US 5,313,291 A · Method for matching color prints to color images on a monitor screen

Abstract

A color correction method is provided for an electronic printing system that results in a color print that is made as close as possible to what an operator actually observes on a monitor screen (What you see is what you get). The printing system includes a computer, a color printer, and a color monitor. A calibration is automatically performed by the system's computer through the use of calibration software, a series of test patterns stored in the computer memory, a monitor calibrating device, and a scanner equipped with color trichromatic measurement capabilities.

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Claims9

Dependent claims

A method for calibrating a color printing system which includes a color CRT monitor, color printer, and source of digital color signals including the steps of:

storing in a controller memory, a predetermined number of sets of C, M, Y, K print codes, each set associated with a specific color value to be printed,
applying each of said print codes sequentially to the color printer for producing color output prints carrying color patches, each color patch corresponding to a specific C, M, Y, K print code applied to said printer,
measuring each said color patch under a particular set of spectral illumination conditions and establishing tristimulus values Xp, Yp, Zp, for each measured color patch,
correlating each measured Xp, Yp, Zp value with the associated C, M, Y, K print code, and storing each correlation in a memory look up table,
storing in said controller memory, a predetermined number of sets of coded digital signals Bm, Gm, Rm, representative of all possible colors capable of being created on a particular color CRT monitor,
applying said sets of coded digital signals sequentially to an associated electron gun of said color CRT monitor, each coded digital signal set creating a color image with a specific Bm, Gm, Rm gun code value,
measuring each said color image in an environment which closely approximates the actual viewing condition of an operator observing the color image at a specific distance from the monitor, each measurement establishing a set of tristimulus values, Xm, Ym, Zm, and
correlating each measured Xm, Ym, Zm set with the associated Bm, Gm, Rm set, and storing each correlation in said memory look up table.
comparing the color range of the printer to the color range of the monitor and limiting the Xm, Ym, Zm range to the Xp, Yp, Zp range, whereby upon selection by an operator of a print operation to print a specific color image displayed on the monitor, a print code C, M, Y, K is generated which is correlated with the stored monitor gun code that produced that particular color image on the monitor resulting in an output print that has the same tristimulus values as the color image on the screen.

6 more elements

A method for generating a color print having the same tristimulus values as a color image displayed on a color CRT monitor screen including the steps of:

storing in a controller memory, a predetermined number of sets of C, M, Y, K print codes, each set associated with a specific color value to be printed,
applying each of said print codes sequentially to a color printer for producing color output prints carrying color patches, each color patch corresponding to a specific C, M, Y, K print code applied to said printer,
measuring each said color patch under a particular set of spectral illumination conditions and establishing tristimulus values Xp, Yp, Zp, for each measured color patch,
correlating each measured Xp, Yp, Zp value with the associated C, M, Y, K print code, and storing each correlation in a memory look up table,
storing in said controller memory, a predetermined number of sets of coded digital signals Bm, Gm, Rm, representative of all possible colors capable of being created on a particular color CRT monitor,
applying said sets of coded digital signals sequentially to an associated electron gun of said color CRT monitor, each coded digital signal set creating a color image with a specific Bm, Gm, Rm gun code value,
measuring each said color image in an environment which closely approximates the actual viewing condition of an operator observing the color image at a specific distance from the monitor, each measurement establishing a set of tristimulus values, Xm, Ym, Zm, and
correlating each measured Xm, Ym, Zm value with the associated applied Bm, Gm, Rm values, and storing each said correlation in said memory look up table comparing the color range of the printer to the color range of the monitor and limiting the Xm, Ym, Zm range to the Xp, Yp, Zp range,
providing a digital input signal to the monitor representing a color image to be printed,
adjusting the initially observed color image to obtain a desired final color image said final color image having a color range limited to that capable of being reproduced by the printer, and
sending a print code to the printer which is correlated to the stored monitor gun code that produced that particular color image on the screen whereby the color print produced has the same tristimulus values as the color image on the screen.

8 more elements

Dependencies are inferred from the claim text.

Description4,431 words

Summary1,337 words

#The present invention relates to an automatic method of color correction for an electronic printing system and, more particularly, to a method of calibrating a color printer and a color monitor so that the appearance of a color print generated by the electronic color printing system closely approximates the appearance of the color image on the monitor screen at the time of printing.

#Various color correction methods are known in the prior art for matching a scanned color original document to a printed color output. Representative disclosures are found in the following U.S. Pat. Nos.

#4,929,978 (Kanamori et al.) discloses a method wherein a color scanner scans an original color image to obtain successive input color values, each value expressed in tricolor color space. A color correction table memory is responsive to one of the input color values for producing corrected data comprising corresponding output color values. A color printer responsive to the output color values reproduces the original color image as an output color image.

Brief description of the drawings7 figures

#FIG. 1 is a block diagram of the color imaging system of the invention, including a computer, color printer, and color monitor.

#FIG. 2 is a schematic block diagram of the calibration circuit for calibrating the printer of FIG. 1.

#FIG. 3 is a flow chart showing the printer calibration process.

Detailed description2,983 words

#While the invention is described in some detail below with reference to a specific embodiment, it is to be understood that there is no intention to limit it solely to that embodiment. On the contrary, the intent is to cover all modifications, alternatives, and equivalents of the invention, as defined by the appended claims.

#At the outset it will be helpful to briefly define some of the terminology that is used herein.

#As is known, color can be described with three variables. Blue, green, and red light emitted by a CRT monitor, or contained by the light emitted by a source and reflected from an object, determines the characteristic of the light reaching the eyes. This is called the "stimulus". Three variables (B, G, and R) usually are sufficient to define a color stimulus. These values are called tristimulus values or trichromatic values.

Facts

Application

07/797,671Filed 25 Nov 1991

Granted

17 May 1994

Term ended

25 Nov 2011

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification4 codes

H04N 1/6086
Controlled by factors external to the apparatus: by scene illuminant, i.e. conditions at the time of picture capture, e.g. flash, optical filter…
H04N 1/6055
Matching two or more picture signal generators or two or more picture reproducers: using test pattern analysis
H04N 1/6088
Controlled by factors external to the apparatus: by viewing conditions, i.e. conditions at picture output
H04N
Pictorial communication

Method for matching color prints to color images on a monitor screen

Life of this patent

Method for matching color prints to color images on a monitor screen

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims9

Description4,431 words

Drawings

Classification4 codes

Life of this patent

Description4,431 words