Remote sensing

A method for remotely sensing light emanating from within a monitored environment to detect a property of the monitored environment, the method comprising:

• receiving, at a detector, from one or more retro-reflective optical elements light returned by an optically reflective optical coating in response to a beam of light being directed at the optical element(s), the optical elements bearing the optical coating upon a surface thereof and positionable within the environment to be monitored;
• and,
• detecting, by the detector, a property of the monitored environment according to said returned light, the property comprising one or more of temperature, pressure, and/or salinity;
• wherein an individual optical element includes a body comprising a focuser part of positive optical power partly surrounded by a reflector part separated therefrom and connected thereto across an open spacing, and wherein the optical coating is arranged over an outer surface of the reflector part thereat to receive light which has been at least partially converged by the focuser part for subsequent retro-reflection.

A system for remotely sensing light emanating from within a monitored environment, the system comprising:

• a retro-reflective optical element positionable within the environment to be monitored;
• a light source arranged to direct a beam of light at the optical element;
• and
• a detector arranged to receive from the optical element light returned by the optical element in response to the beam of light;
• wherein said optical element includes a body comprising (i) a focuser part of positive optical power, (ii) a reflector part partially surrounding the focuser part and at least in part separated from the focuser part by an open spacing, and (iii) one or more spacers connected to both the focuser part and the reflector part,
• wherein the optical element bears a photo-luminescent material over at least a part of a surface of the reflector part,
• wherein at least a part of the photo-luminescent material and/or at least a part of the focuser part is coated by anti-reflective optical coating, and
• wherein the photo-luminescent material arranged over at least the part of the surface of the reflector part is to (i) receive light which has been at least partially converged by the focuser part and (ii) retro-reflect the received light.