System and method for detecting and characterizing touch inputs at a human-computer interface

1. A system for detecting inputs at a computing device comprising:

a substrate comprising:

a top layer; and

a bottom layer defining a first support location;

an first set of drive and sense electrode pairs arranged across the top layer of the substrate;

a first sense electrode arranged proximal the first support location on the bottom layer of the substrate;

a touch sensor surface arranged over the substrate;

a first spring element:

coupled to the substrate at the first support location; and

configured to couple the substrate to a chassis and to yield to downward displacement of the substrate, toward the chassis, responsive to forces applied to the touch sensor surface; and

a coupling layer:

arranged below the substrate; and

defining a first coupling region adjacent the first support location and configured to effect electrical values of the first sense electrode responsive to displacement of the substrate toward the coupling layer.

2. The system of claim 1 , further comprising a controller configured to:

read a first set of electrical values from the first set of drive and sense electrode pairs;

interpret a first touch input at a first location on the touch sensor surface based on the first set of electrical values;

read a second set of electrical values from the first sense electrode; and

interpret a first force magnitude of the first touch input based on the first set of electrical values.

3. The system of claim 1 , further comprising a second set of drive and sense electrode pairs:

comprising the first sense electrode;

arranged across a bottom layer of the substrate; and

configured to capacitively couple a set of coupling regions of the coupling layer to form a set of force sensors below the substrate.

4. The system of claim 3 , further comprising a controller configured to:

read a first set of capacitance values between drive electrodes and sense electrodes in the first set of drive and sense electrode pairs;

read a second set of capacitance values between drive electrodes and sense electrodes in the set of force sensors;

detect a lateral position and a longitudinal position of a touch input on the touch sensor surface based on the first set of capacitance values;

interpret a force magnitude of the touch input based on the second set of capacitance values; and

output the lateral position, the longitudinal position, and the force magnitude.

5. The system of claim 1 :

wherein the coupling layer comprises a coupling plate:

interposed between the first spring element and the substrate;

comprising a first perforation aligned with the first support location and the first spring element;

defining the first coupling region adjacent the first perforation;

further comprising a first spacer element:

extending through the first perforation;

coupling the first support location on the bottom layer of the substrate to the first spring element; and

wherein the first sense electrode:

capacitively couples to the first coupling region, in the set of coupling regions, of the coupling plate; and

moves toward the first coupling region in response to application of a force on the touch sensor surface proximal the capacitance sensor.

6. The system of claim 1 :

wherein the first spring element:

is formed in a unitary structure arranged below the substrate and defining a nominal plane;

defining a first stage; and

configured to return to approximately the nominal plane in response to absence of a touch input applied to the touch sensor surface; and

further comprising a first spacer element coupling the first support location on the bottom layer of the substrate to the first stage of the first spring element.

7. The system of claim 6 :

wherein the first spring element yields to a touch input applied to a first region of the touch sensor surface proximal the first spring element;

wherein the first sense electrode advances toward the first coupling region by a distance proportional to a force magnitude of the touch input; and

further comprising a controller configured to:

detect a first change in capacitance value of the first sense electrode; and

interpret the force magnitude of the touch input based on the first change in capacitance value.

8. The system of claim 1 , further comprising a first spacer element:

interposed between the bottom layer of the substrate and the coupling layer; and

coupling the first support location to the first spring element.

9. The system of claim 1 , wherein the coupling layer defines a unitary structure comprising:

the first spring element arranged on the unitary structure opposite the first location; and

the first coupling region arranged proximal the first spring element on the unitary structure.

10. The system of claim 1 :

further comprising a second set of sense electrodes comprising the first sense electrode, each sense electrode in the second set of sense electrodes, encircling a set of support locations on the bottom layer of the substrate;

wherein the coupling layer defines a set of coupling regions comprising the first coupling region, each coupling region in the set of coupling regions arranged adjacent a support location in the set of support locations; and

further comprising a controller configured to:

read a set of capacitance values, from the second set of sense electrodes, representing measures of self-capacitance between the second set of sense electrodes and the set of coupling regions; and

interpret a distribution of forces applied to the touch sensor surface based on the set of capacitance values and spring constants of a set of spring elements arranged below the substrate.