US4464045A
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US
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Method of and an arrangement for calibrating a color copying apparatus
Assignee: Agfa Gevaert AG
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Filing: 1982-06-07
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Granted: 1984-08-07
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Expires: 2002-06-07
Abstract
Abstract A color copying apparatus having a photoelectric color exposure control device is calibrated by making a copy of a calibrating original, which includes a gray stepped wedge, on a photographic copying material using an exposure determined by the photoelectric color exposure control device and assumed to be proper for achieving the desired density values in the developed image of the calibrating original. The density of the developed image of the gray stepped wedge is then measured in order to obtain actual density values, which are compared with corresponding desired density values. Finally, the photoelectric color exposure control device is adjusted for achieving the required exposure correction as determined during the comparison of the actual and desired values. The calibration is performed for each of the individual values so that correction of the control device is also achieved for each of the corresponding colors.
Inventors
- 👤 Gunter Findeis
- 👤 Berthold Fergg
- 👤 Wolfgang Zahn
- 👤 Gerhard Kuhn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 18:34
CPC Classifications
G; G03; G03B; G03B27/00; G03B27/72; G03B27/73
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
332 words
A method of calibrating a color copying apparatus, comprising the steps of copying a calibrating original which includes a stepped gray zone having steps of predetermined density and color composition onto a copying material; processing the copying material to obtain a developed image of the calibrating original; measuring the densities of the calibrating original and the developed image thereof in each of the three primary colors; and adjusting the exposure using the equations Δ(log I·t).sub.B =Δ.sub.B +α.sub.GB Δ.sub.G +α.sub.RB Δ.sub.R Δ(log I·t).sub.G =α.sub.BG Δhd B+Δ.sub.G +α.sub.RG Δ.sub.R Δ(log I·t).sub.R =α.sub.BR Δ.sub.B +α.sub.GR Δ.sub.G +Δ.sub.R where I is the light intensity during exposure, t is the exposure time, the subscripts B, G and R, respectively, denote blue, green and red, the α coefficients have absolute values smaller than one and depend upon the characteristics of the copying material, and the Δ coefficients on the right-hand sides of the equations are defined by the expressions ##EQU5## b m and b u being the blue densities of respective steps on the calibrating original, g m and g v being the green densities of respective steps on the calibrating original, r m and r w being the red densities of respective steps on the calibrating original, B m and B u being the blue densities of the developed images of respective steps on the copying material, G m and G v being the green densities of the developed images of respective steps on the copying material, R m and R w being the red densities of the developed images of respective steps on the copying material, B z being the desired blue density of a predetermined field of the developed image of the stepped zone on the copying material, G z being the desired green density of a predetermined field of the developed image of the stepped zone on the copying material, and R z being the desired red density of a predetermined field of the developed image of the stepped zone on the copying material.
Claim 2
Independent Claim
332 words
A method of calibrating a color copying apparatus, comprising the steps of copying a calibrating original which includes a stepped gray zone having steps of predetermined density and color composition onto a copying material; processing the copying material to obtain a developed image of the calibrating original; measuring the densities of the calibrating original and the developed image thereof in each of the three primary colors; and adjusting the exposure using the equations Δ(log I·t).sub.B =Δ.sub.B +α.sub.GB Δ.sub.G +α.sub.RB Δ.sub.R Δ(log I·t).sub.G =α.sub.BG Δhd B+Δ.sub.G +α.sub.RG Δ.sub.R Δ(log I·t).sub.R =α.sub.BR Δ.sub.B +α.sub.GR Δ.sub.G +Δ.sub.R where I is the light intensity during exposure, t is the exposure time, the subscripts B, G and R, respectively, denote blue, green and red, the α coefficients have absolute values smaller than one and depend upon the characteristics of the copying material, and the Δ coefficients on the right-hand sides of the equations are defined by the expressions ##EQU5## b m and b u being the blue densities of respective steps on the calibrating original, g m and g v being the green densities of respective steps on the calibrating original, r m and r w being the red densities of respective steps on the calibrating original, B m and B u being the blue densities of the developed images of respective steps on the copying material, G m and G v being the green densities of the developed images of respective steps on the copying material, R m and R w being the red densities of the developed images of respective steps on the copying material, B z being the desired blue density of a predetermined field of the developed image of the stepped zone on the copying material, G z being the desired green density of a predetermined field of the developed image of the stepped zone on the copying material, and R z being the desired red density of a predetermined field of the developed image of the stepped zone on the copying material.
