System for automatic color calibration

• US 6,459,425 B1
• Filed: 08/25/1998
• Issued: 10/01/2002
• Est. Priority Date: 08/25/1997
• Status: Expired due to Term

• Current Assignee: RAH Color Technologies LLC, Richard A. Holub
• Original Assignee: Richard A. Holub
• Inventors: Holub, Richard A., Mongeau, Daniel R.
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): Tran, Henry N.
• Application Number:
  US09/139,498
• Time in Patent Office: 1,498 Days
• Field of Search: 345/150, 345/151, 345/207, 345/22, 345/204, 345/593, 345/594, 345/690, 348/243, 348/253, 348/254, 348/259, 348/267, 348/335, 348/602, 348/804, 348/794, 348/180, 348/336, 348/778, 348/789, 348/824, 348/827, 348/832, 348/834, 348/842, 348/843, 422/167
• 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

A system for automatic color calibration for a color display is provided having an assembly of a member adjacent the outer periphery of the screen of the display and a color measuring instrument coupled to the member. The system is particularly usefull at a site or node of a network of sites or nodes for distributing and controlling color reproduction. 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. Methods are also provided for maintaining calibration of a color display using a color measuring instrument. Apparatuses are further provided for checking the calibration of a color measurement instrument having a spectrograph for measuring color.

Claims

1. An assembly for non-contact measurement of color from a color display having a screen comprising:

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

a color measuring instrument coupled to said first member non-contact with said screen, wherein said color measuring instrument has at least one lens and is positioned for receiving light from an area of the screen through said lens.

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 having two racks coupled for movement by a pinion.

12. 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.

13. The assembly according to claim 12 wherein said color measurement instrument further comprises a spectrally selective filter through which said optics focus light from said screen onto said sensor.

14. The assembly according to claim 12 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.

15. The assembly according to claim 12 wherein said second sensor provides electrical signals representative of the absence of light to account for the effect of temperature on said first sensor.

16. The assembly according to claim 12 wherein said sensor has one or more color channels.

17. 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.

18. The assembly according to claim 1 wherein said color measurement instrument is positioned at an angle with respect to the screen.

19. The assembly according to claim 1 wherein said color measurement instrument is positioned to provide an unobstructive view of said screen.

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

a first member surrounding the outer periphery of said display;

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

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 niedia is locatable in the interior of the viewing box.

21. The assembly according to claim 20 wherein said viewing box further comprises at least one light source for illuminating said media.

22. The assembly according to claim 21 wherein said open side has reflectors providing an aperture through which said media is viewable.

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

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

a color measuring instrument coupled to said first member and non-contact with said screen and positioned for receiving light from said 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.

24. The system according to claim 23 further comprising a computer coupled to said display for receiving said second electrical signals.

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

26. The system according to claim 23 further comprising means for mounting said color measuring instrument to said first member.

27. The system according to claim 23 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.

28. The assembly according to claim 23 wherein said color measurement instrument is positioned at an angle with respect to the screen.

29. The assembly according to claim 23 wherein said color measurement instrument is positioned to provide an unobstructive view of said screen.

30. 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 gamnma in each color channel of the display wit the aid of a sensor directed in a non-contact relationship to said screen; and

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

31. The method according to claim 30 wherein said light from said screen is emitted or reflected light.

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

a first member adjacent the outer periphery of said display;

a color measuring instrument coupled to said first member for receiving light from the screen; and

a viewing box contiguous with said first member in which media is locatable in the interior of the viewing box.