PROXIMITY SENSOR AND PROXIMITY SENSING METHOD
First Claim
1. A proximity sensor, comprising:
- a sense electrode having a first capacitance to ground, wherein the first capacitance varies in response to proximity of an object to be sensed;
a first sense circuit which provides a first pulse signal having a pulse width determined in accordance with said first capacitance;
a reference capacitor;
a second sense circuit which provides a second pulse signal having a pulse width determined in accordance with a second capacitance of said reference capacitors; and
a computing circuit which computes a difference pulse width by subtracting said second pulse signal from said first pulse signal and provides a pulse having said difference pulse width.
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Abstract
A proximity sensor includes a sense electrode having a first capacitance to ground, wherein the first capacitance varies in response to proximity of an object to be sensed; a first sense circuit which provides a first pulse signal having a pulse width determined in accordance with the first capacitance; a reference capacitor; a second sense circuit which provides a second pulse signal having a pulse width determined in accordance with a second capacitance of the reference capacitor; and a computing circuit which computes a difference pulse by subtracting the second pulse signal from the first pulse signal and provide a pulse of the difference pulse width.
29 Citations
17 Claims
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1. A proximity sensor, comprising:
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a sense electrode having a first capacitance to ground, wherein the first capacitance varies in response to proximity of an object to be sensed; a first sense circuit which provides a first pulse signal having a pulse width determined in accordance with said first capacitance; a reference capacitor; a second sense circuit which provides a second pulse signal having a pulse width determined in accordance with a second capacitance of said reference capacitors; and a computing circuit which computes a difference pulse width by subtracting said second pulse signal from said first pulse signal and provides a pulse having said difference pulse width. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A proximity sensor, comprising:
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a sense electrode having a first capacitance to ground, wherein said first capacitance varies in response to proximity of an object to be sensed; a first sense circuit which provides a first pulse signal having a pulse width determined in accordance with said first capacitance; a reference electrode; a second sense circuit which provides a second pulse signal having a pulse width determined in accordance with a second capacitance between said reference electrode and ground; and a computing circuit which computes a difference pulse width by subtracting said second pulse signal from said first pulse signal and provides a pulse having said difference pulse width. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. A proximity sensing method, comprising:
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receiving a first pulse signal having a first pulse width determined in accordance with a first capacitance between a sense electrode and ground, wherein said first capacitance varies in response to proximity of an object to be sensed and ground to measure said first pulse width; receiving a second pulse signal having a second pulse width determined in accordance with a second capacitance of a reference capacitor to measure said second pulse width; and computing a difference pulse by subtracting said second pulse width of said second pulse signal from said first pulse width of said first pulse signal and providing a pulse of said difference pulse width.
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17. A proximity sensing method, comprising:
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receiving a first pulse signal having a first pulse width determined in accordance with a first capacitance between a sense electrode and ground, wherein said first capacitance is variable in response to proximity of an object to be sensed and ground to measure said first pulse width; receiving a second pulse signal having a second pulse width determined in accordance with a second capacitance between a reference electrode and ground to measure said second pulse width; and computing a difference pulse by subtracting said second pulse width of said second pulse signal from said first pulse width of said first pulse signal and providing a pulse of said difference pulse width.
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Specification