System for distributing and controlling color reproduction at multiple sites

• US 7,710,560 B2
• Filed: 04/28/2006
• Issued: 05/04/2010
• Est. Priority Date: 08/25/1997
• Status: Expired due to Fees

• Current Assignee: RAH Color Technologies LLC
• Original Assignee: RAH Color Technologies LLC
• Inventors: Holub, Richard A.
• Primary Examiner(s): Geisel; Kara E
• Application Number:
  US11/413,949
• Publication Number:
  US 20060197757A1
• Time in Patent Office: 1,467 Days
• Field of Search: 356/305, 356/326, 356/369, 356/402, 356/302, 356/446
• US Class Current: 356/300
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01J 2003/283 computer-interfaced
• CPC Class Codes: G01J 2003/2866 Markers; Calibrating of scan
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/0224 using polarising or depolarising elements
• CPC Class Codes: G01J 3/0262 Constructional arrangements for removing stray light
• CPC Class Codes: G01J 3/0291 Housings; Spectrometer accessories; Spatial arrangement of elements, e.g. folded path arrangements
• CPC Class Codes: G01J 3/1838 Holographic gratings
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 3/46 Measurement of colour; Colour measuring devices, e.g. colorimeters measuring colour temperature G01J5/60
• CPC Class Codes: G01J 3/462 Computing operations in or between colour spaces; Colour management systems
• CPC Class Codes: G01J 3/463 Colour matching
• CPC Class Codes: G01J 3/465 taking into account the colour perception of the eye; using tristimulus detection
• CPC Class Codes: G01J 3/505 measuring the colour produced by lighting fixtures other than screens, monitors, displays or CRTs
• CPC Class Codes: G01J 3/51 using colour filters
• CPC Class Codes: G01J 3/524 Calibration of colorimeters
• CPC Class Codes: G03F 7/70058 Mask illumination systems
• CPC Class Codes: G06T 5/40 using histogram techniques
• CPC Class Codes: G06T 5/77 : Retouching; Inpainting; Scratch removal
• CPC Class Codes: G06T 7/90 : Determination of colour characteristics
• CPC Class Codes: G09G 2320/0276 : for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/043 : Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/0606 : Manual adjustment
• CPC Class Codes: G09G 2320/0626 : for control of overall brightness
• CPC Class Codes: G09G 2320/066 : for control of contrast
• CPC Class Codes: G09G 2320/0666 : for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2320/0693 : Calibration of display systems
• CPC Class Codes: G09G 2320/08 : Arrangements within a display terminal for setting, manually or automatically, display parameters of the display terminal
• CPC Class Codes: G09G 5/02 : characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: H04N 1/6055 : using test pattern analysis
• CPC Class Codes: H04N 1/6058 : Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut
• CPC Class Codes: H04N 17/02 : for colour television signals
• CPC Class Codes: H04N 9/643 : Hue control means, e.g. flesh tone control
• CPC Class Codes: H04N 9/646 : for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters
• CPC Class Codes: H04N 9/69 : for modifying the colour signals by gamma correction controlling camera response for colour signals H04N23/83

Abstract

In a color imaging system, multiple rendering devices are provided at different nodes along a network. Each rendering device has a color measurement instrument for calibrating the color presented by the rendering device. A rendering device may be a printer in which the measuring of color samples on a sheet rendered by the printer is provided by a sensor coupled to a transport mechanism which moves the sensor and sheet relative to each other, where the sensor provides light from the samples to a spectrograph. A rendering device may also be a display buying a member supporting a color measuring instrument for receiving light from an area of the screen. The color measuring instruments provide for non-contact measurements of color samples rendered on a display or a sheet, and are self calibrating by the use of calibration references.