Claim 3
Dependent Claim
47 words
The method as defined in claim 1, wherein the calibrating original includes markings respectively aligned with the steps and operative for scanning control, and areas outside of the stepped zone having such density and color composition that the calibrating original in its entirety has a middle density.
Claim 4
Dependent Claim
89 words
The method as defined in claim 1; and further comprising the steps of making another copy of the calibrating original on the copying material using exposure differing by a predetermined percentage from that used during the copying step; determining the characteristic curves of the copying material, by evaluating only that region of each of the copies which corresponds to a region of the calibrating original having an approximately known density; and approximating the characteristic curves, based on parameters derived from the evaluated regions of the copies, by mathematical functions.
Claim 5
Dependent Claim
38 words
The method as defined in claim 3, wherein said approximating step includes respectively utilizing a normal distribution curve, and a straight line for the mathematical function in the curved and substantially straight regions of the respective characteristic curve.
Claim 6
Dependent Claim
31 words
The method as defined in claim 1, wherein said copying step is performed using an empirical exposure assumed to be correct for achieving the desired density values in the developed image.
Claim 7
Dependent Claim
14 words
The method as defined in claim 5, wherein the empirical exposure is determined photoelectrically.
Claim 8
Dependent Claim
16 words
The method as defined in claim 1, wherein the color copying apparatus is a photographic apparatus.
Claim 9
Dependent Claim
20 words
The method as defined in claim 1, wherein said adjusting step is performed in automatic response to said measuring step.
Claim 10
Dependent Claim
23 words
The method as defined in claim 8, wherein the calibrating original has markings aligned with the respective steps and operative for scanning control.
Claim 11
Dependent Claim
25 words
The method as defined in claim 1, wherein the individual color exposures do not substantially influence one another and the α coefficients are substantially zero.
Claim 12
Dependent Claim
9 words
The method as defined in claim 10, wherein ##EQU6##
Claim 13
Dependent Claim
39 words
The method as defined in claim 1, wherein B z , G z and R z are the respective blue, green and red densities of a central field of the image of the stepped zone on the copying material.
Claim 14
Dependent Claim
33 words
The method as defined in claim 1, wherein the subscripts m and u represent adjacent steps, the subscripts m and v represent adjacent steps and the subscripts m and w represent adjacent steps.
Claim 15
Dependent Claim
51 words
The method as defined in claim 1, wherein u=m-1 when (B z -B m )<0, u=m+1 when (B z -B m )>0, v=m-1 when (G z -G m )<0, v=m+1 when (G z -G m )>0, w=m-1 when (R z -R m )<0, and w=m+1 when (R z -R m )<0.
Claim 16
Dependent Claim
334 words
An arrangement for calibrating a color copying apparatus having an exposure control device, comprising measuring means for measuring the densities of the respective steps of a stepped gray zone on a calibrating original in each of the three primary colors and for measuring the densities of the respective developed images of the steps on copying material in each of the three primary colors; and adjusting means for adjusting the exposure control device using the equations Δ(log I·t).sub.B =Δ.sub.B +α.sub.GB +Δ.sub.G +α.sub.RB Δ.sub.R Δ(log I·t).sub.G =α.sub.BG Δ.sub.B +Δ.sub.G +α.sub.RG Δ.sub.R Δ(log I·t).sub.R =α.sub.BR Δ.sub.B +α.sub.GR Δ.sub.G +Δ.sub.R where I is the light intensity during exposure, t is the exposure time, the subscripts B, G and R respectively denote blue, green and red, the α coefficients have absolute values smaller than one and depend upon the characteristics of the copying material, and the Δ coefficients on the right-hand sides of the equations are defined by the expressions ##EQU7## b m and b u being the blue densities of respective steps on the calibrating original, g m and g v being the green densities of respective steps on the calibrating original, r m and r w being the red densities of respective steps on the calibrating original, B m and B u being the blue densities of the developed images of respective steps on the copying material, G m and G v being the green densities of the developed images of respective steps on the copying material, R m and R w being the red densities of the developed images of respective steps on the copying material, B z being the desired blue density of a predetermined field of the developed image of the stepped zone on the copying material, G z being the desired green density of a predetermined field of the developed image of the stepped zone on the copying material, and R z being the desired red density of a predetermined field of the developed image of the stepped zone on the copying material.
