Interferometric thermal detector
AssigneeSanta Barbara Research Center
InventorsSteven E. Hodges, Gregory L. Tangonan
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Abstract
An interferometric sensor (10) employs a sensing optical fiber (12) and a reference optical fiber (14). The sensing fiber (12) has a coating 16 thereon responsive to radiated thermal energy while the reference fiber is shielded therefrom. Both the sensing and reference fibers are subjected to the same ambient environment so that both fibers are subjected to heating by convection or conduction in essentially the same amounts. As a result, the sensor (10) is substantially nonresponsive to convected or conducted thermal energy while being highly responsive to radiated energy, particularly in the 6-30 micron wavelength region.
Claims15
A method of detecting radiated thermal energy while being substantially unresponsive to convected or conducted thermal energy, said method comprising:
- (a) introducing a coherent light source of a given frequency into proximal ends of a sensing optical fiber and a reference optical fiber;
- (b) placing both fibers substantially in the same ambient environment so that both fibers are subjected to heating by convection or conduction in essentially the same amounts while permitting only the sensing fiber to be subjected to radiated thermal energy, the other fiber being shielded therefrom;
- (c) recombining optical signals from the fibers;
- and
- (d) interferometrically sensing changes in fringe patterns created by the recombined optical signals, the presence of radiated energy causing characteristics of the sensing fiber to become altered so as to change the fringe pattern.
Apparatus for sensing radiated thermal energy while bearing substantially nonresponsive to convected or conducted thermal energy, said apparatus comprising:
- a sensing optical fiber;
- a reference optical fiber;
- light source means for projecting coherent light into proximal ends of said reference and sensing fibers;
- absorption means for absorbing radiated thermal energy and heating said sensing fiber in response thereto so as to alter characteristics of the fiber;
- shield means for shielding the reference fiber from said radiated energy;
- housing means for locating the reference and sensing fibers in substantially the same ambient location so that each fiber can be subjected to heat by convection or conduction in substantially equal amounts;
- and
- interferometric means for detecting fringe patterns created by recombining optical signals in the reference and sensing fibers.
A thermal detector comprising an outer tube having a sensing optical fiber wrapped around an outer surface thereof, and an inner tube located within the confines of the outer tube and having a reference optical fiber wrapped around a surface thereof.
Dependencies are inferred from the claim text.