Systems and methods for sensing marking substrate area coverage using a spectrophotometer

• US 7,110,142 B2
• Filed: 11/02/2001
• Issued: 09/19/2006
• Est. Priority Date: 11/02/2001
• Status: Expired due to Fees

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Mestha, Lalit K., Saber, Eli S.
• Primary Examiner(s): Zimmerman, Mark
• Assistant Examiner(s): Rohwer, Jacob P.
• Application Number:
  US09/985,419
• Publication Number:
  US 20030086103A1
• Time in Patent Office: 1,782 Days
• Field of Search: 358/1.9, 358/1.4, 358/504, 358/509, 358/518
• US Class Current: 358/1.9
• CPC Class Codes: G03G 2215/00042 Optical detection
• CPC Class Codes: H04N 1/6033 using test pattern analysis H04N1/6055 takes precedence

Abstract

A multiple-LED sensor is used to detect area coverage of marked patches on a marking substrate. The same sensor may also be used for color calibration. The marking substrate area coverage sensor obtains reflectance measurements from marked patches of a marking substrate. For example, the marked patches may be patches of a marking substance such as toner, ink or paint, or patches marked by etching or the like. A Neugebauer model may be used to obtain the reflectance measurements. A batch least squares algorithm may be used to estimate the appropriate parameters of the Neugebauer model. For improved accuracy, a recursive least squares algorithm may be used. The recursive least squares algorithm allows the marking substrate area coverage sensor to calibrate itself to changes in the sensing environment.

Claims

1. A method of obtaining marking substrate area coverage information, comprising:

obtaining a base reflectance of an unmarked portion of a marking substrate;

obtaining a reference reflectance of a reference marked patch of the marking substrate at substantially complete coverage;

obtaining a target reflectance of a target marked patch of the marking substrate; and

obtaining an estimated marking substrate area coverage ĉ

of the target marked patch by a least squares algorithm, based on the base reflectance, the reference reflectance and the target reflectance, using a Neugebauer model of the form

y=Ac

where

2. The method of claim 1, wherein the marked patch comprises a marking substance.

3. The method of claim 2, wherein the marking substance is one of ink, toner and paint.

4. The method of claim 1, wherein the least squares algorithm minimizes the square of errors between the reference reflectance and the target reflectance.

5. A computer-readable storage medium on which is recorded a program for implementing the method of claim 1.

6. A marking system parameter control system, comprising a controller that:

obtains a base reflectance of an unmarked portion of a marking substrate using information output by the sensor;

obtains a reference reflectance of a reference marked patch of the marking substrate at substantially complete coverage;

obtains a target reflectance of a target marked patch of the marking substrate; and

obtains an estimated marking substrate area coverage ĉ

of the target marked patch by a least squares algorithm, based on the base reflectance, the reference reflectance and the target reflectance, using a Neugebauer model of the form

y=Ac

where

7. A method of obtaining marking substrate area coverage information, comprising:

obtaining a base reflectance of an unmarked portion of a marking substrate;

obtaining a reference reflectance of a reference marked patch of the marking substrate at substantially complete coverage;

obtaining an initial estimated marking substrate area coverage ĉ

of a target marked patch of the marking substrate;

obtaining a target reflectance of the target marked patch;

obtaining a first improved estimated marking substrate area coverage ĉ

by an adaptive equation, based on the initial estimated marking substrate area coverage ĉ

, the base reflectance, the reference reflectance and the target reflectance using a Neugebauer model of the form

y=Ac

where

8. The method of claim 7, further comprising:

repeating the obtaining a target reflectance of the target marked patch; and

repeating the obtaining a second improved estimated marking substrate area coverage ĉ

, using the first improved estimated marking substrate area coverage ĉ

as the initial estimated marking substrate area coverage ĉ

, the second improved estimated marking substrate area coverage ĉ

being closer than the first improved estimated marking substrate area coverage ĉ

to actual marking substrate area coverage c.

9. The method of claim 7, wherein the marked patch comprises a marking substance.

10. The method of claim 9, wherein the marking substance is one of ink, toner and paint.

11. The method of claim 7, wherein the obtaining the initial estimated marking substrate area coverage ĉ

comprises using a Neugebauer model of the form

y=Ac

where

12. A computer-readable storage medium on which is recorded a program for implementing the method of claim 7.

13. A marking system parameter control system, comprising a controller that:

obtains a base reflectance of an unmarked portion of a marking substrate;

obtains a reference reflectance of a reference marked patch of the marking substrate at substantially complete coverage;

obtains an initial estimated marking substrate area coverage ĉ

of a target marked patch of the marking substrate;

obtains a target reflectance of a target marked patch;

obtains a first improved estimated marking substrate area coverage ĉ

by an adaptive equation, based on the initial estimated marking substrate area coverage ĉ

, the base reflectance, the reference reflectance and the target reflectance using a Neugebauer model of the form

y=Ac

where