Claim 17
Dependent Claim
334 words
An arrangement for calibrating a color copying apparatus having an exposure control device, comprising measuring means for measuring the densities of the respective steps of a stepped gray zone on a calibrating original in each of the three primary colors and for measuring the densities of the respective developed images of the steps on copying material in each of the three primary colors; and adjusting means for adjusting the exposure control device using the equations Δ(log I·t).sub.B =Δ.sub.B +α.sub.GB +Δ.sub.G +α.sub.RB Δ.sub.R Δ(log I·t).sub.G =α.sub.BG Δ.sub.B +Δ.sub.G +α.sub.RG Δ.sub.R Δ(log I·t).sub.R =α.sub.BR Δ.sub.B +α.sub.GR Δ.sub.G +Δ.sub.R where I is the light intensity during exposure, t is the exposure time, the subscripts B, G and R respectively denote blue, green and red, the α coefficients have absolute values smaller than one and depend upon the characteristics of the copying material, and the Δ coefficients on the right-hand sides of the equations are defined by the expressions ##EQU7## b m and b u being the blue densities of respective steps on the calibrating original, g m and g v being the green densities of respective steps on the calibrating original, r m and r w being the red densities of respective steps on the calibrating original, B m and B u being the blue densities of the developed images of respective steps on the copying material, G m and G v being the green densities of the developed images of respective steps on the copying material, R m and R w being the red densities of the developed images of respective steps on the copying material, B z being the desired blue density of a predetermined field of the developed image of the stepped zone on the copying material, G z being the desired green density of a predetermined field of the developed image of the stepped zone on the copying material, and R z being the desired red density of a predetermined field of the developed image of the stepped zone on the copying material.
Claim 18
Dependent Claim
48 words
The arrangement as defined in claim 15, wherein said adjusting means includes a computer connected to said measuring means at its input means and to the exposure control device at its output means and operative for calculating the exposure correction and for adjusting the exposure control device accordingly.
Claim 19
Dependent Claim
62 words
The arrangement as defined in claim 16, wherein said measuring means includes a first densitometer for measuring the densities of the stepped zone on the calibrating original and a second densitometer for measuring the densities of the image of the stepped zone on the copying material said first and second densitometers being connected to first and second inputs of said computer, respectively.
Claim 20
Dependent Claim
25 words
The arrangement as defined in claim 17; and further comprising a signal storage interposed between said first densitometer and said first input of said computer.
Claim 21
Dependent Claim
22 words
The arrangement as defined in claim 17, wherein said first densitometer is constituted by a scanning arrangement of the exposure control device.
Claim 22
Dependent Claim
16 words
The arrangement as defined in claim 15, wherein the color copying apparatus is a photographic apparatus.
Claim 23
Dependent Claim
25 words
The arrangement as defined in claim 15, wherein the individual color exposures do not substantially influence one another and the α coefficients are substantially zero.
Claim 24
Dependent Claim
9 words
The arrangement as defined in claim 21, wherein ##EQU8##
Claim 25
Dependent Claim
39 words
The arrangement as defined in claim 15, wherein B z , G z and R z are the respective blue, green and red densities of a central field of the image of the stepped zone on the copying material.
Claim 26
Dependent Claim
33 words
The arrangement as defined in claim 15, wherein the subscripts m and u represent adjacent steps, the subscripts m and v represent adjacent steps and the subscripts m and w represent adjacent steps.
Claim 27
Dependent Claim
51 words
The arrangement as defined in claim 15, wherein u=m-1 when (B z -B m )<0, u=m+1 when (B z -B m )>0, v=m-1 when (G z -G m )<0, v=m+1 when (G z -G m )>0, w=m-1 when (R z -R m )<0, and w=m+1 when (R z -R m )>0.
Claim 28
Dependent Claim
34 words
The arrangement as defined in claim 15, wherein said adjusting means is arranged to adjust the exposure control device in automatic response to a predetermined difference between an actual and a desired density value.
Claim 29
Dependent Claim
15 words
The arrangement as defined in claim 15, wherein said exposure control device comprises photoelectric means.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-08-07 | 1988-02-06 | 1988-08-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-08-07 | 1992-02-06 | 1992-08-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-08-07 | 1996-02-06 | 1996-08-07 | $7700.00 | Window Closed / Lapsed |