Machine vision method and system for the inspection of a material

• US 6,765,224 B1
• Filed: 01/14/2003
• Issued: 07/20/2004
• Est. Priority Date: 12/29/2000
• Status: Expired due to Fees

• Current Assignee: Ametek Incorporated
• Original Assignee: Cognex Corporation
• Inventors: Favreau, Patrice, Wolinsky, Jeffrey, Jaaskelainen, Markku E.
• Primary Examiner(s): Le, Que T.
• Application Number:
  US10/341,678
• Time in Patent Office: 553 Days
• Field of Search: 250/208.1, 250/205, 250/559.44, 250/559.45, 250/559.39, 250/559.4, 356/429, 356/430, 356/237.1, 356/238.1, 356/238.2
• US Class Current: 250/559.4
• CPC Class Codes: G01N 2021/8909 Scan signal processing specially adapted for inspection of running sheets
• CPC Class Codes: G01N 21/8901 Optical details; Scanning details per se G02B

Abstract

A machine vision method and system for inspecting a material. The system comprises a light source arranged to illuminate the material and an imaging device configured to acquire image data corresponding to at least one characteristic of the material while the material is being illuminated by the light source. An image processor is configured to normalize the image data and to control adjustment of an exposure control level for the imaging device based upon the normalized image data. An exemplary method of implementing the machine vision system may include illuminating a material using a light source and obtaining image data corresponding to the material using an imaging device. The image data may be normalized and the adjustment of an exposure control level of the imaging device may be controlled based on the normalized image data.

Claims

1. A method of inspecting a continuous web material, the method comprising:

illuminating the material using a light source;

defining an exposure control level based on at least one characteristic of the material;

defining a normalization level based on the at least one characteristic of the material;

using an imaging device with the defined exposure control level and the defined normalization level to provide image data corresponding to the material; and

adjusting the exposure control level of the imaging device based on the image data.

2. The method of claim 1, the at least one characteristic of the material indicates a grade of the material.

3. The method of claim 1, the at least one characteristic of the material indicates multiple grades of the material.

4. The method of claim 1, wherein using an imaging device with the defined exposure control level and the defined normalization level to provide image data further comprises setting an initial exposure control level of the imaging device based on the at least one characteristic of the material.

5. The method of claim 1, further comprising normalizing the image data with at least one of an adaptive normalization and a static normalization.

6. The method of claim 5, wherein normalizing the image data comprises obtaining an average intensity level based on the at least one characteristic of the material.

7. The method of claim 6, wherein adjusting the exposure control level comprises comparing a measured intensity level of the image data to the average intensity level of the image data.

8. The method of claim 1, wherein the at least one characteristic of the material is determined based on optical properties of the material.

9. The method of claim 8, wherein the optical properties include reflectivity properties, transmissivity properties, or reflectivity and transmissivity properties.

10. A visual inspection system for inspecting a material, the system comprising:

a light source arranged to illuminate the material;

an imaging device configured to acquire image data corresponding to the material while the material is being illuminated by the light source;

the imaging device having an exposure control level based on at least one characteristic of the material; and

an image processor configured to normalize the image data and to control adjustment of an exposure control level for the imaging device based on the image data.

11. The system of claim 10, wherein the at least one characteristic of the material indicates a certain grade of the material.

12. The system of claim 10, further comprising:

a user interface configured to receive user input corresponding to an initial exposure control level.

13. The system of claim 12, wherein the imaging device acquires image data using the initial exposure control level.

14. The system of claim 13, wherein the image processor controls optional adjustment of the exposure control level away from the initial exposure control level based upon the intensity level of the image data.

15. The system of claim 13, wherein the exposure control level is measured using a scale of 10% to 100% on a per-pixel basis.