Method for determining a sheet height

Patent metadata

Field	Value
Publication number	US-9600748-B2
Application number	US-201514954414-A
Country	US
Kind code	B2
Filing date	Nov 30, 2015
Priority date	Dec 1, 2014
Publication date	Mar 21, 2017
Grant date	Mar 21, 2017

Abstract

A method is provided for determining a sheet height of a sheet conveyed by a sheet transportation unit. An optical sensor is used for sensing the surface geometry of the sheet, resulting in a two-dimensional height image of the sheet. The height image has pixels that have a value representing a local height of the sheet. The method comprises the steps of: a) selecting from the height image pixels that have a deviating value; b) substituting the deviating value of a selected pixel by a realistic value that is derived from not selected pixels; and c) determining a sheet height by finding a maximum value from the values of the not selected pixels and the substituted values. Furthermore, a print system is provided that comprises a control unit that is configured to apply the invented method.

First claim

What is claimed is:

1. A method for selecting a sheet for transportation along a print process unit by determining a sheet height of a sheet, the method comprising:
conveying the sheet by a sheet transportation unit;
sensing the surface geometry of the sheet, during the conveying, using an optical sensor, resulting in a two-dimensional height image of the sheet, the height image having pixels that have a value representing a local height of the sheet; and
using a data processor to:
select a pixel from the height image that has a deviating value in comparison to its direct environment;
substitute the deviating value of the selected pixel by a realistic value that is derived from not selected pixels;
determine a sheet height by finding a maximum value from the values of the not selected pixels and the substituted values; and
eliminate a sheet if the sheet height is larger than a predetermined threshold.

2. The method according to claim 1 , wherein a pixel is selected for having a deviating value if a first difference between the pixel value and a nearest neighbour pixel value exceeds a predetermined threshold.

3. The method according to claim 2 , wherein a pixel is selected for having a deviating value if a difference between the pixel and a further nearest neighbour also exceeds a predetermined threshold and is opposite to the first difference.

4. The method according to claim 1 , wherein the realistic value is derived from the nearest neighbour values by selecting one of the nearest neighbour values.

5. The method according to claim 1 , wherein the realistic value is derived from the nearest neighbour values by extrapolating a number of values of pixels in a line pointing to the selected pixel.

6. The method according to claim 1 , wherein a light beam is applied perpendicular to a sheet surface and the optical sensor is directed in a direction opposite to a transport direction of the sheet.

7. A printing system, comprising:
a sheet transportation unit for conveying a sheet to a print process unit;
an optical sensor for sensing a surface geometry to determine a two-dimensional height image of the sheet; and
a data processor configured to determine a sheet height from the two-dimensional height image of the sheet by:
selecting from the height image a pixel that has a deviating value;
substituting the deviating value of the selected pixel by a realistic value that is derived from not selected pixels;
determining a sheet height by finding a maximum value from the values of the not selected pixels and the substituted values; and
eliminating a sheet if the sheet height is larger than a predetermined threshold.

8. A printing system according to claim 7 , wherein a sheet expelling unit is comprised that expels a sheet from the transportation unit before the sheet arrives at the print process unit if the determined sheet height exceeds a predetermined threshold.

Assignees

• Océ-Technologies B V

Inventors

• Van Acquoij Catharinus
• Kawaguchi Daisuke
• Janssen Cornelius M F

Classifications

• H04N1/00745

  Detecting the leading or trailing ends of a moving sheet · CPC title

• H04N1/00734

  Optical detectors · CPC title

• H04N1/00716 Primary

  Thickness · CPC title

• G01B11/0608

  Height gauges · CPC title

• B41J11/0095

  Detecting means for copy material, e.g. for detecting or sensing presence of copy material or its leading or trailing end · CPC title