Object sensing
First Claim
1. An object sensing system, comprising:
- (i) a first electric field sensing transmission electrode;
(ii) an electric field sensing reception electrode;
(iii) a driving circuit for driving the first electric field sensing transmission electrode so as to generate a first electric field;
(iv) an electric field generating object comprising;
(a) a second electric field sensing transmission electrode, and (b) means for driving the second electric field sensing transmission electrode so as to generate a second electric field; and
(v) a current sensing circuit for distinguishably sensing currents induced in the electric field sensing reception electrode by the first electric field and the second electric field;
wherein the first electric field sensing transmission electrode and the electric field sensing reception electrode are arranged such that a first object placed in the vicinity of the first electric field sensing transmission electrode and the electric field sensing reception electrode causes a variation in the current induced in the electric field sensing reception electrode by the first electric field; and
the current sensing circuit is adapted to sense the first object from the variation in the current induced in the electric field sensing reception electrode by the first electric field and to sense the electric field generating object from a variation in the current induced in the electric field sensing reception electrode by the second electric field.
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Accused Products
Abstract
A combined passive and active object sensing system (30; 50; 70) employing electric field sensing is described. An electric field sensing transmission electrode (2) generates a first electric field (11, 12, 13) that induces a current in an electric field sensing reception electrode (4). A passive object (10) is sensed from variation in this current. An active object (31; 51; 71) comprises a further electric field sensing transmission electrode (33; 53; 73) and generates a second electric field (35, 36, 37; 55, 56, 57; 75, 76, 77). This may be generated by the active object (31) coupling with and applying a phase shift to the first electric field (11, 12, 13). Alternatively the second electric field (55, 56, 57) may be generated at a different frequency to the first electric field (11, 12, 13). Alternatively the second electric field (75, 76, 77) may be generated by the active object (71) coupling with an alternating magnetic field generated by a coil (172). The second electric field (35, 36, 37; 55, 56, 57; 75, 76, 77) induces a current in the electric field sensing reception electrode (4) that varies with the position of the active object (31; 51; 71). The separate currents are distinguished by virtue of their different phase or frequency.
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Citations
18 Claims
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1. An object sensing system, comprising:
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(i) a first electric field sensing transmission electrode;
(ii) an electric field sensing reception electrode;
(iii) a driving circuit for driving the first electric field sensing transmission electrode so as to generate a first electric field;
(iv) an electric field generating object comprising;
(a) a second electric field sensing transmission electrode, and (b) means for driving the second electric field sensing transmission electrode so as to generate a second electric field; and
(v) a current sensing circuit for distinguishably sensing currents induced in the electric field sensing reception electrode by the first electric field and the second electric field;
wherein the first electric field sensing transmission electrode and the electric field sensing reception electrode are arranged such that a first object placed in the vicinity of the first electric field sensing transmission electrode and the electric field sensing reception electrode causes a variation in the current induced in the electric field sensing reception electrode by the first electric field; and
the current sensing circuit is adapted to sense the first object from the variation in the current induced in the electric field sensing reception electrode by the first electric field and to sense the electric field generating object from a variation in the current induced in the electric field sensing reception electrode by the second electric field. - View Dependent Claims (2, 3, 4, 5, 15, 16, 17, 18)
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6. An active tag, comprising:
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an electric field sensing transmission electrode; and
a reception electrode for coupling with a first electric field to generate a received signal;
means for applying a phase shift to the received signal; and
means for driving the electric field sensing transmission electrode with the phase shifted signal so as to generate a second electric field. - View Dependent Claims (7)
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8. A set of active tags, each tag comprising:
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an electric field sensing transmission electrode; and
means for driving the electric field sensing transmission electrode so as to generate an electric field of a given frequency for each tag;
wherein the given frequency for each of at least some of the tags is different.
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9. A current sensing circuit for an electric field sensing arrangement;
- the current sensing circuit comprising;
means for sensing variation in a current induced in an electric field sensing reception electrode by a first electric field; and
means for separately sensing variation in a current induced in the electric field sensing reception electrode by a second electric field. - View Dependent Claims (10, 11, 12, 13)
- the current sensing circuit comprising;
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14. A method of sensing objects, comprising:
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generating a first electric field using a first electric field sensing transmission electrode;
sensing a first current induced in an electric field sensing reception electrode by the first electric field;
sensing a first object by detecting variation in the current induced by the first electric field, the variation being caused by the first object being placed in the vicinity of the first electric field sensing transmission electrode and the electric field sensing reception electrode;
generating a second electric field using an electric field sensing transmission electrode located in a second object;
sensing the second object by sensing, in distinction from the first current, a second current induced in the electric field sensing reception electrode by the second electric field when the second object is placed in the vicinity of the electric field sensing reception electrode.
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Specification