Optical free space signalling system

A signalling system comprising first and second signalling devices,

• wherein the first signalling device comprises an optical device according to any preceding claim, wherein each of the plurality of emitters of the first signalling device is operable to emit a respective light beam carrying information;
• and
• wherein the second signalling device comprises:
• i) a lens system for collecting light emitted from a light emitter of said first signalling device;
• ii) a light detector for receiving the collected light from said lens system and for converting the received light into corresponding electrical signals;
• and iii) means for processing the electrical signals from said light detector to retrieve said information.

A signalling method using first and second signalling devices, the method comprising the steps of:

• at the first signalling device:
• i) optically locating a plurality of light emitters substantially at a focal plane of a telecentric lens system;
• ii) emitting light carrying information from at least one light emitter from said plurality of light emitters;
• and iii) collecting light emitted from the at least one light emitter using the telecentric lens system and directing the light in a respective direction within the field of view of the telecentric lens system;
• and
• at the second signalling device:
• i) collecting light emitted from the light emitter of the first signalling device using a lens;
• ii) receiving the collected light on a light detector and converting the received light into corresponding electrical signals;
• and iii) processing the electrical signals from the light detector to retrieve the information.

A signalling method using first and second signalling devices, the method comprising the steps of:

• at the first signalling device:
• i) optically locating a plurality of light emitters substantially at a focal plane of a telecentric lens system;
• ii) using at least one light emitter from said plurality of light emitters to emit light carrying information;
• iii) collecting the light emitted by the at least one light emitter using the telecentric lens system and directing the collected light in a respective direction within the field of view of the telecentric lens system;
• at the second signalling device:
• i) using a lens to collect the light emitted from the at least one light emitter of the first signalling device;
• ii) reflecting the collected light from the lens back to the first signalling device through the lens;
• and iii) modulating the light collected by the lens system and/or the reflected light with modulation data for the first signalling device;
• and
• at the first signalling device:
• iv) collecting the modulated light beam which is reflected back from the second signalling device using the telecentric lens system;
• v) receiving the collected modulated light on a light detector and converting the received light into corresponding electrical signals;
• and vi) processing the electrical signals from the light detector to retrieve the modulation data.