Capacitance detection apparatus
First Claim
1. A capacitance detection apparatus for detecting an approach of an object on the basis of a change of capacitance, comprising:
- a detection electrode for detecting the change of the capacitance by approaching the object;
a calculating circuit for calculating a value associated with the change of the capacitance detected by the detection electrode;
a judging circuit for judging whether the value calculated by the calculating circuit is a normal value which is calculated after a predetermined period of time lapse from a start time of the capacitance detection apparatus or an initial value which is calculated before the predetermined period of time lapse from the start time of the capacitance detection apparatus;
an initial reference value-determining circuit for determining an initial reference value for the value judged by the judging circuit as the initial value;
a difference calculating circuit for calculating a difference between the value judged by the judging circuit as the normal value and a value calculated at a time earlier than a time when the value judged by the judging circuit as the normal value is calculated by the predetermined period of time or longer, or a difference between the value judged by the judging circuit as the initial value and the initial reference value determined by the initial reference value-determining circuit; and
a determining circuit for determining whether or not the object is approaching by comparing the difference calculated by the difference calculating circuit with a predetermined threshold value.
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Accused Products
Abstract
A capacitance detection apparatus includes a detection electrode for detecting approach of an object on the basis of a change of capacitance, a calculating circuit for calculating a value associated with the capacitance change, a judging circuit for judging whether the calculated value is a normal or initial value calculated after or before a predetermined period of time lapse from a start time of the capacitance detection apparatus, an initial reference value-determining circuit for determining an initial reference value, a difference calculating circuit for calculating a difference between the normal value and a value calculated earlier than a time when the normal value is calculated by the predetermined period of time or longer or between the initial value and the initial reference value, and a determining circuit for determining whether the object is approaching by comparing the difference with a predetermined threshold value.
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Citations
11 Claims
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1. A capacitance detection apparatus for detecting an approach of an object on the basis of a change of capacitance, comprising:
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a detection electrode for detecting the change of the capacitance by approaching the object; a calculating circuit for calculating a value associated with the change of the capacitance detected by the detection electrode; a judging circuit for judging whether the value calculated by the calculating circuit is a normal value which is calculated after a predetermined period of time lapse from a start time of the capacitance detection apparatus or an initial value which is calculated before the predetermined period of time lapse from the start time of the capacitance detection apparatus; an initial reference value-determining circuit for determining an initial reference value for the value judged by the judging circuit as the initial value; a difference calculating circuit for calculating a difference between the value judged by the judging circuit as the normal value and a value calculated at a time earlier than a time when the value judged by the judging circuit as the normal value is calculated by the predetermined period of time or longer, or a difference between the value judged by the judging circuit as the initial value and the initial reference value determined by the initial reference value-determining circuit; and a determining circuit for determining whether or not the object is approaching by comparing the difference calculated by the difference calculating circuit with a predetermined threshold value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification