Device for automatically aligning a production copy image with a reference copy image in a printing press control system

• US 5,812,705 A
• Filed: 06/02/1997
• Issued: 09/22/1998
• Est. Priority Date: 02/28/1995
• Status: Expired due to Term

• Current Assignee: Shanghai Electric (Group) Corporation (City of Shanghai)
• Original Assignee: GOSS Graphic Systems(China) Company Limited (City of Shanghai)
• Inventors: Wang, Xinxin, Nemeth, Robert
• Primary Examiner(s): Mancuso, Joseph
• Assistant Examiner(s): Patel, Jayanti K.
• Application Number:
  US08/867,278
• Time in Patent Office: 477 Days
• Field of Search: 382/162, 382/291, 382/302, 101/115, 355/88
• US Class Current: 382/294
• CPC Class Codes: B41F 33/0036 Devices for scanning or checking the printed matter for quality control
• CPC Class Codes: G06T 2207/10048 Infrared image
• CPC Class Codes: G06T 2207/30144 Printing quality
• CPC Class Codes: G06T 7/001 using an image reference approach
• CPC Class Codes: G06T 7/30 Determination of transform parameters for the alignment of images, i.e. image registration

Abstract

A device to align images for a printing press control system comprising, a device for capturing a reference image containing one or more image planes from a reference copy, a device for converting the reference image into a monochrome reference image, a device for capturing a production image containing one or more image planes from a production copy, a device for converting the production image into a monochrome production image, a device for defining at least one object model in the monochrome reference image, a device for identifying the position of at least one of the object models in the production image, a device for defining a transfer function which maps the position of the models in said monochrome production image to the position of the models in said monochrome reference image, and a device for applying the transfer function to each of the image planes of the production image, resulting in its alignment to the reference image.

Claims

1. A device to align a production image with a reference image in a printing press control system, comprising:

means for capturing at least two monocolor image planes of a color reference image from a reference copy;

means for converting the at least two monocolor image planes of the color reference image into a monochrome reference image;

means for capturing at least two monocolor image planes of a color production image from a production copy;

means for converting the at least two monocolor image planes of the color production image into a monochrome production image;

means for defining at least one object model in the monochrome reference image, the defining means noting a position of the at least one object model;

means for identifying a position of the at least one object model in the monochrome production image;

means for defining a positional transfer function which maps the position of the at least one object model in said monochrome production image to the position of the at least one object model in said monochrome reference image; and

means for applying the positional transfer function to each of the at least two monocolor image planes of the production image to align the production image with the reference image.

2. The device of claim 1 wherein the capturing means captures an infrared image.

3. The device of claim 1 including means for performing an image warp to correct any geometric distortion caused by a lens.

4. The device of claim 1 including means for limiting a maximum displacement between the production and reference copy images.

5. The device of claim 1 including means for dividing the images into four quads.

6. The device of claim 1 wherein the at least one object model comprises four models, and the defining means defines one model in each quad of the monochrome reference image.

7. The device of claim 1 including means for defining a search region for the at least one model, means for searching for the at least one model within the search region to find the position of the at least one model in the monochrome production image, and means for providing the at least one model with a score indicating the degree of match.

8. The device of claim 1 wherein the converting means averages pixel values for the at least two monocolor image planes.

9. The device of claim 1 including means for defining search regions for the at least one model.

10. The device of claim 1 wherein the positional transfer function performs a translation, rotation, scaling or warping function, or any combination of these functions.

11. The device of claim 1 wherein the defining means notes horizontal and vertical coordinates of a center of the at least one object model.

12. A method for obtaining color consistency in a color printing press comprising the steps of:

providing a reference copy of an image;

measuring red, green, and blue reflection values of pixels in the reference copy;

storing the red, green, and blue reflection values measured from the reference copy as numeric values respectively indicating the red, green, and blue content of the pixels in the reference copy of the image;

averaging the numeric values representative of the red, green, and blue content of each pixel in the reference copy of the image to develop a monochrome reference image thereof;

defining at least one model within the monochrome reference image and noting its position in the monochrome reference image;

providing a production copy of the image as printed by the printing press;

measuring red, green, and blue reflection values of pixels in the production copy;

storing the red, green, and blue reflection values measured from the production copy as numeric values respectively indicating the red, green, and blue content of the pixels in the production copy of the image;

averaging the numeric values representative of the red, green, and blue content of each pixel in the production copy of the image to develop a monochrome production image thereof;

searching the monochrome production image for the at least one model and, upon finding the at least one model, noting its position in the monochrome production image;

defining a positional transfer function mapping the position of the at least one model found in the monochrome production image to the position of the at least one model defined in the monochrome reference image;

employing the positional transfer function to align the production copy with the reference copy; and

adjusting the printing press to correct differences between the red, green, and blue reflection values of corresponding pixels in the reference and production copies.

13. A method as defined in claim 12 further comprising the steps of measuring infrared reflection values from the reference copy;

and measuring infrared reflection values from the production copy.

14. A method as defined in claim 13 wherein numeric values representative of the infrared reflection values measured from the reference copy are averaged with the numeric values representative of the red, green, and blue content of each pixel in the reference copy to develop the monochrome reference image.

15. A method as defined in claim 14 wherein numeric values representative of the infrared reflection values measured from the production copy are averaged with the numeric values representative of the red, green, and blue content of each pixel in the production copy to develop the monochrome reference image.

16. A method as defined in claim 13 further comprising the step of adjusting the printing press to correct differences between the infrared reflection values of corresponding pixels in the reference and production copies.

17. A method as defined in claim 12 further comprising the step of correcting the stored numeric values representative of the reflection values measured from the reference copy to correct for distortions in a device used to measure the reflection values.

18. A method as defined in claim 12 further comprising the step of correcting the stored numeric values representative of the reflection values measured from the production copy to correct for distortions in a device used to measure the reflection values.

19. A method as defined in claim 12 further comprising the step of dividing the monochrome reference image into at least two sections.

20. A method as defined in claim 19 wherein the at least one model comprises multiple models, and one of the multiple models is located in each of the at least two sections.

21. A method as defined in claim 12 wherein the positional transfer function performs a translation, a rotation, a scaling, a warping, or any combination of these functions.