System for distributing and controlling color reproduction at multiple sites

• US 20030020703A1
• Filed: 07/31/2002
• Published: 01/30/2003
• Est. Priority Date: 08/25/1997
• Status: Active Grant

• Current Assignee: RAH Color Technologies LLC
• Original Assignee: RAH Color Technologies LLC
• Inventors: Holub, Richard A.
• Granted Patent: US 7,075,643 B2
• Time in Patent Office: Days
• US Class Current: 345/207
• 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 the 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 represent a color display in which a member surrounds the outer periphery of the screen of the display and a color measuring instrument is coupled to the first member. The color measuring instrument includes a sensor spaced from the screen at an angle with respect to the screen for receiving light from an area of the screen. 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 sample to a spectrograph. The color measuring instruments provide for non-contact measurements of color samples either displayed on a color display, or printed on a sheet, and are self-calibrating by the use of calibration references in the instrument.

Claims

1. An assembly for measuring color from a color display having a screen comprising:

a first member surrounding the outer periphery of said display, and

a color measuring instrument coupled to said first member and spaced from said screen at an angle with respect to the screen for receiving light from an area of the screen.

2. The assembly according to claim 1 wherein said first member reduces the amount of ambient light to said screen.

3. The assembly according to claim 1 wherein said first member has an interior which is black in color.

4. The assembly according to claim 1 wherein said color measuring instrument converts said received light into electrical signals representative of said light.

5. The assembly according to claim 1 wherein said color measuring instrument is directed to said screen to minimize the amount of specularly reflected light in said light received by said color measurement instrument.

6. The assembly according to claim 1 wherein said color measurement instrument comprises a sensor and optics for focusing light received from said screen onto said sensor.

7. The assembly according to claim 6 wherein said sensor is a photo-diode array.

8. The assembly according to claim 6 wherein said sensor is a fiber-optic pickup coupled to a spectrograph.

9. The assembly according to claim 1 wherein first member has an exterior and a light source mounted to said exterior.

10. The assembly according to claim 1 further comprising means for mounting said first member to said color display.

11. The assembly according to claim 10 wherein said means comprises a rack and pinion assembly adjustable to the size of the display.

12. The assembly according to claim 1 further comprising a viewing box having a top side which is contiguous with said first member, a back side, and open side opposing said back side, in which media is locatable in the interior of the viewing box.

13. The assembly according to claim 12 wherein said viewing box further comprises at least one light source for illuminating said media.

14. The assembly according to claim 13 wherein said open side has reflectors providing an aperture through which said media is viewable.

15. The assembly according to claim 1 wherein said color measurement instrument comprising:

a housing;

at least one sensor in said housing for converting light received by said sensor from said screen into electrical signals representative of said light;

optics in said housing for focusing light onto said sensor; and

control circuitry for receiving said electrical signals from said sensor and converting said electrical signals into a digital value representative of the light received by said sensor.

16. The assembly according to claim 15 wherein said color measurement instrument further comprises a spectrally selective filter through which said optics focus light from said screen onto said sensor.

17. The assembly according to claim 15 wherein said sensor represents a first sensor and said color measurement instrument has a second sensor for converting light received by said sensor into electrical signals representative of said light, wherein said second sensor is protected from receiving any light, and said control circuity selects electrical signals from one of said first and second sensors.

18. The assembly according to claim 15 wherein said second sensor provides electrical signals representative of the absence of light to account for the effect of temperature on said first sensor.

19. The assembly according to claim 15 wherein said sensor has one or more color channels.

20. The assembly according to claim 1 wherein said first member represents a frame detachable from said display, wherein said frame has a rear edge which rests against the front of said display without obstructing the view of said screen.