Claims

1. An apparatus for measurement of color rendered on media comprising:

an illumination source capable of directing light to the media;

optics enabling collection of light of said illumination source reflected from said media, in which said optics and said media are mechanically moveable with respect to each other; and

at least a spectrograph for receiving and measuring color of said light collected by said optics, wherein said optics are non-contact with said media during measurement by said spectrograph, wherein said optics move perpendicularly to the direction of movement of said media, wherein said media is printed by a printer having a print head, said apparatus is integrated with said printer, and at least said optics is positioned to move in tandem with said print head.

2. The apparatus according to claim 1 further comprising at least one of a computer or processor for receiving one or more measurements made by said spectrograph.

3. The apparatus according to claim 2 wherein said at least one of a computer or processor is capable of receiving color transformation information from a network source and using said information in the rendering of image data by said printer.

4. The apparatus according to claim 2 wherein said one or more measurements are provided in device independent units and said at least one of a computer or processor is capable of computing or modifying a color transformation responsive to said one or more measurements.

5. A method for measuring color samples rendered on media comprising the steps of:

providing illumination of a first polarization to media having one or more color samples;

collecting light of said illumination reflected from said media of each of said one or more color samples with the aid of optics;

scanning said optics and said media with respect to each other to enable said collecting step to be carried out;

measuring said reflected light collected by said optics with at least a spectrograph, in which the light received by said spectrograph is cross polarized by a polarizer element with respect to said first polarization, and said optics are non-contact with said media during measurement by said spectrograph; and

providing at least one sensor for obtaining a reference for calibration of the spectrograph.

6. An apparatus for measurement of color rendered on media comprising:

an illumination source capable of directing light to the media;

optics enabling collection of light of said illumination source reflected from said media, in which said optics and said media are mechanically moveable with respect to each other; and

at least a spectrograph for receiving and measuring color of said light collected by said optics, wherein said spectrograph comprises a sensor array and one or more sensor elements capable of recording one or more references for calibration of said spectrograph.

7. The apparatus according to claim 6 wherein said optics move perpendicularly to the direction of movement of said media.

8. The apparatus according to claim 6 wherein said spectrograph is a dual beam spectrograph.

9. The apparatus according to claim 6 wherein at least one of said one or more references represents a response of said one or more sensor elements to one or more of darkness, changes in said illumination source with time, or light of said illumination source reflected from a reference surface.

10. The apparatus according to claim 6 wherein said spectrograph is an imaging spectrograph.

11. The apparatus according to claim 6 wherein said apparatus is integrated in a hard copy rendering device.

12. The apparatus according to claim 6 wherein one or more of said one or more sensor elements provide a measurement of said one or more references which is indicative of temperature.

13. The apparatus according to claim 6 further comprising a processor for receiving one or more measurements made with said spectrograph, said processor having an interface to a computer system for communicating data representative of said measurements, and one or more programs executable by said computer system for computing or modifying one or more color transformations in accordance with at least said data representative of said measurements.

14. The apparatus according to claim 13 wherein said one or more programs are also capable of producing and analyzing image data responsive to said one or more measurements made with said spectrograph.

15. The apparatus according to claim 6 wherein said optics are non-contact with said media during measurement by said spectrograph.

16. An apparatus for measurement of color rendered on media comprising:

an illumination source capable of directing light to the media;

optics enabling collection of light of said illumination source reflected from or transmitted through said media, in which said media is movable with respect to said optics and at least said optics are moveable with respect to said media;

at least a spectrograph for receiving and measuring color of said light collected by said optics, wherein said optics are non-contact with said media during measurement by said spectrograph and diminish detection of specularly reflected light from said media, wherein said media is mechanically moved upon operation of a switch.

17. The apparatus according to claim 16 wherein said switch represents a pressure sensitive switch.

18. The apparatus according to claim 16 further comprising at least one of a computer or processor capable of receiving one or more measurements made by said spectrograph.

19. The apparatus according to claim 18 wherein said at least one of a computer or processor enables communication of said one or more measurements of said media by said spectrograph to one or more networked sites.

20. The apparatus according to claim 18 wherein said one or more measurements are provided in device independent units.

21. The apparatus according to claim 18 wherein said at least one of a computer or processor is capable of computing or modifying a color transformation responsive to said one or more measurements.

22. The apparatus according to claim 16 further comprising an interface enabling transmission of color data representative of one or more color measurements of said spectrograph to a computer system which executes one or more programs, wherein said one or more programs produce at least one color transformation responsive to said color data and to information descriptive of illumination or viewing conditions.

23. A method for measuring color rendered on media comprising the steps of:

providing illumination to said media;

diminishing detection of light specularly reflected from said media;

collecting light of said illumination reflected from or transmitted through said media with the aid of optics;

sensing the presence of said media with a switch;

scanning said optics and said media with respect to each other to enable said collecting step to be carried out, in which said scanning step is operative in response to said sensing step; and

measuring color of said light reflected from or transmitted through said media with at least a spectrograph during said scanning step.

24. The method according to claim 23 further comprising the step of measuring the homogeneity of color rendering across the surface of said media.

25. The method according to claim 23 further comprising the step of producing an image responsive to said measuring.

26. The method according to claim 23 further comprising the step of computing or modifying a color transformation responsive to said measuring.

27. The method according to claim 23 further comprising the step of providing one or more sensors for obtaining at least one reference for calibration of said spectrograph.

28. The method according to claim 27 wherein said reference represents the response of said one or more sensors to darkness, changes in said illumination source with time, or light of said illumination source reflected from a reference surface.

29. The method according to claim 27 wherein said at least one reference represents a response of said sensor indicative of temperature.

30. The method according to claim 23 further comprising the step of analyzing images which have been rendered on said media.

31. The method according to claim 23 further comprising the step of providing numeric or bar code data on the media with identifying information for said media.

32. The method according to claim 26 wherein said color transformation is in accordance with illumination or viewing conditions.

33. The method according to claim 23 further comprising the step of calculating errors of color reproduction on said media using data representative of said light.

34. The method according to claim 33 further comprising the step of correcting said errors of color reproduction for a device which rendered said media by one or more of modifying linearization curves for one or more color channels of the device, producing a color-to-color'"'"' transformation, or performning full recalibration of the device including computation of color mixture functions when said errors of color reproduction exceed a tolerance.

35. An apparatus for measuring color comprising:

an illumination source capable of directing light to media having one or more color samples;

optics enabling collection of light of said illumination source reflected from or transmitted through said media;

a spectrograph for receiving and measuring color of said light collected by said optics, wherein at least said optics are moveable to scan said media and said optics diminish detection of specular light by said spectrograph;

an interface enabling transmission of color data representative of said one or more color samples from said apparatus to a computer system capable of executing one or more programs, wherein said one or more programs produce at least one color profile responsive to said color data and to information descriptive of viewing conditions; and

an internal reference for calibration of said spectrograph.

36. The apparatus according to claim 35 wherein said spectrograph is an imaging spectrograph.

37. The apparatus according to claim 35 wherein said media has one or more markings to facilitate locating said one or more color samples on said media by said apparatus, or numeric or bar code data providing identifying information for said media.

38. The apparatus according to claim 35 wherein said one or more programs executable by said computer system process data of said spectrograph for comparison to reference data, store measurements in a database of historical data, present at least information of the grayness of mixtures of colorants on said display, and communicate one or more of said data produced by said spectrograph, said reference data, said measurements, and said information to one or more other computer systems through a network interface using Internet Protocol.

39. The apparatus according to claim 38 wherein said one or more programs further communicate said at least one color profile to said one or more other computer systems through said network interface.

40. The apparatus according to claim 35 wherein information of the state of calibration of said apparatus is communicated to one or more other computer systems through a network interface.

41. The apparatus according to claim 35 wherein said one or more programs further provide a graphical user interface enabling a user to view a representation of at least gamut data of one or more rendering devices.

