beam position to a predetermined first boresight position on the first sensing array to produce a first tracking signal which indicates a deviation of the first tracking beam position from the first boresight position;
• and
• (g) a steering mirror engaged to rotate about two axes of movement with respect to the second adjustable mount and located to direct the first incoming tracking laser beam to the first sensing array and direct the output communication laser beam to the other laser communication device, thereby providing six degrees of movement in directions of the first incoming tracking laser beam and the output communication laser beam relative to the base unit,
• wherein the steering mirror is configured to respond to the first tracking signal and reorientate to move the first tracking beam position towards the first boresight position on the first sensing array, thereby directing the output communication laser beam to the other laser communication device.