System for distributing and controlling color reproduction at multiple sites

• US 8,537,357 B2
• Filed: 03/08/2010
• Issued: 09/17/2013
• 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., Mongeau, Daniel R.
• Primary Examiner(s): Geisel, Kara E
• Application Number:
  US12/660,937
• Publication Number:
  US 20100231728A1
• Time in Patent Office: 1,289 Days
• Field of Search: 356/402
• US Class Current: 356/402
• 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 having 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 which directs light to the media;

optics for collecting light of said illumination source reflected from said media, in which at least said optics are moveable to scan said media;

at least a spectrograph for providing data representative of said light collected by said optics; and

one or more programs executable by one or more processors to process said data provided by said spectrograph for comparison to reference data, to store said data provided by said spectrograph in a database of historical data, to provide at least information of the grayness of mixtures of colorants for display to a user, and to communicate one or more of said data provided by said spectrograph, said reference data, and said information to one or more other computer systems using a network protocol.

2. The apparatus according to claim 1 wherein said one or more programs further produce one or more color transformations responsive to said data provided by said spectrograph and communicate to said one or more computer systems at least information related to or representative of said one or more color transformations wherein said information related to or representative of said one or more color transformations is useable by said one or more computer systems for color matching.

3. The apparatus according to claim 2 wherein said information related to or representative of said one or more color transformations comprises a gamut filter whose inputs are color values and whose outputs indicate whether input color values are inside or outside of a color gamut.

4. The apparatus according to claim 1 wherein said object represents media and said apparatus further comprises a program to analyze one or more images rendered on media by a rendering device in order to find areas of color for measurement.

5. The apparatus according to claim 1 further comprising one or more programs that provide information of color errors, wherein said information of color errors is provided to color controls of a production system.

6. The apparatus according to claim 1 wherein said optics and said illumination source are configured with respect to said object to reduce the contribution of light due to specular reflections to the light collected by said optics.

7. The apparatus according to claim 1 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 light due to specular reflections to light collected by said optics.

12. The apparatus according to claim 1 wherein at least one of said one or more processors is part of said apparatus and controls said communication and processing of said data.

20. The apparatus according to claim 1 wherein said data provided by said spectrograph or results of processing said data provided by said spectrograph are stored in relation to at least a device identifier.

21. The apparatus according to claim 1 wherein said measurements are expressed in CIE coordinates of color adjusted for illumination and the adjustment is carried out on spectral data of said spectrograph by substituting the spectrum of viewing illumination for the spectrum of the illumination used for measurement.

22. The apparatus according to claim 1 wherein said data provided by said spectrograph are employed to measure spatial uniformity of color of said object.

23. The apparatus according to claim 20 wherein said database of measurements is accessible by said one or more processors and said one or more computer systems.

24. The apparatus according to claim 20 wherein data of said database are used for preparation of a statistical profile of a series of measurements in relation to a tolerance for error expressed in standard color difference units.

25. The apparatus according to claim 1 wherein said reference data comprise colorimetric values derived from measurement of a calibration standard.

29. The apparatus according to claim 5 wherein said apparatus is integrated into said production system.

30. The apparatus according to claim 29 wherein said object is measured in at least two spatial dimensions.

31. The apparatus according to claim 25 wherein said calibration standard is internal to said apparatus.

32. The apparatus according to claim 1 wherein said reference data comprise a colorimetric specification of a desired color of or on said object.

34. The apparatus according to claim 1 wherein said illumination source is a xenon lamp and said spectrograph is a dual beam spectrograph.

8. A method for measuring color comprising the steps of:

providing illumination to a surface;

collecting light of said illumination reflected from said surface with the aid of optics while scanning said surface;

measuring said collected light with a spectrograph to provide data representative of said light collected by said optics in accordance with a calibration enabling CIE colorimetry traceable to a standard;

processing said data provided by said spectrograph for comparison to reference data, said reference data comprising at least a colorimetric specification of desired colors;

storing said data provided by said spectrograph in a database of measurements in association with time of measurement information;

displaying information of the grayness of a color to a user; and

communicating said data provided by said spectrograph or results of processing said data provided by said spectrograph, and said information to one or more computer systems through a network interface using a network protocol.

9. The method according to claim 8 wherein said steps of processing, storing, displaying and communicating are carried out with the aid of one or more programs executable by a processor.

10. The method according to claim 8 further comprising the steps of:

producing one or more color transformations responsive to said data provided by said spectrograph; and

communicating to said one or more computer systems at least said information related to or representative of said one or more color transformations, wherein said information related to or representative of said one or more color transformations is useable by said one or more computer systems for color matching.

11. The method according to claim 8 wherein said illumination is provided by a source to said surface, and said method further comprises the step of configuring said optics and said illumination source with respect to said surface to reduce the contribution of light specularly reflected from said surface to the light collected by said optics.

13. The method according to claim 8 further comprising the steps of:

producing color error data from said comparison; and

providing said color error data to color controls of a production system.

14. The method according to claim 8 further comprising the step of substituting a viewing illuminant for the measuring illuminant in calculation of color values from spectral measurements.

26. The method according to claim 10 wherein said information related to or representative of said one or more color transformations comprises one of a gamut filter or a chromatic adaptation transform, said gamut filter representing a first data structure stored in a file and accessible through a file header wherein said first data structure has inputs which are color values and outputs indicative of whether input color values are inside or outside of a color gamut, and said chromatic adaptation transform representing a second data structure stored in a file and accessible through a file header to enable conversion of input color coordinates to output color coordinates representative of different viewing conditions.

15. A computer-readable storage medium encoded with a computer program for measurement of color comprising:

one or more programs executable by one or more processors

to process data provided, in accordance with a calibration enabling CIE colorimetry traceable to a standard, by a measurement module for comparison to reference data, said measurement module comprising an array of sensor elements and one of spectrally selective filters or a grating to disperse light into spectral components,

to store said data provided by said measurement module in a database of measurements in association with time of measurement information,

to provide information of the grayness of a color for display to a user, and

to communicate said data provided by said measurement module or results of processing said data provided by said measurement module and said information to one or more computer systems using a network protocol,

wherein said data provided by said measurement module represents measurement of light collected through optics due to reflection or transmission of illumination of a colored object wherein at least said optics are moveable to measure said colored object.

16. The computer-readable storage medium according to claim 15 wherein said one or more programs further produce one or more color transformations responsive to said data provided by said measurement module and communicate to said one or more computer systems at least information related to or representative of said one or more color transformations wherein said information related to or representative of said one or more color transformations is useable by said one or more computer systems for color matching.

17. The computer-readable storage medium according to claim 15 further comprising one or more programs that provide information of color errors for use by color controls of a production system, wherein said reference data comprise a colorimetric specification of a desired color of said colored object and said information of color errors is based upon said comparison.

18. The computer-readable storage medium according to claim 15, wherein said colored object comprises media bearing one or more color images, further comprising a program to analyze said one or more color images rendered on said media in order to find areas of color for measurement.

19. The computer-readable storage medium according to claim 15 further comprising a program enabling substitution of the spectrum of viewing illumination for the spectrum of the illumination used for measurement in the calculation of color values when said data provided by said measurement module comprise spectral data.

27. The computer-readable storage medium according to claim 16 wherein said information related to or representative of said one or more color transformations comprises one of a gamut filter or a chromatic adaptation transform, said gamut filter representing a first data structure stored in a file and accessible through a file header wherein said first data structure has inputs which are color values and outputs indicative of whether input color values inside or outside of a color gamut, and said chromatic adaptation transform representing a second data structure stored in a file and accessible through a file header to enable conversion of input color coordinates to output color coordinates representative of different viewing conditions.

28. The computer-readable storage medium according to claim 15 wherein said reference data comprise colorimetric values derived from measurement of a calibration standard.

33. The computer-readable storage medium according to claim 15 wherein said measurement module provides image data representing a rendered image and wherein color errors are computed by cross-correlating a three-dimensional color histogram derived from said rendered image independently of spatial resolution with a histogram representing the colors desired to be rendered.