Color calibration of color image rendering devices

• US 10,038,884 B2
• Filed: 02/12/2018
• Issued: 07/31/2018
• Est. Priority Date: 08/31/2005
• Status: Expired due to Fees

• Current Assignee: RAH Color Technologies LLC
• Original Assignee: RAH Color Technologies LLC
• Inventors: Holub, Richard A.
• Primary Examiner(s): Nguyen, Hau H
• Application Number:
  US15/894,545
• Publication Number:
  US 20180176529A1
• Time in Patent Office: 169 Days
• CPC Class Codes: G01J 2003/2866 Markers; Calibrating of scan
• CPC Class Codes: G01J 2003/466 Coded colour; Recognition of predetermined colour; Determining proximity to predetermined colour
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0202 Mechanical elements; Supports for optical elements
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/0262 Constructional arrangements for removing stray light
• CPC Class Codes: G01J 3/0264 Electrical interface; User interface
• CPC Class Codes: G01J 3/0272 Handheld
• CPC Class Codes: G01J 3/0289 Field-of-view determination; Aiming or pointing of a spectrometer; Adjusting alignment; Encoding angular position; Size of measurement area; Position tracking
• CPC Class Codes: G01J 3/0291 Housings; Spectrometer accessories; Spatial arrangement of elements, e.g. folded path arrangements
• CPC Class Codes: G01J 3/18 using diffraction elements, e.g. grating gratings per se G02B
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• 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 3/50 using electric radiation detectors
• CPC Class Codes: G01J 3/506 measuring the colour produced by screens, monitors, displays or CRTs
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G03B 27/547 colour mixing heads
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 2207/20072 Graph-based image processing
• CPC Class Codes: G06T 7/80 : Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
• CPC Class Codes: G06T 7/90 : Determination of colour characteristics
• CPC Class Codes: G09G 2320/0285 : using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0626 : for control of overall brightness
• 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 2330/021 : Power management, e.g. power saving
• CPC Class Codes: G09G 2360/144 : the light being ambient light
• CPC Class Codes: G09G 2360/147 : the originated light output being determined for each pixel
• CPC Class Codes: G09G 3/3413 : Details of control of colour illumination sources
• 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 1/6033 : using test pattern analysis H04N1/6055 takes precedence
• CPC Class Codes: H04N 1/6052 : Matching two or more picture signal generators or two or more picture reproducers
• CPC Class Codes: H04N 17/02 : for colour television signals
• CPC Class Codes: H04N 17/045 : Self-contained testing apparatus
• CPC Class Codes: H04N 23/13 : with multiple sensors
• CPC Class Codes: H04N 23/88 : for colour balance, e.g. white-balance circuits or colour temperature control
• CPC Class Codes: H04N 9/12 : Picture reproducers H04N9/11 takes precedence
• CPC Class Codes: H04N 9/3182 : Colour adjustment, e.g. white balance, shading or gamut white balance per se H04N9/73; control of amplitude of colour signals H04N9/68; colour control circuits for displays in general G09G5/02, G09G3/2003, G09G3/3607
• CPC Class Codes: H04N 9/3194 : including sensor feedback
• CPC Class Codes: H04N 9/68 : for controlling the amplitude of colour signals, e.g. automatic chroma control circuits H04N9/71, H04N9/73 take precedence; camera processing pipelines for controlling the colour saturation of colour signals H04N23/86
• CPC Class Codes: H04N 9/73 : Colour balance circuits, e.g. white balance circuits or colour temperature control camera processing pipelines for colour balance H04N23/88

Abstract

Color calibration of color image rendering devices, such as large color displays, which operate by either projection or emission of images, utilize internal color measurement instrument or external color measurement modules locatable on a wall or speaker. A dual use camera is provided for a portable or laptop computer, or a cellular phone, handset, personal digital assistant or other handheld device with a digital camera, in which one of the camera or a display is movable with respect to the other to enable the camera in a first mode to capture images of the display for enabling calibration of the display, and in a second mode for capturing image other than of the display. The displays may represent rendering devices for enabling virtual proofing in a network, or may be part of stand-alone systems and apparatuses for color calibration. Improved calibration is also provided for sensing and correcting for non-uniformities of rendering devices, such as color displays, printer, presses, or other color image rendering device.

Claims

1. A system of color management at nodes of a network comprising:

a plurality of presses, each at a different one of said nodes of the network, each of said presses provide color image reproductions on media using at least three colorants, and is associated with a controller that processes calibration data for the press, wherein said controller has a network interface, and said media is of physical material;

each of said presses having at least one imaging sensor positioned with respect to said media moving through the press to provide measurements of said color image reproductions printed upon said media by the press, and a source of illumination reflecting from or passing through said media for detection by said imaging sensor, wherein said imaging sensor comprises a plurality of channels having spectral response functions;

at least one video monitor displaying menus to an operator that enable control of color reproduction, and information indicative of color reproduction performance, for one or more of said presses;

a computer comprising one or more processors that connects to the network and receives data comprising numerical results representative of said color reproduction performance from the controller associated with each of said one or more of said presses, wherein at least one of said one or more processors has access to a database storing said received data; and

one or more programs executable by one of said computer and the controller associated with each of said presses, said one or more programs comprising;

a program that uses the spectral response functions of said imaging sensor for one of said presses and the spectral transmission or reflection functions of the colorants applied to said media by said one of said presses to compute at least one of amounts of the colorants or the spectral distribution of combinations of the colorants present in one of said color reproductions printed on said media by said one of said presses;

a program that computes color values of said one of said color reproductions in device independent units;

a program that computes differences between said color values based on measurements by said imaging sensor of colors printed by said one of said presses and reference color values; and

a program providing correction of at least neutral balance of said one of said presses to reduce said differences between said color values based on said measurements by said imaging sensor of colors printed by said one of said presses and said reference color values, wherein said correction for said differences between color values depends partly on interactions between the colorants that vary with spatial position on said media.

