SYSTEM AND METHOD FOR OPTICALLY TRACKING A MOBILE DEVICE

• US 20100266158A1
• Filed: 12/20/2007
• Published: 10/21/2010
• Est. Priority Date: 12/20/2007
• 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: Chong, Yik Leong, Tan, Meng Whui, Lim, Teng Hun, Saxena, Kuldeep Kumar
• Granted Patent: US 7,957,558 B2
• Time in Patent Office: Days
• US Class Current: 382/103
• CPC Class Codes: G05D 1/0253 extracting relative motion information from a plurality of images taken successively, e.g. visual odometry, optical flow determining position or orientation from images G06T7/70
• CPC Class Codes: G06T 2207/30244 Camera pose
• CPC Class Codes: G06T 2207/30252 Vehicle exterior; Vicinity of vehicle
• CPC Class Codes: G06T 7/73 using feature-based methods

Abstract

A system and method for optically tracking a mobile device uses a first displacement value along a first direction and a second displacement value along a second direction, which are produced using frames of image data of a navigation surface, to compute first and second tracking values that indicate the current position of the mobile device. The first tracking value is computed using the second displacement value and the sine of a tracking angle value, while the second tracking value is computed using the second displacement value and the cosine of the tracking angle value. The tracking angle value is an angle value derived using at least one previous second displacement value.

Claims

1. A system for optically tracking a mobile device comprising:

a light source configured to emit illumination light toward a navigation surface;

an image sensor array positioned to receive the illumination light reflected from the navigation surface, the image sensor array being configured to generate frames of image data in response to the received illumination light;

a navigation engine operably connected to the image sensor array to receive the frames of image data, the navigation engine being configured to correlate the frames of image data to produce a first displacement value along a first direction and a second displacement value along a second direction; and

a tracking module operably connected to the navigation engine to receive the first and second displacement values to compute first and second tracking values that indicate the current position of the mobile device, the tracking module being configured to compute the first tracking value using the second displacement value and the sine of a tracking angle value and to compute the second tracking value using the second displacement value and the cosine of the tracking angle value, the tracking angle value being an angle value derived using at least one previous second displacement value.

2. The system of claim 1 further comprising a second light source configured to emit another illumination light toward the navigation surface at a different angle than the angle of the illumination light.

3. The system of claim 1 wherein the tracking module is configured to compute the first tracking value using the second displacement value multiplied by the sine of the tracking angle value and to compute the second tracking value using the second displacement value multiplied by the cosine of the tracking angle value, the tracking module being configured to compute the tracking angle value using the first and second displacement values.

4. The system of claim 1 wherein the tracking module is configured to compute the first and second tracking values using a summed second value of multiple second displacement values from the navigation engine and to update the tracking angle value using the summed second value and a summed first value of multiple first displacement values from the navigation engine.

5. The system of claim 4 wherein the tracking module is configured to compute the first tracking value using the summed second value multiplied by the sine of the tracking angle value and to compute the second tracking value using the summed second value multiplied by the cosine of the tracking angle value.

6. The system of claim 1 further comprising a second image sensor array and a second navigation engine that are configured to generate another first and second displacement values, wherein the tracking module is configured to compute the first and second tracking values using an average value derived from the second displacement value and the another second displacement value, the tracking module being also configured to update the tracking angle value using the average value.

7. The system of claim 6 wherein the tracking module is configured to compute the first tracking value using the average value multiplied by the sine of the tracking angle value and to compute the second tracking value using the average value multiplied by the cosine of the tracking angle value, the average value being the average of the second displacement value and the another second displacement value.

8. The system of claim 6 wherein the tracking module is configured to compute the first tracking value using the average value multiplied by the sine of the tracking angle value and to compute the second tracking value using the average value multiplied by the cosine of the tracking angle value, the average value being the average of a summed second value and a summed another second value, the summed second value being the sum of multiple second displacement values from the navigation engine, the summed another second value being the sum of multiple another second displacement values from the second navigation engine.

