Detection of multiple targets on a plane of interest

• US 20070116333A1
• Filed: 11/18/2005
• Published: 05/24/2007
• Est. Priority Date: 11/18/2005
• Status: Active Grant

• Current Assignee: Accenture Global Services Limited (Accenture PLC)
• Original Assignee: Accenture Global Services GmbH (Accenture PLC)
• Inventors: Dempski, Kelly, Harvey, Brandon
• Granted Patent: US 7,599,520 B2
• Time in Patent Office: Days
• US Class Current: 382/128
• CPC Class Codes: G06F 3/0428 by sensing at the edges of the touch surface the interruption of optical paths, e.g. an illumination plane, parallel to the touch surface which may be virtual sensing beam interruptions in a planar beam grid of an optical touch-screen G06F3/0421
• CPC Class Codes: G06T 7/593 from stereo images

Abstract

A system and method for determining positions of multiple targets on a planar surface is described. The targets subject to detection may include a touch from a body part (such as a finger), a pen, or other objects. The system and method may use light sensors, such as cameras, to generate information for the multiple simultaneous targets (such as finger, pens, etc.) that are proximate to or on the planar surface. The information from the cameras may be used to generate possible targets. The possible targets include both “real” targets (a target associated with an actual touch) and “ghost” targets (a target not associated with an actual touch). Using analysis, such as a history of previous targets, the list of potential targets may then be narrowed to the multiple targets by analyzing state information for targets from a previous cycle (such as the targets determined during a previous frame).

Claims

1. A camera-based system for detecting positions of multiple simultaneous targets on a substantially planar surface comprising:

at least two cameras positioned relative to the planar surface to acquire images of the multiple simultaneous targets on the planar surface; and

computer-readable memory having stored thereon logic for receiving data indicative of images of the multiple simultaneous targets, determining potential positions using triangulation, the potential positions comprising positions for the multiple simultaneous targets and positions for targets not associated with a touch on the planar surface, and analyzing the potential positions to determine which, of the potential positions, comprise the positions for the multiple simultaneous targets.

2. The system of claim 1, wherein a target is registered as an occlusion in the image acquired by the cameras;

and

wherein the logic for determining the potential positions using triangulation comprises logic for selecting one of the at least two cameras and iterating the following logic for each occlusion for the selected camera;

determining a ray corresponding to the occlusion for the selected camera; and

determining rays corresponding to the occlusions for an unselected camera; and

triangulating the ray corresponding to the occlusion for the selected camera and the rays corresponding to the occlusions for the unselected camera to determine the potential positions.

3. The system of claim 1, wherein the logic for analyzing the potential positions to determine the positions for the multiple simultaneous targets comprises logic for determining whether the potential positions are related to a target previously identified.

4. The system of claim 3, wherein the cameras provide information in sequential image frames;

and

wherein the target previously identified comprises a target identified in a previous frame.

5. The system of claim 4, wherein the target identified in a previous frame includes a position of the target in the previous frame;

and

wherein the logic for determining whether the potential positions are related to a target previously identified comprises logic for comparing the potential positions with the position of the target in the previous frame.

6. The system of claim 5, wherein the logic for comparing the potential positions with the position of the target in the previous frame comprises:

logic for determining the potential position closest to the position of the target in the previous frame; and

logic for designating the potential position closest to the position of the target in the previous frame as related to the target in the previous frame.

7. The system of claim 4, wherein the multiple simultaneous targets are sensed in a current frame;

and

wherein the logic for determining whether the potential positions are related to a target previously identified comprises logic for comparing the potential positions with an expected position of the target in a current frame.

8. The system of claim 7, wherein the logic for comparing the potential positions with an expected position of the target in a current frame comprises:

logic for determining the potential position closest to the expected position of the target in the previous frame; and

logic for designating the potential position closest to the expected position of the target in the previous frame as related to the target in the previous frame.

9. The system of claim 3, wherein the logic for analyzing the potential positions to determine the positions for the multiple simultaneous targets comprises logic for:

determining rays formed between the potential positions and their related target previously identified; and

comparing the rays to determine if any rays are identical.

10. The system of claim 9, wherein the logic for analyzing the potential positions to determine the positions for the multiple simultaneous targets further comprises logic for:

determining for the potential positions whose rays are identical which potential position has a longer history with the target previously identified; and

identifying the potential position with the longer history with the target previously identified as one of the multiple simultaneous targets.

11. The system of claim 1, wherein the logic for analyzing the potential positions to determine the positions for the multiple simultaneous targets comprises logic for determining whether the potential positions are within a 2-dimensional boundary of the planar surface.

12. The system of claim 1, further comprising logic for determining a distance between the positions for the multiple simultaneous targets.

13. The system of claim 12, further comprising logic for:

comparing the distance with a predetermined minimum distance; and

determining which of the multiple simultaneous targets has a shorter history if the distance is less than the predetermined minimum; and

deleting the multiple simultaneous target with the shorter history.

14. A method for detecting positions of multiple simultaneous targets on a substantially planar surface using at least two cameras positioned relative to the planar surface, the method comprising:

acquiring an image by the at least two cameras of the multiple simultaneous targets on the planar surface;

determining potential positions using triangulation, the potential positions comprising positions for the multiple simultaneous targets and positions for targets not associated with a touch on the planar surface; and

analyzing the potential positions to determine which, of the potential positions, comprise the positions for the multiple simultaneous targets.

15. The method of claim 14, wherein a target is registered as an occlusion in an image acquired by the camera;

and

wherein determining the potential positions using triangulation comprises selecting one of the at least two cameras and iterating for each occlusion for the selected camera;

determining a ray corresponding to the occlusion for the selected camera; and

determining rays corresponding to the occlusions for an unselected camera; and

triangulating the ray corresponding to the occlusion for the selected camera and the rays corresponding to the occlusions for the unselected camera to determine the potential positions.

16. The method of claim 14, wherein analyzing the potential positions to determine the positions for the multiple simultaneous targets comprises determining whether the potential positions are related to a target previously identified.

17. The method of claim 16, wherein the cameras provide information in sequential frames;

and

wherein the target previously identified comprises a target identified in a previous frame.

18. The method of claim 17, wherein the target identified in a previous frame includes a position of the target in the previous frame;

and

wherein determining whether the potential positions are related to a target previously identified comprises comparing the potential positions with the position of the target in the previous frame.

19. The method of claim 17, wherein the multiple simultaneous targets are sensed in a current frame;

and

wherein determining whether the potential positions are related to a target previously identified comprises comparing the potential positions with an expected position of the target in a current frame.

20. The method of claim 16, wherein analyzing the potential positions to determine the positions for the multiple simultaneous targets comprises:

determining rays formed between the potential positions and their related target previously identified; and

comparing the rays to determine if any rays are identical.

21. The method of claim 20, wherein analyzing the potential positions to determine the positions for the multiple simultaneous targets further comprises:

determining for the potential positions whose rays are identical which potential position has a longer history with the target previously identified; and

identifying the potential position with the longer history with the target previously identified as one of the multiple simultaneous targets.

22. The method of claim 14, wherein analyzing the potential positions to determine the positions for the multiple simultaneous targets comprises determining whether the potential positions are within a 2-dimensional boundary of the planar surface.

23. The method of claim 14, further comprising determining a distance between the positions for the multiple simultaneous targets.

24. The method of claim 23, further comprising:

comparing the distance with a predetermined minimum distance; and

determining which of the multiple simultaneous targets has a shorter history if the distance is less than the predetermined minimum; and

deleting the multiple simultaneous target with the shorter history.