Device for alignment of images in a control system for a printing press

• US 5,816,151 A
• Filed: 08/14/1997
• Issued: 10/06/1998
• Est. Priority Date: 09/29/1995
• Status: Expired due to Term

• Current Assignee: Shanghai Electric (Group) Corporation (City of Shanghai)
• Original Assignee: Goss Graphic Systems Inc (Manroland GOSS Web Systems International LLC)
• Inventors: Nemeth, Robert, Wang, Xin Xin
• Primary Examiner(s): FISHER, J REED
• Application Number:
  US08/911,214
• Time in Patent Office: 418 Days
• Field of Search: 101/365, 101/181, 101/484, 101/485, 101/DIG. 45, 101/190, 101/171, 101/174, 364/552, 364/528, 364/469.03, 382/162, 382/164, 382/165, 382/181, 382/294, 382/312, 356/429, 356/394, 356/430, 250/559.39, 250/559.04, 250/559.05, 250/559.08, 250/559.07, 250/559.44, 250/559.4, 250/559.2
• US Class Current: 101/171
• CPC Class Codes: B41F 33/0036 Devices for scanning or checking the printed matter for quality control

Abstract

A device for alignment of images for a control system of a printing press having a device for creating targets, a device for aligning a camera, a device for finding actual dot positions on at least one of the targets, a device for calculating the desired dot positions, a device for generating transfer functions, and a device for aligning the images.

Claims

1. A device for alignment of images for a control system of a printing press, comprising:

a black/white camera having a field of view;

a color camera having a plurality of channels and a field of view;

means for printing a pair of targets using an ink containing carbon black, with one of the printed targets having a grid pattern, and the other of the targets having an array of evenly spaced dots forming columns and rows;

means for placing the target having a grid pattern under the camera field of view;

means for displaying an image from the black/white camera and one channel of the color camera;

means for adjusting the cameras to substantially align the two images;

means for placing the dot pattern target under the camera field of view, and capturing images from the black/white camera and a single channel of the color camera;

means for locating the actual X and Y position of each dot in each of the two images;

means for calculating the average X position of each column and Y position of each row of dots, and determining the average spacing between columns and rows and the center point of the dot pattern;

means for calculating a desired column and row spacing, and grid coordinates using the desired column and row spacing;

means for adjusting the grid coordinates such that the center point of the grid is at the center point of the dot pattern;

means for developing transfer functions which map the actual dot positions in that image to the desired dot positions; and

means for capturing an image with the cameras, and performing a geometric transfer operation for each of the four images.

2. The device of claim 1 wherein the calculating means for the desired column and row spacing comprises the desired column and row spacing equal the average column and row spacing such that there is no aspect ratio modification of the captured images.

3. The device of claim 1 wherein the calculating means for the desired column and row spacing comprises either the desired column or row spacing equals the averaged column or row spacing found from the captured images.

4. A device for aligning images developed by first and second cameras in a control system for a printing press using a printed target having a plurality of indicia arranged thereon, comprising:

means for displaying first and second images of the target developed by the first and second cameras, respectively;

means for adjusting a position of at least one of the cameras relative to the other camera based upon the first and second images;

means for finding actual positions of indicia in the first and second images;

means for determining desired positions of indicia in the first and second images;

means for developing at least one transfer function from the actual and desired positions of indicia; and

means for aligning further images developed by the first and second cameras based upon the at least one transfer function.

5. A method of aligning images in a press control system, the method comprising the steps of:

providing first and second cameras;

providing a target having a plurality of indicia arranged thereon;

operating the cameras to capture first and second images of the target;

finding actual positions of indicia in the first and second images;

determining desired positions of indicia in the first and second images;

developing a transfer function from the actual and desired positions of indicia; and

aligning subsequent images developed by the first and second cameras based upon the transfer function.

6. The method of claim 5, wherein one of the cameras has a zoom lens and including the further steps of providing a further target having a grid pattern thereon, viewing the further target through the cameras to obtain a pair of images of the further target and adjusting the zoom lens and moving the at least one camera to bring the pair of images toward alignment.