9. A method for optically tracking a mobile device, the method comprising:

electronically capturing frames of image data of a navigation surface;

correlating the frames of image data to produce a first displacement value along a first direction and a second displacement value along a second direction; and

computing first and second tracking values that indicate the current position of the mobile device using the first and second displacement values, the first tracking value being computed using the second displacement value and the sine of a tracking angle value, the second tracking value being computed using the second displacement value and the cosine of the tracking angle value, the tracking angle value being an angle value derived using at least one previous second displacement value.

10. The method of claim 9 wherein the electronically capturing the frame of image data includes emitting illumination light toward the navigation surface.

11. The method of claim 9 wherein the computing the first and second tracking values includes:

computing the first tracking value using the second displacement value multiplied by the sine of the tracking angle value;

computing the second tracking value using the second displacement value multiplied by the cosine of the tracking angle value; and

updating the tracking angle value using the first and second displacement values.

12. The method of claim 9 wherein the computing the first and second tracking values includes:

computing the first and second tracking values using a summed second value of multiple second displacement values; and

updating the tracking angle value using the summed second value and a summed first value of multiple first displacement values.

13. The method of claim 12 wherein the computing the first and second tracking values includes:

computing the first tracking value using the summed second value multiplied by the sine of the tracking angle value; and

computing the second tracking value using the summed second value multiplied by the cosine of the tracking angle value.

14. The method of claim 9 further comprising:

electronically capturing additional frames of image data of the navigations surface; and

correlating the additional frames of image data to produce another first displacement value along the first direction and another second displacement value along the second direction,

wherein the computing the first and second tracking values includes computing the first and second tracking values using an average value derived from the second displacement value and the another second displacement value.

15. The method of claim 14 wherein the computing the first and second tracking values includes:

computing the first tracking value using the average value multiplied by the sine of the tracking angle value; and

computing the second tracking value using the average value multiplied by the cosine of the tracking angle value,

wherein the average value is the average of the second displacement value and the another second displacement value.

16. The method of claim 14 wherein the computing the first and second tracking values includes:

computing the first tracking value using the average value multiplied by the sine of the tracking angle value; and

computing the second tracking value using the average value multiplied by the cosine of the tracking angle value,

wherein the average value is the average of a summed second value and a summed another second value, the summed second value being the sum of multiple second displacement values, the summed another second value being the sum of multiple another second displacement values.

17. The method of claim 9 further comprising monitoring an intensity value associated with one of more of the frames of image data to adjust the intensity of illumination light used to electronically capture the frame of image data.

18. A method for optically tracking a mobile device, the method comprising:

emitting illumination light toward a navigation surface;

receiving the illumination light reflected from the navigation surface;

producing frames of image data in response to the received illumination light;

correlating the frames of image data to produce a first displacement value along a first direction and a second displacement value along a second direction; and

computing first and second tracking values that indicate the current position of the mobile device using the first and second displacement values, the first tracking value being computed using the second displacement value and the sine of a tracking angle value, the second tracking value being computed using the second displacement value and the cosine of the tracking angle value, the tracking angle value being an angle value derived using at least one previous second displacement value.

19. The method of claim 18 wherein the computing the first and second tracking values includes:

computing the first tracking value using a selected value multiplied by the sine of the tracking angle value, the selected value being the second displacement value or the sum of the second displacement value and one or more previous second displacement values; and

computing the second tracking value using the selected value multiplied by the cosine of the tracking angle value.

20. The method of claim 18 further comprising:

producing additional frames of image data in response additional illumination light reflected from the navigation surface; and

correlating the additional frames of image data to produce another first displacement value along the first direction and another second displacement value along the second direction,

wherein the computing the first and second tracking values includes;

computing the first tracking value using a selected value multiplied by the sine of the tracking angle value, the selected value being an average value of the second displacement value and the another second displacement value or a summed second displacement value and a summed another second displacement value, the summed second displacement value being the sum of multiple second displacement values, the summed another second displacement value being the sum of multiple another second displacement values; and

computing the second tracking value using the selected value multiplied by the cosine of the tracking angle value.