2. The system according to claim 1 wherein said controller associated with said one of said presses modifies color reproduction by said one of said presses responsive to said differences between said color values based on said measurements by said imaging sensor of colors printed by said one of said presses and said reference color values in accordance with a criterion for color error.

3. The system according to claim 2 wherein said computer assists said controller associated with said one of said presses by storing said reference color values and computing modifications to values of variables that control color reproduction by said one of said presses in accordance with a model of the relationship between said variables and color rendered by said one of said presses.

4. The system according to claim 2 wherein said computer further provides a criterion for matching color reproduction between said one of said presses and at least another one of said presses.

5. The system according to claim 2 wherein said nodes represent first nodes and said computer further communicates with one or more second nodes along said network to send said information related to performance of said presses at said first nodes.

6. The system according to claim 1 wherein said program that computes said differences employs histograms in computing said differences, wherein said histograms are corrected for said differences that are due to spatial position on said media for said one of said presses.

7. The system according to claim 1 wherein said nodes represent first nodes along said network, said system comprises one or more second nodes along said network, and said video monitor is present at one of said first and second nodes for displaying said computed differences.

8. The system according to claim 1 wherein said at least one video monitor displays images of color reproduction by said one of said presses.

9. The system according to claim 1 wherein said at least one video monitor displays images computed from said measurements of said color reproductions by the sensor for each of said presses.

10. The system according to claim 1 wherein said at least one video monitor is calibrated to a colorimetric standard to provide visual representation of color reproduction by said one of said presses.

11. The system according to claim 1 wherein the controller at one or more of said nodes is provided by said computer linked to said video monitor for displaying the menus that enable control of color reproduction and said information indicative of color reproduction performance of at least the press associated with the controller.

12. The system according to claim 1 wherein said one of said one or more processors having access to said database further stores said received data along with time of measurement by said imaging sensor for each of the presses.

13. The system according to claim 12 wherein said access to said database is provided by a server along said network.

14. A method for managing color at nodes of a network comprising:

rendering image reproductions on media by a plurality of presses using at least three colorants, in which each of said presses is at a different one of said nodes of the network, and said media is of physical material;

processing calibration data by a controller for each of said presses in which said controller has a network interface;

positioning for each of said presses at least one imaging sensor with respect to said media moving through the press to provide measurements of said color image reproductions printed upon said media by the press, and a source of illumination reflecting from or passing through said media for detection by said imaging sensor, in which said imaging sensor has a plurality of channels having spectral response functions;

displaying menus on at least one video monitor to an operator that enable control of color reproduction, and information indicative of color reproduction performance, for one or more of said presses;

connecting to the network a computer having one or more processors that receives data comprising numerical results representative of said color reproduction performance from the controller associated with each of said one or more said presses;

accessing by at least one of said one or more processors a database storing said received data; and

executing one or more programs by one of said computer and the controller associated with each of said presses, providing the steps of;

computing at least one of amounts of the colorants or the spectral distribution of combinations of the colorants present in one of said color reproductions printed on said media by one of said presses using the spectral response functions of said imaging sensor for said one of said presses and the spectral transmission or reflection functions of the colorants applied to said media by said one of said presses;

computing color values of said one of said color reproductions in device independent units;

computing differences between said color values based on measurements by said imaging sensor of colors printed by said one of said presses and reference color values; and

correcting at least neutral balance of said one of said presses to reduce said differences between said color values based on said measurements by said imaging sensor of colors printed by said one of said presses and said reference color values, wherein said step of correcting said differences depends partly on interactions between the colorants that vary with spatial position on said media.

15. The method according to claim 14 further comprising the step of modifying, by said controller associated with said one of said presses, color reproduction by said one of said presses responsive to said differences between said color values based on said measurements by said imaging sensor of colors printed by said one of said presses and said reference color values in accordance with a criterion for color error.

16. The method according to claim 15 further comprising the step of utilizing said computer to assist said controller associated with said one of said presses by storing said reference color values and computing modifications to values of variables that control color reproduction by said one of said presses in accordance with a model of the relationship between said variables and color rendered by said one of said presses.

17. The method according to claim 15 further comprising the step of utilizing a criterion for matching color reproduction between said one of said presses and at least another one of said presses.

18. The method according to claim 15 wherein said nodes represent first nodes and said computer communicates with one or more second nodes along said network to send information related to performance of said presses at said first nodes.

19. The method according to claim 14 wherein said computing differences step utilizes histograms in computing said differences, and said method further comprises the step of correcting said histograms for differences that are due to spatial position on said media for said one of said presses.

20. The method according to claim 14 further comprising the steps of:

calibrating said at least one video monitor to a colorimetric standard; and

displaying a visual representation of color reproduction by said one of said presses.

21. The method according to claim 14 further comprising the steps of:

computing images from said measurements of said color reproductions by the imaging sensor for each of said presses; and

displaying said images on said at least one video monitor.

22. The method according to claim 14 wherein said displaying step is carried out by the controller at one of more of said nodes associated with the presses using said video monitor for displaying the menus that enable control of color reproduction and said information indicative of color reproduction performance for at least the press associated with the controller.

23. The method according to claim 14 wherein said at least one of said one or more processors carrying out said accessing step further provides storing said received data along with time of measurement by said imaging sensor for each of the presses.