System for distributing and controlling color reproduction at multiple sites

• US 9,057,645 B2
• Filed: 09/30/2014
• Issued: 06/16/2015
• 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:
  US14/501,718
• Publication Number:
  US 20150022808A1
• Time in Patent Office: 259 Days
• Field of Search: 356/300
• US Class Current: 1/1
• 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. A system for capturing a two-dimensional image comprising:

optics for collecting light reflected from, transmitted through or emitted by a surface or a medium;

a measurement module comprising a two-dimensional array of sensor elements and a concentric optical element having a grating that provides to said array of sensor elements a spectral dispersion of said light collected by said optics, wherein said array of sensor elements records a spectral distribution of said light collected by said optics at each point along a line through an image of said surface or medium, wherein movement of said at least one of at least said array of sensor elements, or said surface or medium, enables capture of a plurality of ones of said line;

said system operates in calibration to a reference traceable to a standard;

one or more processors to control said measurement module and to provide an interface to an external system;

and

software executable by one or both of said one or more processors or said external system comprising;

a program for computing, based upon each said spectral distribution, values of one or more variables that provide a representation of said spectral distribution, wherein said one or more variables are utilized at least in rendering a visual representation of said image;

a program that enables communication of at least said values of said one or more variables through said interface to said external system; and

a program for storing said at least said values of said one or more variables along with information having at least a time of capture of said image.

2. The system according to claim 1 wherein said reference for calibration is incorporated in said system.

3. The system according to claim 1 wherein said external system comprises a computer system having memory for storing said one or more variables and the time of capture of said image in a database along with information identifying a source of said one or more variables.

4. The system according to claim 1 wherein said one or more variables representative of a point on said image have values comparable to desired values for a plurality of said points to provide information utilized for quality control.

5. The system according to claim 3 wherein said software further comprises a program that prepares one or more histograms comprising a plurality of said values associated with said one or more variables for comparison to one or more corresponding histograms comprising desired values.

6. The system according to claim 5 wherein said software further comprises a program that computes differences between said one or more histograms and said one or more corresponding histograms and compares said differences to an error criterion.

7. The system according to claim 6 wherein information related to said differences is utilized for process control in a production system.

8. The system according to claim 3 wherein said rendering is responsive to user-modifiable tonal transfer curves for one or more channels of a color rendering device.

9. The system according to claim 1 wherein said program for computing said values of said one or more variables convolves said spectral distribution with one or more spectral functions corresponding, respectively, with each of said one or more variables.

10. The system according to claim 9 wherein said one or more spectral functions are related to human color sensitivity.

11. The system according to claim 10 wherein said visual representation of said image is prepared with the aid of at least one color profile, said color profile comprising one or more color transformations and fields identifying said one or more color transformations in which said one or more color transformations comprise at least a conversion of said values of said one or more variables into device dependent coordinates for said rendering.

12. The system according to claim 1 further comprising references enabling estimation of dark current of the sensor array and verification of wavelength calibration of said measurement module.

13. The system according to claim 10 wherein said measurement module further comprises an input that enables measurement of the spectral distribution of light incident upon said surface or medium, said measurement useful for representation of the colors of an image of said surface or medium under different conditions of illumination.

14. The system according to claim 1 further comprising a line camera, operable in concert with said two-dimensional array of sensor elements, in which said line camera provides higher spatial resolution of image capture than said two dimensional array of sensor elements, wherein images captured by said system are stored in a hierarchical multi-resolution format.

15. The system according to claim 1 further comprising variable focus and compensation for aliasing in signal processing.

16. A method of capturing a two-dimensional image comprising the steps of:

collecting light reflected from, transmitted through or emitted by a surface or a medium with the aid of optics, said optics enabling variable focus;

processing said light collected by said optics in an imaging spectrograph comprising at least a grating and mirror configured concentrically and a two-dimensional array of sensor elements that receive a spectral dispersion of said light collected by said optics;

recording spectral distributions of said light collected by said optics at each point along a line through an image of said surface or medium, wherein movement of at least one of at least said array of sensor elements or said surface or medium enables capture of a plurality of ones of said lines;

verifying calibration of said imaging spectrograph with respect to a reference;

controlling said imaging spectrograph with the aid of one or more processors through an interface to an external computer system;

computing, for each said spectral distribution, values of one or more variables that provide a representation of said spectral distribution; and

storing at least said values of said one or more variables in memory of said external computer system along with information having at least a time of capture of said image.

17. The method according to claim 16 wherein said reference for calibration is integrated with said imaging spectrograph, enabling at least estimation of the dark current of the sensor array and verification of wavelength calibration of said spectrograph.

18. The method according to claim 16 wherein said storing step further comprises storing said one or more variables and the time of capture of said image in a database along with information identifying a source of said one or more variables.

19. The method according to claim 16 further comprising the step of comparing values of said one or more variables representative of a point on said image to desired values for a plurality of said points to provide information utilized for quality control.

20. The method according to claim 19 wherein said comparing step further comprises the step of preparing one or more histograms comprising a plurality of said values associated with said one or more variables for comparison to one or more corresponding histograms comprising desired values.

21. The method according to claim 20 further comprising the step of computing differences between said one or more histograms and said one or more corresponding histograms and comparing said differences to an error criterion for the purpose of process control in a production system.

22. The method according to claim 16 wherein at least one of said one or more variables is utilized for rendering a visual representation of said image.

23. The method according to claim 22 further comprising the step of rendering said visual representation of said image responsive to user-modifiable tonal transfer curves for one or more channels of a color rendering device.

24. The method according to claim 16 wherein said step of computing values for each said spectral distribution convolves said spectral distribution with one or more spectral functions corresponding, respectively, with each of said one or more variables.

25. The method according to claim 24 wherein said one or more spectral functions are related to human color sensitivity.

26. The method according to claim 25 further comprising the step of rendering a visual representation of said image with the aid of at least one color profile, said color profile comprising one or more color transformations and fields identifying said one or more color transformations in which said one or more color transformations comprise at least a conversion of said values of said one or more variables into device dependent coordinates for said rendering.

27. The method according to claim 16 further comprising the step of measuring the spectral distribution of light incident upon said surface or medium, said measurement useful for representation of the colors of an image of said surface or medium under different conditions of illumination.

28. A system for capturing a two-dimensional image comprising:

optics for collecting light reflected from, transmitted through or emitted by a surface or a medium, wherein said optics enable variable focus;

an imaging spectrograph for processing said light collected by said optics, said imaging spectrograph comprising at least a grating and a minor configured concentrically and a two-dimensional array of sensor elements that receive a spectral distribution of said light collected by said optics at each point along a line through an image of said surface or medium;

one or more processors for controlling said imaging spectrograph, storing said spectral distributions of said light collected by said optics and communicating with an external computer through an interface, wherein movement of at least one of at least said array of sensor elements or said surface or medium enables capture of a plurality of ones of said lines; and

software executable by one or both of said one or more processors or said external computer comprising;

a program enabling operation of said system from said external computer;

a program for verifying at least the wavelength calibration of said system;

a program for processing said spectral data to produce a spectral distribution of light for each said point along said line through said image;

a program for computing, based upon said spectral distribution for each of said points, values of one or more variables that provide a representation of said spectral distribution, wherein at least one of said one or more variables is useable in rendering a visual representation of said image on a rendering device; and

a program for storing at least said values of said one or more variables in memory of said external system.

29. The system according to claim 28 wherein said one or more variables representative of a point on said image have values comparable to desired values for a plurality of said points to provide information utilized for quality control.

30. The system according to claim 28 further comprising an input that enables measurement of the spectral distribution of light incident upon said surface or medium.