CAMERA BASED SIX DEGREE-OF-FREEDOM TARGET MEASURING AND TARGET TRACKING DEVICE WITH ROTATABLE MIRROR

• US 20070247615A1
• Filed: 04/20/2007
• Published: 10/25/2007
• Est. Priority Date: 04/21/2006
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Bridges, Robert E.
• Granted Patent: US 7,576,847 B2
• Time in Patent Office: Days
• US Class Current: 356/139.30
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01S 5/163 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49

Abstract

An embodiment may comprise a camera based target coordinate measuring system or apparatus for use in measuring the position of objects in manner that preserves a high level of accuracy. This high level of measurement accuracy is usually only associated with more expensive laser based devices. Many different arrangements are possible. Other embodiments may comprise related methods of using a camera based target coordinate measuring method for use in measuring the position of objects. Many variations on the methods are possible. For example, a camera based coordinate measuring system for use in measuring the position of a target relative to at least one frame of reference without requiring use of a laser range finder for measuring distance may comprise at least three or more light sources located on a target wherein the light sources are located on the target at known three-dimensional coordinates relative to each other; at least one rotatable mirror rotatable on about a first axis and a second axis; a camera located to receive light emitted by the light sources that is reflected off the minor; two angular measuring devices to measure the angles of rotation of the mirror about the first and second axes; and a processor for determining up to three positional degrees of freedom and up to three rotational degrees of freedom of the target.

Claims

1. A camera based target coordinate measuring system for use in measuring the position of objects without requiring use of a laser range finder for measuring distance comprising:

a mirror rotatable about a first axis and a second axis;

a camera located to receive light emitted by the light sources that is reflected off the mirror;

a target having at least three or more light sources wherein the light sources are located on the target at known three-dimensional coordinates relative to each other and wherein at least one of the light sources is located at a different distance from the mirror than the midpoint of a line segment connecting two of the other light sources, and wherein the target is structured to be placed on an object to be measured or to be placed on a device to measure the object;

two angular measuring devices to measure the angles of rotation of the mirror about the first and second axes;

at least one motor to rotate the mirror about the first and second axes;

a photosensitive pixel array located in the camera for recording images of the light sources on the target; and

a processor for directing the motor and for determining up to three positional degrees of freedom and up to three rotational degrees of freedom of the target.

2. A camera based target coordinate measuring method for use in measuring the position of objects without requiring use a laser range finder for measuring distance comprising:

operating a mirror rotatable about a first axis and a second axis;

operating a camera located to receive light emitted by the light sources that is reflected off the mirror;

placing a target to view with the mirror and having at least three or more light sources wherein the light sources are located on the target at known three-dimensional coordinates relative to each other and wherein at least one of the light sources is located at a different distance from the mirror than the midpoint of a line segment connecting two of the other light sources, and wherein the target is structured to be placed on an object to be measured or to be placed on a device to measure the object;

measuring angles of rotation of the mirror about the first and second axes with two angular measuring devices;

rotating the mirror about the first and second axes with at least one motor;

recording the images of the light sources on a photosensitive pixel array located in the camera; and

determining in a processor up to three positional degrees of freedom and up to three rotational degrees of freedom of the target.

3. The method of claim 2 wherein additional light sources on the target are illuminated or brought into view as needed to maintain accuracy as radial distance from the camera is increased.

4. A camera based coordinate measuring system for use in measuring the position of a target relative to at least one frame of reference without requiring use of a laser range finder for measuring distance comprising:

at least three or more light sources located on a target wherein the light sources are located on the target at known three-dimensional coordinates relative to each other;

at least one rotatable mirror rotatable on about a first axis and a second axis;

a camera located to receive light emitted by the light sources that is reflected off the mirror;

two angular measuring devices to measure the angles of rotation of the mirror about the first and second axes; and

a processor for determining up to three positional degrees of freedom and up to three rotational degrees of freedom of the target.

5. The system of claim 4 wherein the light sources are point light sources.

6. The system of claim 4 wherein the light sources are light emitting diodes (LED'"'"'s).

7. The system of claim 4 wherein the target is structured to be placed on an object to be measured or to be placed on a device to measure the object

8. The system of claim 4 further comprising:

two motors to rotate the mirror about the first and second axes.

9. The system of claim 4 wherein additional light sources are included on the target and are illuminated or brought into view as needed to increase accuracy as distance from the target to the mirror is increased.

10. The system of claim 4 wherein the light sources are located on the target at known three-dimensional coordinates relative to each other and wherein at least one of the light sources is located at a different distance from the mirror than the midpoint of a line segment connecting two of the other light sources, and wherein the target is structured to be placed on an object to be measured or to be placed on a device to measure the object.

11. The system of claim 4 wherein the target is structured to be placed on a probe having a probe tip in order to measure the three dimensional coordinates of an object brought into contact with the probe tip.

12. The system of claim 4 wherein the target is a spherically shaped target.

13. The system of claim 4 wherein the target is structured to be placed on a laser scanner unit.

14. The system of claim 4 wherein the target is structured to be placed on a coordinate measurement machine (CMM).

15. The system of claim 4 wherein the target is structured to be placed on a robotic arm.

16. The system of claim 4 wherein the target is incorporated in a tooling hole fiducial in order to determine the three dimensional coordinates of a tooling hole in an object.

17. The system of claim 4 wherein the target is structured to be placed on an articulated-arm coordinate measuring machine (CMM).