Fiber optic infrared sensor

• US 5,712,934 A
• Filed: 07/25/1996
• Issued: 01/27/1998
• Est. Priority Date: 07/25/1996
• Status: Expired due to Term

• Current Assignee: Johnson, Douglas M.
• Original Assignee: Johnson, Douglas M.
• Inventors: Johnson, Douglas M.
• Primary Examiner(s): Palmer, Phan T. H.
• Application Number:
  US08/687,754
• Time in Patent Office: 551 Days
• Field of Search: 385/12, 385/123, 385/13, 385/141, 250/339.11, 250/341.2, 250/341.8, 356/133
• US Class Current: 385/12
• CPC Class Codes: G01F 23/2927 for several discrete levels, e.g. with more than one light-conducting sensing element
• CPC Class Codes: G01M 3/047 with photo-electrical detection means, e.g. using optical fibres
• CPC Class Codes: G01M 3/38 by using light G01M3/02 takes precedence
• CPC Class Codes: G01N 21/474 Details of optical heads therefor, e.g. using optical fibres
• CPC Class Codes: G01N 21/552 Attenuated total reflection

Abstract

There is disclosed an optical sensor comprising a light source, light detector and signal generator, and an optical fiber extending between the light source and detector. The optical fiber includes a sensing length comprising a return bend in the fiber, where the return bend has a bend radius less than or equal to 2.5 times the radius of the optical fiber. In one embodiment, the sensing length further includes a planar sensing surface. A method for detecting the presence of a medium in an environment using the optical sensor of the invention is also disclosed.

Claims

1. An optical sensor, comprising:

(a) a light source for generating light;

(b) a light detector and signal generator for receiving light from the light source and for generating variable signals dependent on the mount of light received; and

(c) an optical fiber made of a light conducting material extending between the light source and the light detector and having a sensing length comprising a return bend in the optical fiber forming an apex, wherein the return bend has a bend radius less than or equal to 2.5 times the radius of the optical fiber.

2. The optical sensor of claim 1, wherein the sensing length further comprises a sensing surface at the apex of the return bend.

3. The optical sensor of claim 2, wherein the sensing surface comprises a planar sensing surface.

4. The optical sensor of claim 3, wherein the sensing surface has a maximum length of about twice the radius of the return bend.

5. The optical sensor of claim 1, wherein the return bend has a bend radius less than or equal to twice the radius of the optical fiber.

6. The optical sensor of claim 1, further comprising a signal processor connected to the light detector and signal generator for output signaling and for indicating the detection of a medium in the environment.

7. The optical sensor of claim 1, wherein the light source is selected from the group consisting of a light-emitting diode, a tungsten light source, and a laser diode.

8. The optical sensor of claim 1, wherein the light source emits light at wavelengths from about 800 nm to about 1200 nm.

9. The optical sensor of claim 1, wherein the light source emits light at wavelengths at about 950 nm.

10. The optical sensor of claim 1, wherein the light detector is selected from the group consisting of a photodiode and a phototransistor.

11. The optical sensor of claim 1, wherein the radius of the optical fiber is from about 50 to about 1000 μ

m.

12. The optical sensor of claim 1, wherein radius of the optical fiber is about 500 μ

m.

13. The optical sensor of claim 1, further comprising a beamsplitter positioned between the light source and the optical fiber sensing length.

14. The optical sensor of claim 1, further comprising an analyte-specific coating on the sensing length.

15. A method for detecting the presence of a medium in an environment comprising contacting a sensing length of an optical sensor with the medium, wherein the optical sensor comprises:

(a) a light source for generating light;

(b) a light detector and signal generator for receiving light from the light source and for generating variable signals dependent on the amount of light received;

(c) an optical fiber made of a light conducting material extending between the light source and the light detector and having a sensing length comprising a return bend in the optical fiber forming an apex, wherein the return bend has a bend radius less than or equal to 2.5 times the radius of the optical fiber; and

(d) processing means connected to the light detector and signal generator for output signaling and for indicating the detection of a medium in the environment, such that the presence of the medium in the environment is detected.

16. The method of claim 15, wherein the sensing length comprises a planar sensing surface at the apex of the return bend.

17. The method of claim 16, wherein the sensing surface has a maximum length of about twice the radius of the return bend.

18. The method of claim 15, wherein the return bend has a bend radius less than or equal to about twice the radius of the optical fiber.

19. The method of claim 15, wherein the light source emits light at a wavelength of about 950 nm.

20. The method of claim 15, wherein the radius of the optical fiber is about 500 μ

m.

21. The method of claim 15, wherein the optical sensor further comprises a beamsplitter positioned between the light source and the optical fiber sensing length.

22. The method of claim 15, wherein the medium is water.

23. The method of claim 15, wherein the medium is a hydrocarbon.

24. The method of claim 15, wherein the medium is a hydrocarbon in water.

25. An optical sensor, comprising:

(a) a light source for generating light;

(b) a light detector and signal generator for receiving light from the light source and for generating variable signals dependent on the amount of light received; and

(c) an optical fiber made of a light conducting material extending between the light source and the light detector and having a sensing length comprising a return bend in the optical fiber forming an apex, wherein the return bend has a bend radius less than or equal to 2.5 times the radius of the optical fiber, wherein the sensing length further comprises a planar sensing surface at the apex of the return bend, and wherein the planar sensing surface has a maximum length of about twice the radius of the return bend.

26. The optical sensor of claim 25, wherein the radius of the optical fiber is from about 50 to about 1000 μ

m.

27. The optical sensor of claim 25, further comprising a beamsplitter positioned between the light source and the optical fiber sensing length.

28. The optical sensor of claim 25, further comprising an analyte-specific coating on the sensing length.

29. The optical sensor of claim 25, further comprising a signal processor connected to the light detector and signal generator for output signaling and for indicating the detection of a medium in the environment.

30. A method for detecting the presence of a medium in an environment comprising contacting a sensing length of an optical sensor with the medium, wherein the optical sensor comprises:

(a) a light source for generating light;

(b) a light detector and signal generator for receiving light from the light source and for generating variable signals dependent on the amount of light received;

(c) an optical fiber made of a light conducting material extending between the light source and the light detector and having a sensing length comprising a return bend in the optical fiber forming an apex, wherein the return bend has a bend radius less than or equal to 2.5 times the radius of the optical fiber, wherein the sensing length comprises a planar sensing surface at the apex of the return bend, and wherein the planar sensing surface has a maximum length of about twice the radius of the return bend; and

(d) processing means connected to the light detector and signal generator for output signaling and for indicating the detection of a medium in the environment, such that the presence of the medium in the environment is detected.

31. The method of claim 30, wherein the optical sensor further comprises a beamsplitter positioned between the light source and the optical fiber sensing length.

32. The method of claim 30, wherein the medium is water.

33. The method of claim 30, wherein the medium is a hydrocarbon.

34. The method of claim 30, wherein the medium is a hydrocarbon in water.

35. The method of claim 30, wherein the radius of the optical fiber is about 500 μ

m.