WO1994001755A1 - Method and calibration device for calibrating computer monitors used in the printing and textile industries - Google Patents
Method and calibration device for calibrating computer monitors used in the printing and textile industries Download PDFInfo
- Publication number
- WO1994001755A1 WO1994001755A1 PCT/US1993/005699 US9305699W WO9401755A1 WO 1994001755 A1 WO1994001755 A1 WO 1994001755A1 US 9305699 W US9305699 W US 9305699W WO 9401755 A1 WO9401755 A1 WO 9401755A1
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- Prior art keywords
- monitor
- brightness
- monitors
- color
- white point
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/46—Colour picture communication systems
- H04N1/56—Processing of colour picture signals
- H04N1/60—Colour correction or control
- H04N1/603—Colour correction or control controlled by characteristics of the picture signal generator or the picture reproducer
- H04N1/6052—Matching two or more picture signal generators or two or more picture reproducers
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N17/00—Diagnosis, testing or measuring for television systems or their details
- H04N17/02—Diagnosis, testing or measuring for television systems or their details for colour television signals
Definitions
- This invention relates to a method and device for calibrating color and monochrome monitors to the reflected color temperature of various papers used in printing, textile and allied processes and user defined calibrations.
- the papers, textiles of fabric being illuminated by American National Standards Institute PH2.30 transmissive color temperature of 5,000 degrees Kelvin and 7,500 degrees Kelvin specified by the American Society for Testing Materials ASTM D1684-61.
- the device also defines the brightness and contrast settings of the monitors, as well as defining the brightness setting of the monitor to compensate for brightness of ambient light.
- an image can be viewed as it will be printed. That through the process herein described, monitors of various manufacture and locations can be calibrated to the same standard, that an image viewed on various monitors so calibrated will look the same.
- Color and monochrome monitors used with computers in the production of prepress material for color printing are manufactured by various processes. Therefore, an image will look different in brightness, contrast and color when viewed on various monitors on which it is displayed.
- calibrators have created calibrators to define standard white point ' color temperature settings on color monitors and to permit the user to select an arbitrary brightness and contrast settings.
- the white point color temperature settings defined by these devices when displayed on various color monitors are not the same color temperature when viewed.
- Using such calibration devices to set specific white point setting on monitors of various manufacturing process will show an image to be different in color, brightness and contrast.
- Various patents and available devices disclosed devices and methods to calibrate monitors.
- Calibrators as the Radius Precision Color Calibrator, SuperMatch Calibrator, RasterOps Calibrator, MonCal calibrator, by Radius, Inc., 1710 Fortune Dr., San Jose, CA 94063, SuperMac Technology, 485 Potero Ave., Sunnyvale, CA 94086, RasterOPs, 2500 Walsh Ave., Santa Clara, CA 95051 and Sequel Imaging, 1 Palm Drive, Londonderry, NH 03053, provides the means to maintain a monitor calibration to specific white point color temperature settings.
- the SuperMatch Calibrator provides user defined white point gamma color temperature control albeit the monitor cannot be automatically calibrated to such settings.
- the monitors calibration described it this prior art assumes a 5,000 degree Kelvin white point color temperature displayed on a monitor [TV], to be a simulation of white paper reflection 5,000 degrees Kelvin light, stating that both peak white point [TV] and illumination must be of a suitable color temperature, with the example of 5.000K being given.
- white papers have various color reflection indexes, reflected light from the paper will not be 5,000 degrees Kelvin, therefore with the monitor set to 5.000K this white point will not match the light reflected from the paper.
- this prior art does not stipulate that the monitor should be 5.000K. With this parameter being applied then the monitor image cannot be accurately compared to the printed image as the white point color temperature of the monitor is not that of 5.000K lights reflected from the white paper.
- monitors used in this process are not accurately calibrated, and do not display the image as it will print.
- the calibration devices disclosed are also not designed to define and set monitor brightness and contrast or relate the monitor brightness to the brightness of ambient light.
- monitor calibration device and system particularly for color and monochrome monitors used in the printing and textile industries, where accurate reproduction is required.
- the system should be able to calibrate all such monitors used in these industries that the image will appear the same whatever the location or manufacturing process that produced the monitors. Assuming the same color temperature ambient light and the software application set to the same parameters on a computer that the monitor is being used to display the image.
