Photopic detector system having a filter with an interference element, an absorptive element and an absorber or reflector

• US 7,075,056 B2
• Filed: 05/21/2003
• Issued: 07/11/2006
• Est. Priority Date: 05/21/2002
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Harada, Takashi, Wheatley, John A., Ouderkirk, Andrew J., Nevitt, Timothy J., Mizuno, Kazuhiko
• Primary Examiner(s): Le, Que T.
• Application Number:
  US10/515,352
• Publication Number:
  US 20050224703A1
• Time in Patent Office: 1,147 Days
• Field of Search: 250/226, 250/208.1, 250/214.R, 250/214.1, 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 detector system comprising:

a detector having a detector response with a long wavelength end; and

a filter that includes;

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, wherein the band has a long wavelength band edge that moves to an oblique-angle shifted band edge for oblique angle incident light;

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

an absorber or reflector suitable to substantially block light for wavelengths between the long wavelength end of the detector response and the oblique-angle shifted band edge;

wherein a relative response of the detector system approximates a visual response of the human eye.

2. The detector system 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 detector system of claim 2, wherein the interference element transmits less than about 5% of normally incident light between about 700–

1100 nm.

4. The detector system of claim 3, wherein the interference element transmits less than about 2% of normally incident light between about 700–

1100 nm.

5. The detector system 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 detector system 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 detector system of claim 1, wherein the colorant comprises at least one pigment.

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

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

10. The detector system of claim 1, further comprising a diffuser.

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

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

15. The detector system of claim 1, wherein at least a portion of the absorptive element is disposed on the detector.

16. The detector system of claim 1, wherein the interference element is spaced apart from the detector.

17. The detector system of claim 1, further comprising a filter frame, and wherein the interference element is connected to the filter frame.

18. The detector system of claim 17, 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.

19. The detector system of claim 1, further comprising a filter frame, and wherein at least a portion of the filter frame comprises at least a portion of the absorptive element.