SYSTEM AND METHOD FOR TRACKING A LASER SPOT ON A PROJECTED COMPUTER SCREEN IMAGE

• US 20080266253A1
• Filed: 04/25/2007
• Published: 10/30/2008
• Est. Priority Date: 04/25/2007
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Seeman, Lisa, Dolfi, David
• Granted Patent: US 7,872,637 B2
• Time in Patent Office: Days
• US Class Current: 345/158
• CPC Class Codes: G06F 3/0346 with detection of the device orientation or free movement in a 3D space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors
• CPC Class Codes: G06F 3/0386 for light pen

Abstract

A system and method for tracking a laser spot on a projected computer screen image computes a projective transformation matrix using the projected computer screen image electronically captured in a frame of image data. The projective transformation matrix is computed by fitting a polygon to a contour of each graphical object in the frame of image data and determining whether the polygon for each graphical object satisfies a set of predefined parameters to find a candidate polygon that corresponds to an outline of the projected computer screen image in the frame of image data.

Claims

1. A method for tracking a laser spot on a projected computer screen image, said method comprising:

electronically capturing said projected computer screen image on a projection surface in a frame of image data;

fitting a polygon to a contour of each graphical object in said frame of image data;

determining whether said polygon for each graphical object satisfies a set of predefined parameters to find a candidate polygon that corresponds to an outline of said projected computer screen in said frame of image data; and

computing a projective transformation matrix using corners of said candidate polygon, said projective transformation matrix including mapping information to track said laser spot on said projected computer screen image.

2. The method of claim 1 wherein said determining includes determining whether said polygon for each graphical object satisfies a predefined parameter with respect to one of number of vertices, angles between adjacent sides, and convexity.

3. The method of claim 2 wherein said determining whether said polygon for each graphical object satisfies said set of predefined parameters includes determining whether the number of vertices of said polygon for each graphical object equals four.

4. The method of claim 2 wherein said determining whether said polygon for each graphical object satisfies said set of predefined parameters includes determining whether angles of adjacent sides of said polygon for each graphical object are approximately between eighty degrees and one hundred degrees.

5. The method of claim 1 wherein said determining includes determining whether said polygon for each graphical object satisfies a predefined parameter with respect to one of area and aspect ratio.

6. The method of claim 5 wherein said determining whether said polygon for each graphical object satisfies said set of predefined parameters includes determining whether the area of said polygon for each graphical object is approximately between fifty percent and nine-five percent of the size of said frame of image data.

7. The method of claim 5 wherein said determining whether said polygon for each graphical object satisfies said set of predefined parameters includes determining whether the aspect ratio of said polygon for each graphical object is approximately one of 3:

4 and 6;

9.

8. The method of claim 1 further comprising converting said frame of image data from a color image frame into a binary image frame.

9. The method of claim 8 wherein said converting includes:

converting said frame of image data from said color image frame into a grayscale image frame;

down-sampling and then up-sampling said grayscale image frame; and

converting said grayscale image frame into said binary image frame.

10. The method of claim 1 further comprising:

filtering incoming light based on wavelength, including transmitting said incoming light within a selected wavelength range and filtering out said incoming light not within said selected wavelength range;

electronically capturing at least a portion of said projection surface in another frame of image data using said incoming light; and

processing said another frame of image data to track said laser spot in said another frame of image data using said projective transformation matrix computing position.

11. A laser pointer tracking system comprising:

an image sensor to electronically capture a projected computer screen image on a projection surface in frames of image data; and

a laser pointer tracking module operatively coupled to said image sensor, said laser pointer tracking module being configured to fit a polygon to a contour of each graphical object in a particular frame of image data, said laser pointer tracking module being also configured to determine whether said polygon for each graphical object satisfies a set of predefined parameters to find a candidate polygon that corresponds to an outline of said projected computer screen in said particular frame of image data, said laser pointer tracking module being further configured to compute a projective transformation matrix using corners of said candidate polygon, said projective transformation matrix including mapping information to track said laser spot on said projected computer screen image.

12. The system of claim 11 wherein said laser pointer tracking module is configured to determine whether said polygon for each graphical object satisfies a predefined parameter with respect to one of number of vertices, angles between adjacent sides, and convexity.

13. The system of claim 11 wherein said laser pointer tracking module is configured to determine whether said polygon for each graphical object satisfies a predefined parameter with respect to one of area and aspect ratio.

14. The system of claim 11 wherein said laser pointer tracking module is configured to convert said frame of image data from a color image frame into a binary image frame.

15. The system of claim 14 wherein said laser pointer tracking module is configured to convert said frame of image data from said color image frame into a grayscale image frame, down-sample and then up-sample said grayscale image frame, and convert said grayscale image frame into said binary image frame.

16. The system of claim 11 further comprising an optical bandpass filter optically coupled to said image sensor, said optical bandpass filter being configured to transmit light within a selected wavelength range that corresponds to a wavelength range of a particular laser light.

17. A method for tracking a laser spot on a projected computer screen image, the method comprising:

electronically capturing said projected computer screen image on said projection surface in a color image;

converting said color image into a binary image;

fitting a polygon to a contour of each graphical object in said binary image;

determining whether said polygon for each graphical object satisfies a set of predefined parameters to find a candidate polygon that corresponds to an outline of said projected computer screen in said binary image; and

computing a projective transformation matrix using corners of said candidate polygon, said projective transformation matrix including mapping information to track said laser spot on said projected computer screen image.

18. The method of claim 17 wherein said determining includes determining whether said polygon for each graphical object satisfies a predefined parameter with respect to one of number of vertices, angles between adjacent sides, and convexity.

19. The method of claim 17 wherein said determining includes determining whether said polygon for each graphical object satisfies a predefined parameter with respect to one of area and aspect ratio.

20. The method of claim 17 wherein said converting includes:

converting said color image into a grayscale image;

down-sampling and then up-sampling said grayscale image; and

converting said grayscale image into said binary image.