Method and system for improving ability of a machine vision system to discriminate features of a target

• US 7,305,115 B2
• Filed: 02/22/2002
• Issued: 12/04/2007
• Est. Priority Date: 02/22/2002
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Siemens Energy & Automation Incorporated (Siemens AG)
• Inventors: King, Steven Joseph
• Primary Examiner(s): Mehta; Bhavesh M
• Assistant Examiner(s): Seth; Manav
• Application Number:
  US10/081,127
• Publication Number:
  US 20030161524A1
• Time in Patent Office: 2,111 Days
• Field of Search: 382141-147, 700 95-212, 298/33, 348 86- 87, 348/92, 348 94- 95, 348125-128
• US Class Current: 382/141
• CPC Class Codes: G01N 21/33 using ultraviolet light G01N21/39 takes precedence
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G06V 10/143 Sensing or illuminating at different wavelengths
• CPC Class Codes: G06V 10/145 Illumination specially adapted for pattern recognition, e.g. using gratings

Abstract

A method and system is disclosed to improve the ability of a machine vision system to distinguish desired features of a target by taking images of the target under different one or more lighting conditions and using image analysis to extract information of interest about the target. Ultraviolet light is used alone or in connection with direct on-axis and/or low angle lighting to highlight different features of the target. One or more filters disposed between the target and the camera help to filter out unwanted light from the one or more images taken by the camera. The images may be analyzed by conventional image analysis techniques and the results recorded or displayed on a computer display device.

Claims

1. A system comprising

a camera;

a first visible spectrum illumination source;

at least a second ultraviolet spectrum illumination source; and

a computer, connected to the camera, to receive an image from the camera, wherein the camera is capable of taking a first image of a target illuminated by at least the first illumination source, and further capable of taking a second image of the target illuminated by at least the second illumination source and wherein the first and second images are able to be analyzed in the computer to determine an edge of at least a portion of the target.

2. The system of claim 1 wherein the camera comprises a video camera.

3. The system of claim 1 wherein the analysis by the computer comprises superposition of the first image and the second image.

4. The system of claim 1 wherein the first illumination source comprises a diffuse on axis light source.

5. The system of claim 1 further comprising at least one filter disposed between the target and the second illumination source, which filter blocks visible light.

6. The system of claim 5 wherein the filter blocks wavelengths of light greater than 390 nanometers.

7. The system of claim 1 further comprising at least one filter disposed between the camera and the target.

8. The system of claim 7 wherein the filter blocks ultraviolet light.

9. The system of claim 8 wherein the filter blocks light with a wavelength shorter than 410 nanometers.

10. The system of claim 9 wherein the filter blocks at least one portion of the visible spectrum.

11. A method comprising:

providing a camera connected to a computer having storage, an input to receive at least first and second images and an output providing extracted image information;

providing a filter disposed between the camera and the target, which filter blocks ultraviolet light;

using the camera to obtain a first image of the target and sending the image to the computer while the target is illuminated by a first visible spectrum illumination source comprising a diffuse on-axis light;

using the camera to obtain a second image of the target and sending the image to the computer while the target is illuminated by at least a second illumination source comprising an ultraviolet light; and

using the computer to analyze the first and second image to extract information about the target to determine an edge of at least a portion of the target.

12. A method comprising:

providing a camera connected to a computer having storage, an input to receive at least a first image, a second image, and an output providing extracted image information;

providing a visible light filter disposed between the camera and the target, which visible light filter blocks visible light;

providing an ultraviolet light filter disposed between the camera and the target, which ultraviolet light filter blocks ultraviolet light;

using the camera to obtain a first image of the target and sending the image to the computer while the target is illuminated by a first illumination source comprising an ultra-violet light and the visible light filter is provided;

using the camera to obtain a second image of the target and sending the image to the computer while the target is illuminated by said first illumination source and the ultraviolet light filter is provided; and

using the computer to analyze the first image and the second image to extract edge information about the target.

13. A system comprising

a camera;

a first target illumination source comprising a visible light source;

a second target illumination source comprising an ultra-violet light source;

a filter disposed between the camera and said target; and

a computer, connected to the camera, to receive an image from the camera, wherein the camera is capable of taking at least first image of said target illuminated by said ultraviolet light source and second image of said target illuminated by said visible light source, and wherein the first image and second image are able to be analyzed in the computer to extract dimensional information about the target.