Method for measuring color registration and determining registration error in a marking platform

• US 20020113968A1
• Filed: 12/15/2000
• Published: 08/22/2002
• Est. Priority Date: 12/15/2000
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Dirkx, Michael P., Parisi, Michael A.
• Granted Patent: US 6,493,083 B2
• Time in Patent Office: Days
• US Class Current: 356/399
• CPC Class Codes: B41J 29/393 Devices for controlling or analysing the entire machine ; Controlling or analysing mechanical parameters involving printing of test patterns
• CPC Class Codes: G03G 15/0152 onto which the monocolour toner images are superposed before common transfer from the recording member
• CPC Class Codes: G03G 15/0163 primary transfer to the final recording medium
• CPC Class Codes: G03G 2215/00042 Optical detection
• CPC Class Codes: G03G 2215/00063 Colour
• CPC Class Codes: G03G 2215/0161 Generation of registration marks
• CPC Class Codes: H04N 1/506 Reproducing the colour component signals picture-sequentially, e.g. with reproducing heads spaced apart from one another in the subscanning direction

Abstract

An image registration detection system in a multicolor marking platform determines registration of non-black colors using either the reflectance or the density of a test pattern as a measurement parameter. A method is also provided to determine the degree of registration error of each non-black color using the density of the test pattern. The present invention encompasses any marking platform that develops multicolor images in color separation layers that are in superimposed registration with one another, including electrophotographic and ink marking platforms. The apparatus and method disclosed require less measurement precision than prior color registration methods. Registration measurements can be performed on images formed on a photoreceptor, images transferred to an intermediate substrate, images transferred to a target substrate, or images fused to a target substrate. The method disclosed also requires less processing overhead than prior registration methods while providing a more precise method of estimating registration error.

Claims

1. A method of measuring registration in a multicolor marking platform comprising the following steps:

a) marking a first region of a test pattern and a second region of a test pattern on an image receiving member using a black marking material representing a black color separation and a non-black color marking material representing a non-black color separation;

b) illuminating the first region with a light source and detecting the reflected light rays;

c) illuminating the second region with the light source and detecting the reflected light rays; and

,

d) determining the registration between the non-black color separation and the black color separation by comparing the light rays reflected by the first region to the light rays reflected by the second region.

2. The method of measuring registration in a multicolor marking platform as set forth in claim 1, wherein step d) further includes the following steps:

e) converting the detected light rays from the first region to a first signal indicative of the reflectance of the first region;

f) converting the detected light rays from the second region to a second signal indicative of the reflectance of the first region; and

g) determining whether or not the non-black color separation and black color separation are in proper registration with each other by comparing the first signal and second signal to each other.

3. The method of measuring registration in a multicolor marking platform as set forth in claim 2, further comprising the following step:

h) estimating an amount of registration error when the non-black color separation and black color separation are not in proper registration with each other.

4. The method of measuring registration in a multicolor marking platform as set forth in claim 3, wherein step h) further includes the following step:

i) estimating the amount of registration error according to the equation x=(2a (R<sub>avg, x>

0</sub>−

R_{avg, x=0}))/(1−

R_{avg, x=0})², wherein;

a is the width of a black bar in the first region and second region;

R<sub>avg, x>

0</sub> is a value representing the reflectance of the first region;

R_{avg, x=0} is a value representing the reflectance of the second region; and

,

x is the estimated registration error.

5. The method of measuring registration in a multicolor marking platform as set forth in claim 1, wherein step d) further includes the following steps:

e) converting the detected light rays from the first region to a first signal indicative of the density of the first region;

f) converting the detected light rays from the second region to a second signal indicative of the density of the first region; and

g) determining whether the non-black color separation and the black color separation are in proper registration with each other by comparing the first signal and second signal to each other.

6. The method of measuring registration in a multicolor marking platform as set forth in claim 5, further comprising the following step:

h) estimating an amount of registration error when the non-black color separation is not in proper registration with the black color separation.

7. The method of measuring registration in a multicolor marking platform as set forth in claim 6, wherein step h) further includes the following step:

i) estimating the amount of registration error according to the equation x=(2a (10<sup>−

De</sup>−

10<sup>−

Dr</sup>))/(1−

10<sup>−

Dr</sup>)², wherein;

a is the width of a black bar in the first region and second region;

De is a value representing the density of the first region;

Dr is a value representing the density of the second region; and

,

x is the estimated registration error.

8. The method of measuring registration in a multicolor marking platform as set forth in claim 1, wherein step a) further includes the following steps:

e) marking a third region and a fourth region of the test pattern on the image receiving member using the black marking material and the non-black color marking material; and

,

further comprising the following steps;

f) illuminating the third region with the light source and detecting the reflected light rays;

g) illuminating the fourth region with the light source and detecting the reflected light rays; and

,

h) determining the registration between the non-black color separation and the black color separation in a direction perpendicular to that determined in step d) by comparing the light rays reflected by the third region to the light rays reflected by the fourth region.

9. The method of measuring registration in a multicolor marking platform as set forth in claim 8, wherein step a) and step e) further includes the following steps for marking each region of the test pattern:

i) marking a plurality of parallel black bars and a plurality of parallel non-black color bars in separate steps but in any order, wherein;

each black bar is of about equal width and about equally spaced from each other;

the spacing between each black bar is about equal to the width of each black bar;

each non-black color bar is of about equal width and equally spaced from each other;

the width of the non-black color bar is about 1.5 times the width of the black bar;

the spacing between each non-black color bar is about 0.5 times the width of the black bar; and

,

the plurality of parallel black bars and the plurality of parallel non-black color bars are positioned such that the right edge of the right most non-black color bar mates with the left edge of the right most black bar.

10. The method of measuring registration in a multicolor marking platform as set forth in claim 9, wherein step a) further includes the following step:

j) marking the second region at about a 180 degree rotation in reference to the first region; and

,

wherein step e) further includes the following steps;

k) marking the third region at about a 90 degree rotation in reference to the first region; and

,

l) marking the fourth region at about a 270 degree rotation in reference to the first region.

11. The method of measuring registration in a multicolor marking platform as set forth in claim 8, wherein the light source used in steps b), c), f), and g) illuminates the region with light rays that are a complementary color to the non-black color separation.

12. The method of measuring registration in a multicolor marking platform as set forth in claim 8, wherein the detecting in steps b), c), f), and g) is accomplished by a sensor with a filter that is a complementary color to the non-black color separation.

14. The method of measuring registration in a multicolor marking platform as set forth in claim 13, wherein step c) further includes the following steps:

d) converting the detected light rays from the first region to a signal indicative of the reflectance of the first region; and

,

e) determining whether the non-black color separation and the black color separation are in proper registration with each other by comparing the signal and the first stored known reference value, wherein the first stored known reference value represents a condition when the non-black color separation and the black color separation are in proper registration with each other.

15. The method of measuring registration in a multicolor marking platform as set forth in claim 14, further comprising the following step:

f) estimating an amount of registration error when the non-black color separation and black color separation are not in proper registration with each other.

16. The method of measuring registration in a multicolor marking platform as set forth in claim 15, wherein step f) further includes the following step:

g) estimating the amount of registration error according to the equation x=(2a (R<sub>avg, x>

0</sub>−

R_{avg, x=0}))/(1−

R_{avg, x=0})², wherein;

a is the width of a black bar in the first region and second region;

R<sub>avg, x>

0</sub> is a value representing the reflectance of the first region;

R_{avg, x=0} is the first stored known reference value; and

,

x is the estimated registration error.

17. The method of measuring registration in a multicolor marking platform as set forth in claim 13, wherein step c) further includes the following steps:

d) converting the detected light rays from the first region to a signal indicative of the density of the first region; and

,

e) determining whether the non-black color separation and the black color separation are in proper registration with each other by comparing the signal and the first stored known reference value, wherein the first stored known reference value represents a condition when the non-black color separation and the black color separation are in proper registration with each other.

18. The method of measuring registration in a multicolor marking platform as set forth in claim 17, further comprising the following step:

f) estimating an amount of registration error when the non-black color separation is not in proper registration with the black color separation.

19. The method of measuring registration in a multicolor marking platform as set forth in claim 18, wherein step f) further includes the following step:

g) estimating the amount of registration error according to the equation x=(2a (10<sup>−

De</sup>−

10<sup>−

Dr</sup>))/(1−

10<sup>−

Dr</sup>)², wherein;

a is the width of a black bar in the first region and second region;

De is a value representing the density of the first region;

Dr is the first stored known reference value; and

,

x is the estimated registration error.

20. The method of measuring registration in a multicolor marking platform as set forth in claim 13, wherein step a) further includes the following steps:

d) marking a second region, a third region, and a fourth region of the test pattern on the image receiving member using the black marking material and the non-black color marking material; and

,

further comprising the following steps;

e) illuminating the second region with the light source and detecting the reflected light rays;

f) determining the registration between the non-black color separation and the black color separation in a direction opposite to that determined in step c) by comparing the light rays reflected by the second region to a second stored known reference value;

g) illuminating the third region with the light source and detecting the reflected light rays;

h) determining the registration between the non-black color separation and the black color separation in a direction perpendicular to that determined in step c) by comparing the light rays reflected by the third region to a third stored known reference value;

i) illuminating the fourth region with the light source and detecting the reflected light rays; and

,

j) determining the registration between the non-black color separation and the black color separation in a direction opposite to that determined in step h) by comparing the light rays reflected by the second region to a second stored known reference value.

21. The method of measuring registration in a multicolor marking platform as set forth in claim 20, wherein step a) and step d) further includes the following steps for marking each region of the test pattern:

k) marking a plurality of parallel black bars and a plurality of parallel non-black color bars in separate steps but in any order, wherein;

each black bar is of about equal width and about equally spaced from each other;

the spacing between each black bar is about equal to the width of each black bar;

each non-black color bar is of about equal width and equally spaced from each other;

the width of the non-black color bar is about 1.5 times the width of the black bar;

the spacing between each non-black color bar is about 0.5 times the width of the black bar; and

,

the plurality of parallel black bars and the plurality of parallel non-black color bars are positioned such that the right edge of the right most non-black color bar mates with the left edge of the right most black bar.

22. The method of measuring registration in a multicolor marking platform as set forth in claim 21, wherein step d) further includes the following steps:

l) marking the second region at about a 180 degree rotation in reference to the first region;

m) marking the third region at about a 90 degree rotation in reference to the first region; and

,

n) marking the fourth region at about a 270 degree rotation in reference to the first region.

23. The method of measuring registration in a multicolor marking platform as set forth in claim 20, wherein the light source used in steps b), e), g), and i) illuminates the region with light rays that are a complementary color to the non-black color separation.

24. The method of measuring registration in a multicolor marking platform as set forth in claim 20, wherein detecting in steps b), e), g), and i) is accomplished by a sensor with a filter that is a complementary color to the non-black color separation.

26. The image registration detection system as set forth in claim 25, wherein the controller is for determining the registration of the two color separations to each other from the measurement performed by the sensor.

27. The image registration detection system as set forth in claim 25, wherein the sensor is for measuring the reflectance of any one of the plurality of test patterns.

28. The image registration detection system as set forth in claim 25, wherein the sensor is for measuring the density of any one of the plurality of test patterns.

29. The image registration detection system as set forth in claim 25, wherein the image receiving member is a transferred target substrate.

13. A method of measuring registration in a multicolor marking platform comprising the following steps:

a) marking a first region of a test pattern on an image receiving member using a black marking material representing a black color separation and a non-black color marking material representing a non-black color separation;

b) illuminating the first region with a light source and detecting the reflected light rays; and

,

c) determining the registration between the non-black color separation and the black color separation by comparing the light rays reflected by the first region to a first stored known reference value.

25. An image registration detection system in a multicolor marking platform comprising:

an image marking member for marking a plurality of marking materials, each marking material representing a different color separation;

an image receiving member for receiving a plurality of marking materials;

a controller for controlling the marking of a plurality of test patterns on the image receiving member, each test pattern including two marking materials disposed to indicate a registration relative to the different color separations; and

,

a sensor for measuring the light rays reflected by any one of the plurality of test patterns at an angle to a light source illuminating said test pattern.

30. An image registration detection system in an electrophotographic multicolor marking platform comprising:

a controller for controlling the mar king of a plurality of test patterns on an image receiving member, each test pattern including two marking materials disposed to indicate a registration relative to the different color separations;

a marking engine for mar king a plurality of marking materials, each marking material representing a different color separation;

an image receiving member for receiving a plurality of marking materials; and

,

a sensor for measuring the light rays reflected by any one of the plurality of test patterns at an angle to a light source illuminating said test pattern.

31. The image registration detection system as set forth in claim 30, wherein the image receiving member is a fused target substrate in a xerographic environment.