Processing methods for speckle-based motion sensing

• US 8,263,921 B2
• Filed: 08/06/2007
• Issued: 09/11/2012
• Est. Priority Date: 08/06/2007
• Status: Active Grant

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Lang, Robert J., Todoroff, Brian, Xu, Yansun, Bailey, Jeffry C.
• Primary Examiner(s): LEE, JOHN R
• Application Number:
  US11/890,651
• Publication Number:
  US 20090040062A1
• Time in Patent Office: 1,863 Days
• Field of Search: 250/206.2, 250/221, 345/166, 702/66, 702/189, 702/198, 702/199, 708/445
• US Class Current: 250/206.2
• CPC Class Codes: G06F 3/0317 in co-operation with a patterned surface, e.g. absolute position or relative movement detection for an optical mouse or pen positioned with respect to a coded surface
• CPC Class Codes: G06F 3/03543 Mice or pucks G06F3/03541 takes precedence
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry

Abstract

One embodiment relates to a method of tracking motion using a speckle-based motion sensor. A distance moved is determined by a first signal processing procedure, and a distance moved is determined by a second signal processing procedure. Selection between said distances is made based on whether the distance determined by the first signal processing procedure exceeds a predetermined threshold distance. According to a preferred embodiment, the first signal processing procedure makes a more accurate determination of distance for slower speeds, while the second signal processing procedure makes a more accurate determination of distance for higher speeds. Other embodiments, aspects and features are also disclosed.

Claims

1. A method of tracking motion relative to a surface using a speckle-based motion sensor, the method comprising:

creating on the surface a plurality of speckle patterns based on movement of the surface along at least two nonparallel axes relative to a plurality of optical detectors;

detecting said plurality of speckle patterns with said plurality of optical detectors;

creating a set of electrical signals emitted from said optical detectors, such that said electrical signals based on the detected speckle patterns and vary quasi periodically with the distance moved along the at least two non-parallel axes;

sampling said electrical signals at a plurality of discrete times extending over a time interval, creating a plurality of sampled electrical signals; and

processing said plurality of sampled electrical signals to determine a distance moved during said time interval,

wherein the creating a set of electrical signals includes creating one or more sets of phase signals based on the electrical signals, the phase signals responsive to relative phases of the speckle patterns, and the phase signals are quasi-periodic with the distance moved, and

wherein said processing of said plurality of sampled electrical signals includes multiplying the values of signals from one time interval by the values of signals from an adjacent interval to form signal products, and adding or subtracting pairs of said signal products to form at least one b-vector.

2. The method of claim 1 wherein said processing of said plurality of sampled electrical signals includes dividing said time interval into subintervals and summing the values of said electrical signals within each of said subintervals.

3. The method of claim 1, wherein said processing of said plurality of sampled electrical signals includes:

representing pairs of said electrical signals as a complex phasor and computing the phase of said phasor at each of said discrete times; and

computing a distance moved from the differences in the values of said phases at two different discrete times.

4. The method of claim 1, wherein said processing of said plurality of sampled electrical signals includes:

computing a b-vector for a first subset of said optical detectors;

computing a b-vector for a second subset of said optical detectors; and

summing said two b-vectors.

5. The method of claim 1, wherein said processing of said plurality of sampled electrical signals includes the step of computing a first b-vector at a first time and computing a second b-vector at a second time and summing said two b-vectors.

6. The method of claim 1, wherein said processing of said plurality of sampled electrical signals includes:

computing a first b-vector from two sets of sampled electrical signals separated by a time interval T1; and

computing a second b-vector from two sets of sampled electrical signals separated by a time interval T2, where T1 is not equal to T2.

7. The method of claim 1, wherein said processing of said plurality of sampled electrical signals includes:

defining the signals from a first discrete time as a reference set of signals computing distance moved since said reference set of signals; and

updating said reference set when said distance moved exceeds a predefined threshold.

8. The method of claim 1, wherein said processing of said plurality of sampled electrical signals includes:

computing distance moved at a plurality of discrete times;

replacing a value of said distance moved if the difference between the computed value of said distance moved differs from the values computed for other times within said plurality by more than a specified amount.

9. The method of claim 1, wherein said processing of said plurality of sampled electrical signals includes reporting no motion if the magnitude of one or more or a combination of said electrical signals falls below a predefined threshold.

10. The method of claim 8, wherein said processing of said plurality of sampled electrical signals includes:

computing a plurality of b-vectors for a plurality of discrete times;

summing said b-vectors to form a resultant b-vector; and

reporting no motion if the magnitude of said resultant b-vector falls below a predefined threshold.

11. A method of tracking motion relative to a surface using a speckle-based motion sensor, the method comprising:

creating on the surface a plurality of speckle patterns based on movement of the surface along at least two nonparallel axes relative to a plurality of optical detectors;

detecting said plurality of speckle patterns with said plurality of optical detectors;

creating a set of electrical signals emitted from said optical detectors, such that said electrical signals based on the detected speckle patterns and vary quasi periodically with the distance moved along the at least two non-parallel axes;

sampling said electrical signals at a plurality of discrete times extending over a time interval, creating a plurality of sampled electrical signals; and

processing said plurality of sampled electrical signals to determine a distance moved during said time interval,

wherein said processing of said plurality of sampled electrical signals includes multiplying the values of signals from one time interval by the values of signals from an adjacent interval to form signal products, and adding or subtracting pairs of said signal products to form at least one b-vector.

12. The method of claim 11 wherein said processing of said plurality of sampled electrical signals includes dividing said time interval into subintervals and summing the values of said electrical signals within each of said subintervals.

13. The method of claim 11, wherein said processing of said plurality of sampled electrical signals includes:

representing pairs of said electrical signals as a complex phasor and computing the phase of said phasor at each of said discrete times; and

computing a distance moved from the differences in the values of said phases at two different discrete times.

14. The method of claim 11, wherein said processing of said plurality of sampled electrical signals includes:

computing a b-vector for a first subset of said optical detectors;

computing a b-vector for a second subset of said optical detectors; and

summing said two b-vectors.

15. The method of claim 11, wherein said processing of said plurality of sampled electrical signals includes the step of computing a first b-vector at a first time and computing a second b-vector at a second time and summing said two b-vectors.

16. The method of claim 11, wherein said processing of said plurality of sampled electrical signals includes:

computing a first b-vector from two sets of sampled electrical signals separated by a time interval T1; and

computing a second b-vector from two sets of sampled electrical signals separated by a time interval T2, where T1 is not equal to T2.

17. The method of claim 11, wherein said processing of said plurality of sampled electrical signals includes:

defining the signals from a first discrete time as a reference set of signals computing distance moved since said reference set of signals; and

updating said reference set when said distance moved exceeds a predefined threshold.

18. The method of claim 11, wherein said processing of said plurality of sampled electrical signals includes:

computing distance moved at a plurality of discrete times;

replacing a value of said distance moved if the difference between the computed value of said distance moved differs from the values computed for other times within said plurality by more than a specified amount.

19. The method of claim 11, wherein said processing of said plurality of sampled electrical signals includes reporting no motion if the magnitude of one or more or a combination of said electrical signals falls below a predefined threshold.

20. The method of claim 19, wherein said processing of said plurality of sampled electrical signals includes:

computing a plurality of b-vectors for a plurality of discrete times;

summing said b-vectors to form a resultant b-vector; and

reporting no motion if the magnitude of said resultant b-vector falls below a predefined threshold.