21. A system for providing automatic color calibration of a color display having a screen comprising:

a first member surrounding the outer periphery of said display; and

a color measuring instrument coupled to said first member and spaced from said screen at an angle with respect to the screen for receiving light from the screen, wherein said color measurement instrument comprises a housing, at least one sensor in said housing for converting light received by said sensor from said screen into first electrical signals representative of said light, optics in said housing for focusing light onto said sensor; and

control circuitry for receiving said first electrical signals from said sensor and converting said first electrical signals into second electrical signals representative of the color of the light received by said sensor.

22. The system according to claim 21 further comprising a computer coupled to said display for receiving said second electrical signals.

23. The system according to claim 21 wherein said sensor is one of a photo-diode array, and a fiber-optic pickup coupled to a spectrograph.

24. The system according to claim 21 further comprising means for mounting said color measuring instrument to said first member.

25. The system according to claim 21 further comprises a computer coupled to said display for receiving said second electrical signals in which said computer outputs images corresponding to calibration references on said display and said second electrical signals provide calibration data to said computer in accordance with said output images on said display.

26. A method for maintaining calibration of a color display having a screen comprising the steps of:

adjusting the amount of light from the screen when said screen is dark to account for ambient light;

neutral balancing the color of the display;

measuring the gamma in each color channel of the display; and

adjusting the color produced by the display in accordance with the gammas measured in each color channel.

27. The method according to claim 26 wherein said light from said screen is emitted or reflected light.

28. An apparatus for measuring color of a sample comprising:

a dual beam spectrograph having first and second inputs;

a light source;

first means for transmitting light from said light source to illuminate said sample;

second means for transmitting light from said light source to said first input of said spectrograph to provide a reference for calibrating said spectrograph;

third means for receiving light from said sample and transmitting said received light to said second input of said spectrograph for analyzing the spectrum of said received light; and

one or more sensors which also receives light from said first means in which said sensors provide information for checking the calibration of the spectrograph.

29. The apparatus according to claim 28 wherein said first means, second means, and third means each represent at least one fiber optic.

30. An apparatus for measuring the color reflected from a sample comprising:

a light source for illuminating said sample;

a line of light in which at least a part of said light represents light of one or more calibration references, and the remaining part of said line represents light received from said sample; and

a spectrograph which receives said line of light and outputs spectra spatially related to points along said line, in which part of said spectrum is related to said light of said calibration references and provides information for checking the calibration of the spectrograph.

31. The apparatus according to claim 30 wherein said light of said calibration references comprises a first part representing light from said light source, a second part representing light of a dark reference, and a third part representing light of one or more known wavelengths.

32. The apparatus according to claim 30 wherein said line of light is provided by optical means representing one of a fiber optic array, and lens.

33. The apparatus according to claim 32 wherein said optical means and the sample move relative to each other to scan the sample.

34. An apparatus for measuring color rendered by a printer comprising:

means for transporting a sheet rendered from the printer having color samples,

at least one optical sensor coupled to said transporting means which is directed to said sheet to measure the color of the color sample; and

said sensor comprising at least one fiber optic probe and a spectrograph coupled to said fiber optic probe, and said spectrograph comprises means for automatically obtaining references for calibration of the spectrograph.

35. The apparatus according to claim 34 wherein said transporting means enables said sensor and the sample to move relative to each other to scan the sample.

36. The apparatus according to claim 34 further comprising an illuminator for supplying light to said sample.

37. The apparatus according to claim 36 where said illuminator and said sensor are disposed adjacent to the surface of said sample without contacting said sample at about 45 degrees to each other.

38. The apparatus according to claim 36 wherein said illuminator has a first polarizer for polarizing light from said illuminator, and said sensor has a second polarizer which cross polarizes the light received from said sample.

39. A system for controlling color reproduction comprising:

a network having one or more nodes;

one of said nodes having a computer system having a database;

means for communicating between others of said nodes and said one of said nodes; and

said other of said nodes each having at least one rendering device, wherein said database stores data for calibrating the rendering device at each of said nodes.

40. The system according to claim 39 wherein said data represents one or more color profiles.

41. The system according to claim 39 further comprising means for virtual proofing at the rendering device, of said other of said nodes.