- this objective can be achieved by defining white point color temperatures of light transmitted from standard light sources of a color matching light booth reflected from papers used in printing processes. That these settings and user defined alternatives can be transferred to color monitors via a device calibrated to such settings, by which monitors can be electronically or optically compared to the device and calibrated. Also with this device, monitors can be calibrated for brightness and contrast through reading standard white point and black point references that the monitor can be adjusted to. The monitors can be calibrated for variations in brightness of the ambient lighting. Thus, monitors produced by various manufacturing processes and at various locations, can be calibrated to the same standard. That images prepared for prepress color and monochrome reproduction can be viewed identically and as they will be printed with the software applications. being identically calibrated on the computer.
- [c] to provide a method to transfer the white point color temperature settings of [b] to a color monitor by adjusting the monitors white point color temperature, that light so transmitted to an opal screen, being the lower half of the screen described in [b], matches standard of [b];
- the invention is used to adjust color monitors to specific requirements of the prepress textile and printing industries. Therefore, it is assumed software applications are being used that TIFF files can be loaded on the computer and displayed on the monitor.
- a TIFF file [A] consisting of white and gray calibration targets is loaded on the computer and displayed on the monitor.
- the calibration device placed in front of the monitor displays on Liquid Crystal Displays, density readings of the plaques read with photoelectric cells.
- the Brightness, and where provided, Contrast controls of the monitor are adjusted that the readings of the calibration targets are those of the pre ⁇ defined settings for brightness and contrast.
- the device is calibrated for monitors without a contrast control.
- a filter holder with filter set for specific white point for a given paper or textile is inserted in the slot provided, and the light so filtered is displayed on the top half of an opal display.
- the white point gamma control software GAMMA by KNOLL or similar software, or red, green, blue gamma control of a monitor is used to adjust the monitor white point color temperature.
- Three photoelectric cells receiving signals of red, green, blue wavelengths of light via filters from the lower half of an opal screen of the device, are indicated on a Liquid Crystal Display, adjustments are made to the white point color temperature of the monitor.
- the invention is used to adjust color monitors to specific requirements of the prepress textile and printing industries. Therefore, it is assumed software applications are being used that TIFF files can be loaded on the computer and displayed on the monitor.
- a TIFF file [A] consisting of white and gray calibration targets is loaded on the computer and displayed on the monitor.
- the calibration device placed in front of the monitor indicates on Liquid Crystal Displays, density readings of the plaques read with photoelectric cells.
- the Brightness, and where provided, Contrast controls of the monitor are adjusted that the readings of the calibration targets are those of the pre ⁇ defined settings for brightness and contrast.
- the device is calibrated for monitors without a contrast control.
- a filter holder with filter set for specific white point for a given paper or textile is inserted in the slot provided, and the light so filtered is displayed on the top half of an opal display.
- the white point gamma control software GAMMA by KNOLL or similar software, or red, green, blue gamma control of a monitor is used to adjust the monitor white point color temperature displayed on the lower half of an opal screen of the device. The adjustments are compared to the required white point color temperature of [3] displayed on the top half of an opal screen.
- the TIFF file target [A] is displayed on the monitor and Liquid Crystal Display [B] is directed via a switch to indicate the ambient light through a photoelectric cell located at the top of the device.
- the invention is used to adjust monochrome monitors to the specific requirements of the prepress industry. Therefore it is assumed software applications are being used that TIFF files can be loaded on the computer and displayed on the monitor.
- a TIFF file [A] consisting of white and gray calibration targets is loaded on to the computer and displayed on the monitor.
- the calibration device placed in front of the monitor indicates on Liquid Crystal Displays, density readings of the plaques read with photoelectric cells.
- the Brightness, and where provided, Contrast controls of the monitor are adjusted that the readings of the calibration targets are those of the pre ⁇ defined settings for brightness and contrast.
- the device is calibrated for monitors without a contrast control.
- the Liquid Crystal Display [B] is directed via a switch to read the ambient light through a photoelectric cell located at the top of the device.
- the monitor brightness indicated on Liquid Crystal Display [A] is adjusted to that of the ambient light intensity indicated on Liquid Crystal Display [B].
- FIG. 1 shows a front general perspective view of the embodiment of the calibration device.
- FIG.2 shows a rear general perspective view of the embodiment of the calibration device.
- FIG. 3 shows a front cutaway general perspective view of the embodiment of the calibration device.
- FIG. 4 shows a rear cutaway general perspective view of the embodiment of the calibration device.
- FIGS. 5 and 6 shows a general graphical view of the method by which the calibration device is calibrated.
