US 6,661,410 B2 · Capacitive sensing and data input device power management

Abstract

Capacitive proximity sensing is carried out by detecting a relative change in the capacitance of a “scoop” capacitor formed by a conductor and a surrounding ground plane. The conductor may be a plate provided in the form of an adhesive label printed with conductive ink. Charge is transferred between the “scoop” capacitor and a relatively large “bucket” capacitor, and a voltage of the bucket capacitor is applied to an input threshold switch. A state transition (e.g., from low to high, or high to low) of the input threshold switch is detected and a value (TouchVal) indicative of a number of cycles of charge transfer required to reach the state transition is determined. The presence or absence of an object or body portion in close proximity to or contact with a device can be determined by comparing TouchVal with a predetermined threshold value (TouchOff). TouchOff can be adjusted to take into account environmentally induced (non-touch related) changes in the capacitance of the scoop capacitor. Power management is provided in a user operated data input device utilizing proximity sensing and switching between three or more power states. Switching between the power states occurs based upon the presence or absence of input activity, and an operation instrumentality (e.g., a hand) in close proximity to or contact with the device. In an optical surface tracking cursor control device embodiment, switching to and from a BEACON state, which provides a reduced flash rate of a surface illuminating light source, is carried out based upon a detected presence or absence of a trackable surface.

Claims52

Dependent claims

A capacitive sensing system for sensing the presence of an object or body portion in contact with or close proximity to another object, comprising:

a first conductor capacitively coupled to a ground to thereby form a scoop capacitor having a capacitance which varies in relation to the proximity of said object or body portion to said conductor;
a pair of second and third conductors forming a bucket capacitor having a capacitance which is larger than a maximum capacitance of said scoop capacitor;
an input threshold switch;
switching means for selectively:
connecting at least one of said scoop capacitor and bucket capacitor to a voltage source to charge said at least one capacitor, varying the charge of said bucket capacitor in relation to a relative size of said scoop capacitor, said varying being carried out for plural cycles of charge transfer to or from said scoop capacitor, and applying a voltage of said bucket capacitor to said input threshold switch;
detector means for detecting an input state of said input threshold switch;
determining means for determining a value (TouchVal) based upon a count of a number of said cycles of charge transfer corresponding to a detection of a transition of said input threshold switch by said detector means;
and
signal generating means for generating, based upon TouchVal, a signal indicative of an ON state wherein said object or body portion is in contact with or close proximity to said another object, and an OFF state wherein said object or body portion is not in contact with or close proximity to said another object.

6 more elements

A method for sensing the presence of an object or body portion in contact with or close proximity to another object, comprising:

providing a first conductor capacitively coupled to a ground to thereby form a scoop capacitor having a capacitance which varies in relation to the proximity of said object or body portion to said conductor;
a pair of second and third conductors forming a bucket capacitor having a capacitance which is larger than a maximum capacitance of said scoop capacitor;
and an input threshold switch;
performing switching to selectively:
connect at least one of said scoop capacitor and said bucket capacitor to a voltage source to charge said at least one capacitor, vary the charge of said bucket capacitor in relation to a relative size of said scoop capacitor, said varying being carried out for plural cycles of charge transfer to or from said scoop capacitor, and apply a voltage of said bucket capacitor to said input threshold switch;
detecting an input state of said input threshold switch;
determining a value (TouchVal) relating to a number of said cycles of charge transfer corresponding to a detection of a transition of said input threshold switch;
and
generating, based upon TouchVal, a signal indicative of an ON state wherein said object or body portion is in contact with or close proximity to said another object, and an OFF state wherein said object or body portion is not in contact with or close proximity to said object.

6 more elements

A capacitive sensing system for sensing the presence of an object or body portion in contact with or close proximity to another object, comprising:

a first conductor capacitively coupled to a ground to thereby form a scoop capacitor having a capacitance which varies in relation to the proximity of said object or body portion to said conductor;
a pair of second and third conductors forming a bucket capacitor having a capacitance which is larger than a maximum capacitance of said scoop capacitor;
an input threshold switch;
switching means for selectively:
connecting at least one of said scoop capacitor and bucket capacitor to a voltage source to charge said at least one capacitor, varying the charge of said bucket capacitor in relation to a relative size of said scoop capacitor, and applying a voltage of said bucket capacitor to said input threshold switch;
detector means for detecting an input state of said input threshold switch;
determining means for determining a value (TouchVal) relating to a number of cycles of said varying of the bucket capacitor charge, corresponding to a detection of a transition of said input threshold switch by said detector means;
signal generating means for generating, based upon TouchVal, a signal indicative of an ON state wherein said object or body portion is in contact with or close proximity to said another object, and an OFF state wherein said object or body portion is not in contact with or close proximity to said another object;
comparing means for comparing TouchVal, or a number derived from TouchVal, with a predetermined threshold value (TouchOff), or a number derived from TouchOff;
and wherein said signal generating means generates said ON and OFF state indicating signals based upon an output of said comparing means;
and
threshold count determining means for dynamically adjusting the value of TouchOff in accordance with a relative decrease in the capacitance of said scoop capacitor occurring during said OFF state.

9 more elements

Dependencies are inferred from the claim text.

Capacitive sensing and data input device power management

Life of this patent

Capacitive sensing and data input device power management

Life of this patent

Abstract

Claims52