Automated lens calibration

• US 20030035100A1
• Filed: 03/25/2002
• Published: 02/20/2003
• Est. Priority Date: 08/02/2001
• Status: Abandoned Application

• Current Assignee: Cyra Technologies, Inc. (Hexagon AB)
• Original Assignee: Cyra Technologies, Inc. (Hexagon AB)
• Inventors: Williams, Rick, Chen, William, Dimsdale, Jerry
• Application Number:
  US10/106,018
• Publication Number:
  US 20030035100A1
• Time in Patent Office: Days
• US Class Current: 356/124
• CPC Class Codes: G06T 7/80 Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
• CPC Class Codes: H04N 17/002 for television cameras

Abstract

An improved approach for correcting lens distortion in an imaging system is disclosed. The method is applicable to systems which include both an image system and a laser scanner. In the method, a comparison is made between the location of laser spots on a remote image as captured by the imaging system with calculated locations of the laser spots generated by the laser scanner. The difference between distorted imaged spots and undistorted computationally determined spot locations is utilized to generate a distortion map. The distortion map is then applied to correct a distorted image.

Claims

1. An imaging apparatus comprising:

a camera including an imaging array and a lens system for projecting an image of an object onto the array, said lens system inducing some distortion in the projected image;

a laser for generating a laser beam;

a scanner for scanning the laser beam over the object in a manner so that laser light reflected from the object is imaged by the lens system onto the array, said scanner generating information corresponding to the position of the laser beam on the object; and

a processor for controlling the scanner and for comparing the position of the laser light imaged by the camera onto the array with position information received from the scanner to determine the distortion in the image induced by the lens system.

2. An apparatus as recited in claim 1 further including a display for displaying the image from the array and wherein said processor modifies the image to compensate for the determined distortion.

3. An apparatus as recited in claim 2 wherein distortion information is stored and recalled by the processor to correct distortion in subsequent images.

4. An apparatus as recited in claim 1 wherein the laser is pulsed and directed to generate a plurality of illuminated spots on the object.

5. An apparatus as recited in claim 4 wherein the illuminated spots used to determine distortion fall along a line.

6. An apparatus as recited in claim 4 wherein the illuminated spots used to determine distortion fall on a grid pattern.

7. An apparatus as recited in claim 1 wherein the scanner is controlled to generate a cluster of illuminated laser spots on the object to facilitate detection at the array.

8. An apparatus as recited in claim 7 wherein the processor determines the center of the cluster of spots using centroid or moment algorithm.

9. An apparatus as recited in claim 7 wherein the cluster of spots is configured based on the resolution of the image array.

10. An apparatus as recited in claim 1 wherein an image of the object is obtained when the laser is not illuminating the object and wherein that image is used by the processor to enhance the imaging of the laser light.

11. An apparatus as recited in claim 10 wherein the image of the object which is obtained when the laser is not illuminating the object is subtracted from the image of the object when the laser is illuminating the object.

12. An apparatus as recited in claim 1 wherein processor uses information from the scanner to generate a model of the object and wherein corrected image information is used to add texture to the model.

13. A method of determining the distortion created by the lens system of a camera, wherein said lens system projects an image onto an array, said method comprising the steps of:

directing a laser beam to reflect off an object in a manner so that the reflected light is imaged by the array; and

comparing the position of the laser light falling on the array with independent information about the position of the laser beam on the object to determine the imaging model of and distortion created by the lens system.

14. A method of determining the distortion created by the lens system of a camera, wherein said lens system projects an image onto an array, said method comprising the steps of:

directing a laser beam with a scanner to reflect off an object in a manner so that the reflected light is imaged by the array, said scanner generating position information; and

comparing the position of the laser light falling on the array with position information generated by the scanner to determine the distortion created by the lens system.

15. The method of claim 14 further including the step of displaying an image based on the light imaged by the array, with the image being modified in response to the determination of said distortion of said lens system.

16. A method as recited in claim 14 wherein the distortion information which has been determined is stored and later recalled to correct distortion in subsequent images.

17. A method as recited in claim 14 wherein the scanner is controlled to generate a cluster of illuminated laser spots on the object to facilitate detection at the array.

18. A method as recited in claim 17 wherein the center of the cluster of spots is determined using centroid or moment algorithm.

19. A method as recited in claim 14 further including the step of obtaining an image of the object when the laser is not illuminating the object and wherein that image is used to enhance the imaging of the laser light.

20. A method as recited in claim 19 wherein the image of the object which is obtained when the laser is not illuminating the object is subtracted from the image of the object when the laser is illuminating the object.

21. An imaging apparatus comprising:

a camera including an imaging array and a lens system for projecting an image of an object onto the array;

a laser for generating a laser beam;

a scanner for scanning the laser beam over the object in a manner so that laser light reflected from the object is imaged by the lens system onto the array, said scanner generating information corresponding to the position of the laser beam on the object; and

a processor for controlling the scanner and for comparing the position of the laser light imaged by the camera onto the array with position information received from the scanner to determine an optical imaging model of the camera.