Light pipe illumination system and method

• US 8,061,614 B2
• Filed: 10/08/2010
• Issued: 11/22/2011
• Est. Priority Date: 10/24/2003
• Status: Expired due to Fees

• Current Assignee: Cognex Technology & Investment Corporation (Cognex Corporation)
• Original Assignee: Cognex Technology & Investment Corporation (Cognex Corporation)
• Inventors: Testa, Justin, Gerst, Carl W. III, Equitz, William H., Nadabar, Sateesh
• Primary Examiner(s): TRAIL, ALLYSON NEEL
• Application Number:
  US12/900,593
• Publication Number:
  US 20110024504A1
• Time in Patent Office: 410 Days
• Field of Search: 235/455, 235/472.01, 235/472.02, 235/462.42, 385/43, 250/234, 710/300
• US Class Current: 235/455
• CPC Class Codes: G02B 6/0096 the lights guides being of the hollow type
• CPC Class Codes: G06K 2007/10485 Arrangement of optical elements
• CPC Class Codes: G06K 2207/1011 Aiming
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/1404 Methods for optical code recognition

Abstract

A system and method is provided for illuminating a subject using a light pipe that transmits light from a source, such as an LED ring illuminator to an outlet that directs the light appropriately as either bright field illumination, dark field illumination or both. The light pipe can include concentric cylinders, typically with a bright field illuminator nested within a dark field illuminator. The tip of the dark field illuminator may be angled so as to internally reflect light inwardly toward the central optical axis of a camera at a low angle. The tip can be located near the focal plane of the camera for the desired field of view. The field of view of the camera sensor can be modified to reject data outside of a illumination field of a particular shape. This illumination field can be created by shaping the light pipe in a predetermined form that projects the modified illumination field. Likewise, a set of aiming illuminators (in, for example, a noticeable color) can be provided around the perimeter of the light pipe to delineate outer boundaries of the illumination field or area of interest. These approaches facilitate better aiming of the sensor into the desired area of interest so that it is illuminated and/or acquired most-fully.

Claims

1. An image acquisition system including an image sensor for imaging at least a portion of a subject, the system comprising:

a light pipe defining an inner lumen through which the image sensor views the subject;

a light source in alignment with a proximal portion of the light pipe, the light source adapted to project a light into the light pipe and through the light pipe, the light pipe including a distal portion adapted to provide a high-angle bright field illumination pattern on the subject with a first portion of the light and to reflect a second portion of the light to provide a low-angle dark field illumination pattern on the subject.

2. The image acquisition system according to claim 1 wherein the light pipe and the light source are each mounted on a handheld scanning appliance.

3. The image acquisition system according to claim 1 further comprising a set of light sources that each project a beam at a predetermined point with respect to the subject to thereby assist aiming of the image sensor at the subject.

4. The image acquisition system according to claim 1 wherein the light pipe is cylindrical.

5. The image acquisition system according to claim 1 wherein the light pipe is rectangular.

6. The image acquisition system according to claim 1 wherein the light pipe is oval.

7. The image acquisition system according to claim 1 wherein the light pipe defines a shape that reduces a field of view of the image sensor.

8. The image acquisition system according to claim 1 wherein the light pipe defines a curved shape.

9. The image acquisition system according to claim 1 wherein the light pipe defines a shape conforming to dimensions of the subject.

10. The image acquisition system according to claim 1 further including an electronic controller that selectively controls predetermined portions of the light source to provide selective illumination to portions of the light pipe.

11. The image acquisition system according to claim 1 wherein the light pipe includes an outer tube and an inner tube.

12. The image acquisition system according to claim 11 wherein the outer tube and the inner tube are cylindrical.

13. The image acquisition system according to claim 11 wherein the outer tube and the inner tube are rectangular.

14. The image acquisition system according to claim 11 wherein the outer tube and the inner tube are oval.

15. The image acquisition system according to claim 11 wherein the outer tube and inner tube are mounted on a handheld scanning appliance.

16. The image acquisition system according to claim 11 wherein the inner tube defines a shape that reduces a field of view of the image sensor.

17. The image acquisition system according to claim 11 wherein the inner tube defines a curved shape.

18. The image acquisition system according to claim 11 wherein the inner tube defines a shape conforming to dimensions of a predetermined subject.

19. The image acquisition system according to claim 11 further comprising a set of light sources that each project a beam at a predetermined point with respect to the subject to thereby assist aiming of the image sensor at the subject.