Photopic detector system and filter therefor

• US 7,095,009 B2
• Filed: 05/21/2002
• Issued: 08/22/2006
• Est. Priority Date: 05/21/2002
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Wheatley, John A., Harada, Takashi, Ouderkirk, Andrew J., Nevitt, Timothy J., Mizuno, Kazuhiko
• Primary Examiner(s): Luu, Thanh X.
• Assistant Examiner(s): Sohn, Seung C.
• Application Number:
  US10/152,546
• Publication Number:
  US 20030218123A1
• Time in Patent Office: 1,554 Days
• Field of Search: 250/226, 250/208.1, 250/214.R, 359/359, 359/588, 359/589, 356/419
• US Class Current: 250/226
• CPC Class Codes: G01J 1/42 using electric radiation detectors optical or mechanical part G01J1/04; by comparison with a reference light or electric value G01J1/10
• CPC Class Codes: G01J 3/51 using colour filters
• CPC Class Codes: G02B 5/22 Absorbing filters G02B5/201 - G02B5/208 take precedence

Abstract

A detector system, filter therefor, and method of making same is disclosed. The filter includes an interference element having a reflection band disposed primarily in the near infrared, and having a high transmission over most of the visible region. The filter also includes an absorptive element that absorbs light non-uniformly over the visible region. The filter when combined with a semiconductor photodiode or other suitable detector yields a detector system whose spectral responsivity closely matches the visual response of the human eye.

Claims

1. A filter suitable for use with a detector, the filter comprising:

an interference element that substantially reflects normally incident light over a band of near-infrared wavelengths and that substantially transmits normally incident light over visible wavelengths; and

an absorptive element that absorbs light non-uniformly over visible wavelengths, the absorptive element comprising a colorant dispersed in a polymeric matrix;

wherein the filter when combined with the detector yields a detector system whose relative response approximates a visual response of the human eye.

2. The filter of claim 1, wherein the interference element transmits at least about 70% of normally incident light on average between about 400-700 nm.

3. The filter of claim 2, wherein the interference element transmits less than about 5% of normally incident light between about 700-1100 nm.

4. The filter of claim 3, wherein the interference element transmits less than about 2% of normally incident light between about 700-1100 nm.

5. The filter of claim 1, wherein the band of near-infrared wavelengths has a short-wavelength band edge disposed at a wavelength between about 600-850 nm.

6. The filter of claim 1, wherein at least one of the interference element and the absorptive element is disposed on a frame adapted to receive the detector.

7. The filter of claim 1, wherein the colorant comprises at least one pigment.

8. The filter of claim 7, wherein the at least one pigment comprises a green pigment.

9. The filter of claim 8, wherein the at least one pigment further comprises at least one yellow pigment.

10. The filter of claim 1, further comprising a diffuser.

11. The filter of claim 1, wherein the detector comprises a silicon photodiode.

12. The filter of claim 1, wherein the relative response deviates from the photopic response of the human eye by an average of less than about 20%.

13. The filter of claim 1, wherein the interference element comprises a laminate structure, and the absorptive element is at least partially disposed in at least one layer of the laminate structure.

14. The filter of claim 13, wherein the laminate structure comprises an adhesive layer and wherein the absorptive element is disposed in the adhesive layer.

15. A detector system, comprising the filter of claim 1 in combination with the detector.

16. The detector system of claim 15, wherein at least a portion of the absorptive element is disposed on the detector.

17. The detector system of claim 15, wherein the interference element is spaced apart from the detector.

18. The detector system of claim 15, further comprising a filter housing, and wherein the interference element is connected to the filter housing.

19. The detector system of claim 18, further comprising a potting material between the detector and the interference element, and wherein the potting material comprises at least a portion of the absorptive element.

20. The detector system of claim 15, further comprising a filter housing, and wherein at least a portion of the filter housing comprises at least a portion of the absorptive element.

21. A method of making a filter suitable for use with a detector, the method comprising:

providing an interference element that reflects normally incident light over a band of near-infrared wavelengths and substantially transmits normally incident light over visible wavelengths;

loading an absorptive colorant that absorbs light non-uniformly over visible wavelengths into a resin;

shaping the resin to form an absorptive element; and

combining the interference element and the absorptive element to provide the filter;

wherein the filter when combined with the detector yields a detector system whose relative response for normally incident light approximates a visual response of the human eye.

22. The method of claim 21, wherein the relative response deviates from the photopic response of the human eye by an average of less than about 20%.

23. The method of claim 21, wherein the method comprises forming a film of the resin on a substrate.

24. The method of claim 23, wherein the substrate comprises the interference element.

25. The method of claim 23, wherein the substrate comprises the detector.

26. The method of claim 21, wherein the method comprises connecting the interference element to a filter frame.

27. The method of claim 26, wherein the filter frame is at least partially transparent and comprises the colorant-loaded resin.

28. The method of claim 26, wherein the filter frame has a cavity to receive the detector, and wherein the method comprises placing a potting material that comprises the colorant-loaded resin into the cavity and inserting the detector into the cavity.

29. The method of claim 21, wherein the providing step comprises forming a laminate structure, and at least one layer of the laminate structure comprises the colorant-loaded resin.