System for detecting and characterizing inputs on a touch sensor

1. A method for detecting and characterizing inputs comprising:

during a first scan cycle:

reading a first set of force values from an array of sense electrodes supporting a touch sensor surface;

detecting a first input on the touch sensor surface;

interpreting a first geometry dimension of the first input;

interpreting a first force magnitude of the first input based on the first set of force values;

in response to the first geometry dimension of the first input remaining below a first threshold, and in response to a first ratio of the first force magnitude of the first input to the first geometry dimension of the first input exceeding a second threshold, characterizing the first input as a finger input type; and

recording a first location and a first input type of the first force input;

during a second scan cycle:

reading a second set of force values from the array of sense electrodes;

detecting a second input on the touch sensor surface;

interpreting a second geometry dimension of the second input;

interpreting a second force magnitude of the second input based on the second set of force values; and

in response to the second geometry dimension of the second input remaining below the first threshold, and in response to a second ratio of the second force magnitude of the second input to the second geometry dimension of the second input falling below the second threshold, characterizing the second input as a non-finger input type; and

recording a second location and a second input type of the second input.

2. The method of claim 1 , further comprising, during a third scan cycle:

reading a third set of force values from the array of sense electrodes;

detecting a third input on the touch sensor surface;

interpreting a third geometry dimension of the third input;

interpreting a third force magnitude of the third input based on the third set of force values;

in response to the third geometry dimension of the third input exceeding the first threshold, characterizing the third input as the non-finger input type; and

recording a third location and a third input type of the third force input.

3. The method of claim 2 :

further comprising, during the third scan cycle:

calculating a first best-fit boundary encompassing the third input on the touch sensor surface; and

extracting the third geometry dimension from the first best-fit boundary of the third input;

wherein extracting the third geometry dimension from the first best-fit boundary comprises extracting a first length of a major axis of the first best-fit boundary defining a first best-fit ellipse for the third geometry dimension; and

wherein characterizing the third input as the non-finger input type in response to the third geometry dimension of the third input exceeding the first threshold comprises characterizing the third input as the non-finger input type in response to the first geometry dimension of the first best-fit ellipse exceeding the first threshold.

4. The method of claim 2 :

further comprising extracting the third geometry dimension of the third input representing a width of the third input; and

wherein characterizing the third force input as the non-finger input type in response to the third geometry dimension exceeding the first threshold comprises characterizing the third input as a palm input type in response to the first geometry dimension exceeding the first threshold.

5. The method of claim 2 , further comprising, in response to the third geometry dimension of the third input remaining above the first threshold following the first scan cycle, during a fourth scan cycle:

reading a fourth set of force values from an array of sense electrodes;

detecting a fourth input on the touch sensor surface proximal the third input;

interpreting a fourth geometry dimension of the fourth input;

interpreting a fourth force magnitude of the fourth input based on the fourth set of force values; and

in response to the fourth geometry dimension of the fourth force input exceeding a third threshold less than the first threshold, characterizing the fourth force input as a non-finger type.

6. The method of claim 2 , further comprising, during a fourth scan cycle, succeeding the third scan cycle:

accessing the third location of the third input;

reading a fourth set of force values from an array of sense electrodes;

detecting a fourth input at a fourth location remote from the third location on the touch sensor surface;

interpreting a fourth geometry dimension of the fourth input;

interpreting a fourth force magnitude of the fourth input based on the fourth set of force values; and

response to the fourth geometry dimension of the fourth force input falling below a third threshold, characterizing the fourth force input as a finger input type.

7. The method of claim 1 , further comprising, during a third scan cycle, succeeding the first scan cycle:

accessing the first location of the first input;

reading a third set of force values from the array of sense electrodes;

detecting a third input at a third location proximal the first location on the touch sensor surface;

interpreting a third force magnitude of the third input based on the third set of force values;

in response to a third ratio of the third force magnitude of the third input to a third geometry dimension of the third input exceeding the second threshold:

characterizing the third input as the finger input type; and

in response to a first distance between the first input and the third input falling within a threshold distance, confirming the first input as the finger input type.

8. The method of claim 1 , further comprising, during a third scan cycle, succeeding the first scan cycle:

accessing the second location of the second input;

reading a third set of force values from the array of sense electrodes;

detecting a third input at a third location proximal the second location on the touch sensor surface;

interpreting a third force magnitude of the third input based on the third set of force values; and

in response to a third ratio of the third force magnitude of the third input to a third geometry dimension of the third input falling below the second threshold:

characterizing the third input as the non-finger input type; and

in response to a first distance between the second input and the third input falling within a threshold distance, confirming the second input as the non-finger input type.

9. The method of claim 1 , wherein characterizing the first input as a finger input type further comprises:

calculating a first score for the first geometry dimension based on a probability that the first geometry dimension associated with the first input represents the finger input type;

calculating a first confidence score representing a combination of the first score and the first ratio;

in response to the first confidence score exceeding a high score threshold, characterizing the first force input as the finger input type; and

in response to the first confidence score exceeding a low score threshold and falling below the high score threshold, characterizing the first force input as a low confidence finger input type.

