OBJECT SENSING

WIPO Patent Application WO2003010486

A3

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.

VAN BERKEL CEES

PCT/IB2002/003160

November 20, 2003

July 22, 2002

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KONINKL PHILIPS ELECTRONICS NV (NL)

G01D5/24; G01V3/08; (IPC1-7): G01B7/00; G01V3/08; H03K17/955; G08B13/26

WO1994024645A1	1994-10-27
WO2000068044A1	2000-11-16
WO2000052657A1	2000-09-08

US6025726A

2000-02-15

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