42. The apparatus according to claim 35 further comprising one or more programs executable by said computer system to analyze images which have been rendered on said media.

43. The apparatus according to claim 35 further comprising one or more programs executable by said computer system that provide information of color errors, said information used to control printing variables of a press.

44. The apparatus according to claim 38 wherein said illumination source comprises a first polarizer with a first polarization through which light is directed to said media, said optics having a second polarizer having a second polarization crossed with respect to said first polarization, and said first and second polarizers operate to reduce the contribution of specular reflections of light reflected from said media in light collected by said optics.

45. The apparatus according to claim 35 wherein said one or more programs further produce one or more color transformations responsive to said color data and communicate information of color transformations to one or more other computer systems through a network interface, and said information of color transformations includes at least a data structure whose inputs are color values and whose outputs indicate whether said color values are either in or out of gamut for a color rendering device.

46. An apparatus for measurement of color rendered on media comprising:

an illumination source for directing light to the media;

optics for collecting light of said illumination source reflected from said media in which at least said optics are moveable with respect to said media, wherein said media is scanned in two dimensions;

at least a spectrograph for producing data representative of said light collected by said optics, wherein said optics diminish the contribution of specular reflections in said light collected by said optics;

an interface providing transmission of said data representative of said light to a processor or a computer system; and

one or more programs executable by said processor or computer system which produce one or more color transformations responsive to said data representative of said light and to calibration data of said apparatus, wherein said one or more programs produce a color conversion which is usable for compensating for change in viewing conditions, said one or more color transformations and said color conversion being useable to improve rendering.

47. The apparatus according to claim 46 wherein said apparatus is integrable into a printer.

48. The apparatus according to claim 47 wherein said printer is an ink jet printer which employs more than four colorants.

49. The apparatus according to claim 46 further comprising a sensor whose output provides indications of temperature.

50. The apparatus according to claim 46 wherein the calibration of said spectrograph is verified automatically at least by reference to a standardized reflectance form.

51. The apparatus according to claim 46 further comprising one or more programs executable by said processor or computer system which use said data representative of said light to calculate errors of color reproduction on said media.

52. The apparatus according to claim 51 further comprising one or more programs executable by said processor or computer system which correct said errors of color reproduction by one or more of modifying linearization curves for one or more color channels of a device, producing a color-to-color'"'"' transformation or performing full recalibration of the device including computation of color mixture functions, when errors of color reproduction exceed a tolerance.

53. The apparatus according to claim 46 wherein the state of calibration of said apparatus is verified responsive to a request communicated via a network.

54. The apparatus according to claim 46 wherein said one or more programs further enable graphical representation of the gamuts of one or more color rendering devices.

55. The apparatus according to claim 46 wherein said one or more programs produce a data structure whose inputs are color values and whose outputs indicate whether said color values are either in or out of gamut for a device.

56. The apparatus according to claim 46 wherein said color transformations enable rendering on a device having more than four colorants.

57. The apparatus according to claim 56 wherein a plurality of said more than four colorants are neutral.

59. The apparatus according to claim 46 wherein said illumination source comprises a first polarizer with a first polarization through which light is directed to said media, said optics having a second polarizer having a second polarization crossed with respect to said first polarization, and said first and second polarizers operate to reduce the contribution of specular reflections of light reflected from said media to light collected by said optics.

58. An apparatus for measurement of color rendered on media comprising:

an illumination source for directing light to the media;

optics enabling collection of light of said illumination source reflected from said media, in which said optics and said media are mechanically moveable with respect to each other;

at least a spectrograph for receiving and measuring said light collected by said optics, wherein said optics are non-contact with said media during measurement by said spectrograph and wherein said media is printed upon by a printer, said apparatus is integrable with a printer and at least said optics is capable of scanning said media following printing; and

at least one standardized reflectance form which provides a reference for self-calibration of said spectrograph.

60. The apparatus according to claim 58 further comprising a sensor whose output provides indications of temperature.