10. The method of claim 9 , further comprising, in response to characterizing the first force input as the low confidence finger input type:

detecting a third input proximal the first input;

calculating a second score for a third geometry dimension of the third force input;

calculating a second confidence score representing a combination of the third score and a third ratio of the third force magnitude of the third input to the third geometry dimension of the third force;

in response to the second confidence score exceeding the high score threshold, characterizing the first input and the third input as the finger input type; and

in response to the second confidence score falling below the low score threshold, characterizing the first force input and the third force input as the non-finger input type.

11. The method of claim 1 , further comprising, during a third scan cycle, succeeding the first scan cycle:

accessing the first location of the first input;

reading a third set of force values from the array of sense electrodes;

detecting a third input at a third location proximal the first location on the touch sensor surface;

interpreting a third geometry dimension of the third input;

interpreting a third force magnitude of the third input based on the third set of force values; and

in response to a first distance between the first location and the third location exceeding a threshold distance, characterizing the third input as the non-finger input type.

12. The method of claim 1 :

further comprising, during the first scan cycle:

scanning the array of sense electrodes at a first resolution to generate the first set of force values from rows and columns of sense electrodes;

interpolating between force values in the first set of force values to generate a first set of interpolated force values;

compiling the first set of force values and the set of interpolated force values to generate a first force image;

defining a contiguous boundary encompassing a first contiguous cluster of force values in the first force image; and

calculating the first geometric dimension as a function of an area encompassed by the contiguous boundary; and

wherein detecting the first input on the touch sensor surface comprises interpreting the first contiguous cluster of force values in the first force image exceeding a minimum force threshold as the first input.

13. The method of claim 1 , further comprising, during the first scan cycle:

calculating a first best-fit boundary encompassing the first input on the touch sensor surface; and

extracting the first geometry dimension from the first best-fit boundary of the first input.

14. The method of claim 13 :

wherein extracting the first geometry dimension from the first best-fit boundary comprises extracting a first length of a major axis of the first best-fit boundary defining a first best-fit ellipse; and

wherein characterizing the first input as a finger input type in response to the first geometry dimension of the first input falling below the first threshold comprises characterizing the first input as the finger input type in response to the first geometry dimension of the first best-fit ellipse falling below the first threshold.

15. The method of claim 14 :

further comprising, during the first scan cycle:

extracting a second length of a minor axis of the first best-fit ellipse; and

calculating a first area of the first best-fit ellipse based on the first length of the major axis and the second length of the minor axis; and

wherein characterizing the first input as the finger type input, in response to the first geometry dimension of the first input falling below the first threshold, comprises:

calculating the first ratio of the first force magnitude of the first input to the first area of the first best-fit ellipse; and

in response to the first ratio of the first force magnitude of the first input to the first area of the first best-fit ellipse exceeding the second threshold, characterizing the first input as the finger input type.

16. A method for detecting and characterizing inputs comprising:

during a first scan cycle:

reading a first set of force values from an array of sense electrodes supporting a touch sensor surface;

detecting a first input at a first location on the touch sensor surface;

interpreting a first force magnitude of the first input based on the first set of force values;

in response to a first ratio of the first force magnitude of the first input to a first geometry dimension of the first input exceeding a first threshold, characterizing the first input as a finger input type; and

recording the first location and a first input type of the first input; and

during a second scan cycle, succeeding the first scan cycle:

reading a second set of force values from the array of sense electrodes;

detecting a second input at a second location proximal the first location on the touch sensor surface;

interpreting a second force magnitude of the second input based on the second set of force values;

in response to a second ratio of the second force magnitude of the second input to a second geometry dimension of the second input exceeding the first threshold:

characterizing the second input as the finger input type; and

in response to a first distance between the first input and the second input falling within a first threshold distance, confirming the first input as the finger input type; and

recording the second location and a second input type of the second input.

17. The method of claim 16 , further comprising, during a third scan cycle:

reading a third set of force values from the array of sense electrodes;

detecting a third input at a third location on the touch sensor surface;

interpreting a third force magnitude of the third input based on the third set of force values;

in response to a third ratio of the third force magnitude of the third input to a third geometry dimension of the third input falling below the first threshold, characterizing the third input as a non-finger input type; and

recording the third location and a third input type of the third input.

18. The method of claim 17 , further comprising, during a fourth scan cycle, succeeding the third scan cycle:

accessing the third location of the third input;

reading a fourth set of force values from the array of sense electrodes;

detecting a fourth input at a fourth location proximal the third location on the touch sensor surface;

interpreting a fourth force magnitude of the fourth input based on the fourth set of force values; and

in response to a fourth ratio of the fourth force magnitude of the fourth input to a fourth geometry dimension of the fourth input falling below the first threshold:

characterizing the fourth input as the non-finger input type; and

in response to a second distance between the third input and the fourth input falling within a second threshold distance, confirming the third input as the non-finger input type.