Method and Algorithm for Accurate Finger Motion Tracking

• US 20080219521A1
• Filed: 12/14/2007
• Published: 09/11/2008
• Est. Priority Date: 04/16/2004
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Validity Sensors Incorporated (Synaptics Incorporated)
• Inventors: Satyan, Pallavi, Geoffroy, David Joseph, BENKLEY, FRED GEORGE
• Granted Patent: US 8,229,184 B2
• Time in Patent Office: Days
• US Class Current: 382/124
• CPC Class Codes: G06V 40/1335 Combining adjacent partial images (e.g. slices) to create a composite input or reference pattern; Tracking a sweeping finger movement

Abstract

Enhanced accuracy finger position and motion sensors devices, algorithms, and methods are disclosed that can be used in a variety of different applications. The sensors can be used in conjunction with partial fingerprint imagers to produce improved fingerprint scanners. The finger motion sensors may also be used (either with or without a partial fingerprint imager) to produce highly accurate fingerprint images as well as to control electronic devices. Here improved signal analysis algorithms and methods are disclosed that enable finger position to be determined with higher levels of accuracy as the finger is swiped over finger position sensing arrays. These algorithms are particularly useful for deep finger penetrating radio frequency (RF) based sensing arrays.

Claims

1. A method for determining the motion or position of an object moving proximate a sensing array composed of multiple detection elements separated by multiple gaps between said elements, said method comprising:

Repeatedly performing the steps of;

A. monitoring the signal generated by said detection elements and detecting when the noise level of said signal is less than a first preset noise criteria for a first preset period of time;

B. setting the commencement time of a stable signal when said first preset noise criteria and said first preset period of time are met;

C. continuing to monitor the signal generated by said detection elements and detecting when the noise level of said signal exceeds a second preset noise criteria for a second preset period of time;

D. setting the termination time of a stable signal when said second preset noise criteria and said second preset period of time are met;

E. calculating a designated stable time that is in between said commencement time and said termination time; and

then returning to step A and repeating the steps;

wherein the time elapsed between the time of a second designated stable time performed in a later repetition of steps A through E and the time of a first designated stable time performed in an earlier repetition of steps A though E is computed and is used to determine either the motion or position of said object.

2. The method of claim 1, in which the object is a finger

3. The method of claim 1, in which the sensing array is a finger sensing array.

4. The method of claim 1, in which the object is a finger, the sensing array is a finger sensing array, and the method is used in conjunction with partial fingerprint images of said finger to assist in assembly of said partial fingerprint images into a complete fingerprint image.

5. The method of claim 1, in which the object is a finger, the sensing array is a finger sensing array, and the method is used for the control of an electrical device.

6. The method of claim 1, in which the sensing array is a deep finger penetrating radio frequency (RF) based sensing array.

7. The method of claim 1, in which the sensing array is an optical sensing array.

8. The method of claim 1, in which the motion or location of said object in two dimensions is determined by combining data from multiple sensing arrays, and in which at least one of said multiple sensing arrays operates according to the method of claim 1.

9. The method of claim 1, in which the designated stable time is midway between said commencement time and said termination time, and in which said designated stable time is computed by calculating the average of said commencement time and said termination time.

17. The method of claim 16, in which the motion or location of said finger in two dimensions is determined by combining data from multiple sensing arrays, and in which at least one of said multiple sensing arrays operates according to the method of claim 1.

18. The method of claim 17, in which the motion of said finger is used to control a cursor or a menu on the display screen of a microprocessor or computer controlled device.

10. A method for determining the motion or position of a finger moving proximate an electrical sensing array composed of multiple detection elements separated by multiple gaps between said elements, said method comprising:

Repeatedly performing the steps of;

A. monitoring the signal generated by said detection elements and detecting when the noise level of said signal is less than a first preset noise criteria for a first preset period of time;

B. setting the commencement time of a stable signal when said first preset noise criteria and said first preset period of time are met;

C. continuing to monitor the signal generated by said detection elements and detecting when the noise level of said signal exceeds a second preset noise criteria for a second preset period of time;

D. setting the termination time of a stable signal when said second preset noise criteria and said second preset period of time are met;

E. calculating a designated stable time that is in between said commencement time and said termination time; and

then returning to step A and repeating the steps;

wherein the time elapsed between the time of a second designated stable time performed in a later repetition of steps A through E and the time of a first designated stable time performed in an earlier repetition of steps A though E is computed and is used to determine either the motion or position of said finger.

11. The method of claim 10, wherein said electrical sensing array is a deep finger penetrating radio frequency (RF) based sensing array.

12. The method of claim 10, wherein a partial fingerprint imager is disposed proximate said sensing array, and in which said partial fingerprint imager captures multiple images of the fingerprint of said finger as it moves proximate to said sensing array.

13. The method of claim 12, wherein if the finger motion data indicates that the finger motion has exceeded a preset limit, thus producing gaps between said multiple images of the fingerprint of said finger, these gaps are corrected by interpolating between said multiple images.

14. The method of claim 12, wherein if the finger motion data indicates that the finger motion is less than a preset limit, thus producing redundant multiple images that image the substantially same region of said fingerprint of said finger, then these redundant images are removed.

15. The method of claim 12, in which the fingerprint of said finger is compared to an authorized fingerprint and the results of this comparison used for security access purposes.

16. The method of claim 10, in which the movement of the finger is used for the control of an electrical device.

19. The method of claim 10, in which the electrical device is an electrical device selected from the group consisting of cellular telephones, smart cards, laptop computers, personal digital accessories, digital cameras, radios, memory storage devices, digital music players, or personal computers.

20. The method of claim 19, in which the electrical sensing array is a deep finger penetrating radio frequency (RF) based sensing array.

21. A method for determining the motion or position of an object moving proximate a sensing array composed of multiple detection elements separated by multiple gaps between said elements, said method comprising:

monitoring the signal generated by said detection elements and detecting when the noise level of said signal is less than a first preset noise criteria for a first preset period of time;

setting the commencement time of a stable signal when said first preset noise criteria and said first preset period of time are met;

continuing to monitor the signal generated by said detection elements and detecting when the noise level of said signal exceeds a second preset noise criteria for a second preset period of time;

setting the termination time of a stable signal when said second preset noise criteria and said second preset period of time are met;

calculating a designated stable time that is in between said commencement time and said termination time; and

then returning to step A and rep eating the steps;

wherein the time elapsed between the time of a second designated stable time performed in a later repetition of one or more of the steps and the time of a first designated stable time performed in an earlier repetition of one or more of the steps is computed and is used to determine either the motion or position of said object.