Fluorescent activated, spatially quantitative light detector

• US 4,371,897 A
• Filed: 04/27/1981
• Issued: 02/01/1983
• Est. Priority Date: 09/02/1980
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Kramer, Charles J.
• Primary Examiner(s): BRITTON, HOWARD W
• Application Number:
  US06/257,694
• Time in Patent Office: 645 Days
• Field of Search: 358/294, 358/293, 358/75, 358/41, 358/300, 250/216, 250/227, 250/228, 250/237 R, 250/578
• US Class Current: 358/474
• CPC Class Codes: G01J 1/58 using luminescence generated by light
• CPC Class Codes: H04N 1/0281 with means for collecting light from a line or an area of the original and for guiding it to only one or a relatively low number of picture element detectors

Abstract

A fluorescent-activated spatially quantitative light detector for sensing light reflected from an information bearing surface, said light detector comprising a generally cylindrical rod containing a fluorescent dye dispersed throughout a generally transparent medium and a photosensor at one end of, and in operative association therewith. The reflected light incident on the light detector is absorbed by said dye and reradiated at the fluorescent wavelength, a portion of this reradiated light reaching the photosensor causing an output signal to be generated.

Claims

1. A fluorescent-activated spatial quantitative light detector comprising

an elongated rod-like member, said member comprising a fluorescent dye molecularly dispersed throughout a generally transparent solid material, and

at least one photosensor in operative association with said member to detect fluorescent light emitted by said member upon exposure to incident light.

2. The apparatus of claim 1 wherein said photosensor is in optical contact with said medium.

3. The apparatus of claim 1 wherein said photosensor is separated from said medium by an air space equal to at least one wavelength of the emitted fluorescent light.

4. The apparatus of claim 1 wherein a photosensor is placed at each end of said member.

5. The apparatus of claim 1 wherein a photosensor is placed at one end of said member and a reflector at the other end.

6. The light detector of claim 1 wherein said rod-like member is a cylindrically tapered rod having said photosensor at one end thereof, said rod diameter increases with increasing distance from said photodetector.

7. The light detector of claim 1 wherein said rod-like member has a parabolic refractive index distribution which is highest in the center and decreases with increasing distance from the center.

8. The apparatus of claim 1 wherein the fluorescent medium absorbs light in the range of from about 65 percent to about 75 percent per centimeter of said medium of the incident light energy per centimeter of said medium.

9. The light detector of claim 1 further including an elongated light source placed in a parallel plane to said rod-like member whereby the spatial variation of light output from said light source is detected.

10. The apparatus of claim 1 wherein said photosensor is coupled to said medium by a plurality of optical fibers.

11. The apparatus of claim 10 wherein the diameter of said rod-like member is different than said photosensor.

12. The light detector of claim 1 wherein said rod-like member is a cylindrical rod and said photosensor is at one end thereof, and further including a reflective coating covering a portion of the surface of said rod.

13. The light detector of claim 12 wherein said reflective coating is of uniform density and has a surface area which generally decreases with decreasing distance to said photosensor.

14. The light detector of claim 12 wherein said reflective coating is apodized to improve uniformity of the signal generated by the photosensor.

15. The light detector of claim 1 further including a transparent cladding which encases said rod-like member.

16. The light detector of claim 15 further including a transparent elongated tube within which said rod-like member is placed.

17. The light collector of claim 16 wherein said tube and said member are separated by an air space.

18. In a flying spot scanning system adapted to raster scan on information bearing surface, a fluorescent-activated light detector for sensing light reflected from said scanned surface, said light detector comprising

a generally cylindrical rod containing a fluorescent dye dispersed throughout a generally transparent medium and a photosensor at one end of, and in operative association therewith,

whereby said reflected light incident on said light detector is absorbed by said dye and reradiated at the fluorescent wavelength, a portion of this reradiated light reaching the photosensor to generate an output signal therefrom.

19. The system of claim 20 further including a spectrum blocking filter placed before said photosensor, said filter blocking those light wavelengths contributing to a non-uniform light signal.

20. The system of claim 18 further including at least one reflective element placed adjacent said information bearing surface and said cylindrical rod, said reflector adapted to focus reflected light from said information bearing surface along the length of said rod.

21. The system of claim 18 further including a specular reflective surface at the end of the rod opposite the photosensor.

22. The system of claim 21 wherein said reflective surface is diffuse.

23. The system of claim 20 further including means to modify the amount of fluorescence produced in said rod proportional to the distance of the incident light from said photosensor so as to increase uniformity of the signal generated by the photosensor.

24. The system of claim 23 wherein said means is a variation in the amount of fluorescent dye along the length of said rod.

25. The system of claim 23 wherein said means is a variation in the cross-sectional area of said rod.

26. The system of claim 23 wherein said means is a variation in the cross-sectional area of the rod aperture.

27. The system of claim 23 wherein said means is a variation in the absorption volume of said rod.

28. The system of claim 23 wherein said means comprises a light absorbing filter placed before the photosensor.

29. The system of claim 23 wherein said means includes means for modulating the scanning beam so as to increase signal intensity at times when the incident beam is furthest from the photosensor.

30. The system of claim 23 further including a beamsplitter element located in the path of the scanning beam upstream of the scanned surface, said beamsplitter reflecting a portion of said scanning beam through a Ronchi-type ruling into a second fluorescent-activated light detector, said second detector producing a plurality of output clocking signals.

31. The system of claim 23 further including electronic data processing means connected to the output of said photosensor.

32. The system of claim 23 wherein said means comprises a reflective coating covering at least a portion of the rod opposite the light entering portion.

33. The system of claim 32 wherein said cylindrical rod is substantially transmissive of said incident light and wherein the reflective coating is tapered towards the photosensor end.

34. The system of claim 32 wherein said cylindrical rod is substantially transmissive of said incident light and wherein said reflective coating is apodized with decreasing density related to decreasing distance to the photosensor.

35. In a flying spot scanning system adapted to raster scan an information bearing surface, a light detector assembly for collecting light reflected from said scanned surface, said light detector assembly comprising

a generally cylindrical, hollow integrating cavity having a first entrance slit aligned with a second exit, re-entry slit disposed adjacent said scanned surface wherein a scanning beam enters the cavity through said first slit, passes through said second slit and is scattered from said scanned surface back into said cavity,

a fluorescent-activated light detector placed within said cavity, said detector comprising an elongated rod-like member containing a fluorescent dye molecularly dispersed throughout a generally transparent medium, said collector further comprising a photodetector optically coupled to said rod-like member,

whereby said light entering said cavity, following multiple diffuse reflections from the interior surfaces of said cavity is absorbed by said dye and scattered throughout said rod-like member, a portion of said light being coupled to said photosensor to provide an output signal representative of said scanned surface.

36. A light detector apparatus comprising at least two fluorescent-activated, spatial qualitative light detectors, each detector comprising an elongated rod-like member containing a fluorescent dye molecularly dispersed throughout a generally transparent medium each of said medium fluorescing in the principle wavelengths of a primary color media each medium provided with a filter medium to permit a narrow band of light to impinge upon said fluorescent medium, each medium emitting fluorescent light upon exposure to light of different wavelengths.

37. The apparatus of claim 36 further including a third light detector incorporating a dye which fluoresces in the principle wavelength of the third primary color.

39. In a copying apparatus having a photoreceptor, means to charge said photoreceptor in preparation for imaging, exposure means for exposing said charged photoreceptor to produce a latent electrostatic image, developing means for developing the latent electrostatic image, transfer means to remove said developed image from said photoreceptor and read means to scan said developed image on said photoreceptor to provide electrical image signals representative of said developed image, said means including an integrated light collector, the improvement comprising an integrated light collector comprising a fluorescent medium in operative association with a light detector.

38. The apparatus of claim 38 or 39 wherein said light detectors are enclosed within an integrating cavity having at least two apertures coordinated to permit a light beam to pass through both apertures to a substrate adjacent said detector, at least one of said apertures adapted to receive light reflected from said substrate into said cavity, each fluorescent medium emitting fluorescent light upon exposure to light of different wavelengths.