- FIG. 7 shows a general graphical view of the calibration device as it is used to calibrate a color monitor.
- FIG. 8 shows a schematic of the electronic circuit
- FIG. 9 shows a schematic of the lamp circuit
- FIG. 10a shows the response of the photoelectric cells
- FIG. 11a shows Spectrophotometric curves of Wratten filters 47,58,25.
- Fig. 12a shows ambient light adjustment chart
- Fig. 13 shows light box calibrator
- a plug 18 is shown to permit connection of device to electric supply, that with switch 16, the lamp 36 [Figs 3-4] via transformer and starter 38 [Figs 3, 9] is turned on, together with electronic components.
- a light box [Fig 13] transmitting diffused 20 foot candles of light is used to calibrate the meters of the device.
- switch 14 [Figs 1-2]
- photoelectric cells 44,46,48 [Figs 1, 2, 8, 10a] are selected.
- the meters 10,11,12, [Figs 1, 2, 8] display readings of the activated photoelectric cells 44,46,48 [Figs 4, 8, 10a] that have Kodak Wratten color separation filters in front of them [Fig 11a].
- the potentiometers on circuit board 40 [Fig 3] for meters 10, 11, 12 [Figs 1-2] are adjusted to read 200.
- Photocells 29 and 31 [Fig 2] are selected via switch 14 [Figs 1-2]. If the readings displayed on meters 11 and 12 [Figs 1-2] are not those as predetermined, then neutral density filters of increased density value are used to achieve the required readings.
- Switch 14 [Figs 1-2] is used to select ambient light sensing photocell 22 and monitor brightness photocell 29 together with meters 11 and 12 [Fig 1-2].
- the ambient photocell 22 [Figs 1,2,4] is calibrated using neutral density filters, that reading 30 foot candles of ambient light and displayed on meter 12 [Figs 1-2], the reading equals that of meter 11 displaying the 20 foot candles transmitted light of the light box [Fig 13].
- Light from the lamp 36 [Figs 3-4] is transmitted through selected combinations of cyan, magenta, yellow, red, green, blue color compensating filters 34 [Figs 3-5], with wave length of 400-700mu and percent transmission 0.025-0.10 and neutral filters with transmission densities 0-1.3.
- light transmitted through the opal screen of the calibration device simulates the color temperature of -13-
- the filter pack combination 34 [Figs 3-6] required to calibrate the devise 68 [Figs 5-6] to that of the reflected light from the paper or textile. That with a 18 percent reflectance neutral gray card 70 [Fig 6] as specified above, is placed over the the opal screen 24 [Fig 6], that through a window in the card 72 [Fig 6] the standard observer 66 [Fig 6] can determine that the light from the lamp 36 [Figs 3-4] of the calibration device 68 [Fig 6], transmitted through a filter pack 34 [Figs 5-6], retained in a filter holder 20 [Figs 5-6] and placed in the filter slot 90 [Fig 5] of the calibration device 68 [Fig 5], matches the color and percent reflectance of the printing paper or textile 60 [Figs 5-6].
- the neutral density filters of the filter pack 34 [Fig 5] are then adjusted to increase or decrease the density of the pack that the transmitted light displayed on the opal screen 24 [Figs 5-6] of the calibration device is that as determined from measuring in foot candles the brightness of the opal screen of the device with the filter pack 34 in the filter holder 20 within the filter slot 90 of the device 68 [Figs 5,7], the monitor white point brightness standard determined correct for a printing or textile reproduction process transmitted from the monitor 65 [Fig 7] to the opal screen 24 [Figs 1 ,3,4,5,6]. This is achieved with the device correctly located in front of the monitor as described below.
- the calibration device 68 [Fig 7] being placed in front of a monitor Fig 7.
- the monitor is tilted to an angle that the brightness and contrast controls of the monitor are accessible.
- the calibration device is moved toward the monitor that the rubber eye caps 86 [Fig 2] of the brightness and contrast sensing photoelectric cells 31 [Fig 2] are in contact with the monitor and prevent ambient light entering the photocells.
- a software application e.g., Adobe PhotoShop 2.0 or above
- a TIFF file Brightness/Contrast plaque is opened and displayed on the monitor.
- the image filling the screen of the monitor 65 [Fig 7] is divided into three parts, the top half of the screen having the equivalent of 100 percent black, the lower left the equivalent of a 0 percent dot and the lower right the equivalent of 70 percent dot.
- meters 11 , 12, and brightness and contrast photocells 29,31 [Figs 1-2] are selected and the monitor brightness and contrast controls adjusted to predetermined settings displayed on meters 11, 12 [Figs 1-2].
- a White Point TIFF file consisting of a 0 dot percent is opened to fill the screen of the monitor 65 [Fig 7].
- a visual comparison is made of the white point color temperature standard displayed on the top portion of the calibration device screen to that of the monitor white point color temperature displayed on the lower half of the calibration device screen 24 [Figs 1, 5]. If the monitor white point does not match the standard, the monitor gamma and white point adjustment software e.g., GAMMA by KNOLL is selected and displayed on the top left corner of the monitors screen 65 [Fig 7].
- the Red, Green, Blue controls are adjusted to achieve a visual match of the screen white point to that of the standard displayed on the screen of the calibration device 24 [Figs 1, 5].
- Selecting the Red, Green, Blue Photocells 44,46,48 [Fig 4] with switch 14 [Fig 1] the white point readings of the monitor, read with photocells 44, 46, 48 and displayed on meters 10,11 ,12 [Figs 1,4] are compared to that of the required white point color temperature standard. Adjustments to achieve this standard are made with the Red, Green, Blue controls of the gamma and white point adjustment software previously used for the course white point adjustment.
- photocell 22 [Figs 1-4] is selected with switch 14 [Figs 1-2] to measure the brightness of ambient light, also changing meter 12 to display the readings of this photocell.
- the meter reading from photocell 22 is compared to that of the monitor brightness meter readings of photocell 29 [Fig 2]. If the ambient light is greater or less than that specified by the Illuminating Engineering Society for Visual Display Terminals, being 30 foot candles, then the monitor brightness can be adjusted that the meter readings of photocell 29 [Fig 2] taken from the monitor white point as brightness reading, are compared to that ambient light compensation chart Fig 12a.
- the chart having been produced with empirical data, that printed matter being illuminated at levels of foot candle greater and lesser than the ideal 30 foot candles, to be compared to that of the original digital data displayed on the monitor.
- the monitor being adjusted to match the printed copy at the various levels of transmitted illumination.
- the monitor settings and ambient light levels so defined produce the chart from which the monitor brightness level can be set to compensate for any deviation from the 30 foot candles ambient light standard.
- monitor brightness and contrast settings for newsprint reproduction the device can be calibrated to. That with these settings the device is used to calibrate color monitors to the same standard.
- the monitor gamma is set to 1.8 using a gamma control software device e.g., PhotoShop Gamma.
- a foot candles meter the white point is set to 18 foot candles and and the black point to 4 foot candles reading an area equivalent to 70 tone displayed on the monitor. Adjustments to the brightness and contrast controls are made to achieve these settings.
- the ambient light in which the monitor should be viewed is 30 foot candles as required by the Illuminating Engineering Society of North America for Visual Display Terminals.
Abstract
Description
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Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US90910992A | 1992-07-02 | 1992-07-02 | |
US07/909,109 | 1992-07-02 |
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WO1994001755A9 WO1994001755A9 (en) | 1994-02-17 |
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PCT/US1993/005699 WO1994001755A1 (en) | 1992-07-02 | 1993-06-15 | Method and calibration device for calibrating computer monitors used in the printing and textile industries |
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1996000435A1 (en) * | 1994-06-27 | 1996-01-04 | Radius Inc. | Method and apparatus for display calibration and control |
EP1049045A1 (en) * | 1999-03-31 | 2000-11-02 | MadeToOrder.com | Image enhancement for rasterized images |
CN109520928A (en) * | 2018-11-01 | 2019-03-26 | 佛山市同晓科技有限公司 | A kind of glass blocks levelling device |
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Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
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WO1996000435A1 (en) * | 1994-06-27 | 1996-01-04 | Radius Inc. | Method and apparatus for display calibration and control |
US5499040A (en) * | 1994-06-27 | 1996-03-12 | Radius Inc. | Method and apparatus for display calibration and control |
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EP1049045A1 (en) * | 1999-03-31 | 2000-11-02 | MadeToOrder.com | Image enhancement for rasterized images |
CN109520928A (en) * | 2018-11-01 | 2019-03-26 | 佛山市同晓科技有限公司 | A kind of glass blocks levelling device |
CN109520928B (en) * | 2018-11-01 | 2021-05-18 | 佛山市威旭玻璃有限公司 | Glass block leveling device |
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