Inductive Touch Sensor and Method for Operating the Same

Abstract

An inductive touch sensor including at least one magnetic field generating element for generating a magnetic field, at least one resonance element arranged in the magnetic field of the magnetic field generating element, a positioning element for positioning the at least one resonance element relative to the at least one magnetic field generating element, wherein the position of the resonance element relative to the at least one magnetic field generating element is adapted to be changed thereby changing the resonance generated in the resonance element by the magnetic field, an evaluation circuit for evaluating the change of the resonance of the resonance element such that thereby a detection of operation of the touch sensor is effected.

Claims

1. An inductive touch sensor comprising at least one magnetic field generating element for generating a magnetic field, at least one resonance element arranged in the magnetic field of the magnetic field generating element, a positioning element for positioning the at least one resonance element relative to the at least one magnetic field generating element, wherein the position of the resonance element relative to the at least one magnetic field generating element is adapted to be changed thereby changing the resonance generated in the resonance element by the magnetic field, and an evaluation circuit for evaluating the change of the resonance of the resonance element such that thereby a detection of operation of the touch sensor is effected.

2. The inductive touch sensor according to claim 1, wherein the magnetic field generating element is a coil.

3. The inductive touch sensor according to claim 2, wherein the resonance element is a capacitor.

4. The inductive touch sensor according to claim 1, wherein the positioning element comprises a resilient medium inside which the resonance element is arranged.

5. The inductive touch sensor according to claim 1, wherein, on a side of the inductive touch sensor touched by a user, a screening element is arranged.

6. The inductive touch sensor according to claim 1, wherein as an evaluation circuit a separate measuring branch of an excitation circuit is used to generate the magnetic field of the magnetic field generating element.

7. The inductive touch sensor according to claim 1, wherein the inductive touch sensor comprises at least two magnetic field generating elements, the at least two magnetic field generating elements excited at different frequencies, and, wherein the inductive touch sensor comprises at least two resonance elements.

8. A method for operating an inductive touch sensor according to claim 1, the method comprising: generating a magnetic field using at least one magnetic field generating element, measuring a changing resonance of at least one resonance element arranged in the magnetic field, wherein a position of the resonance element relative to the at least one magnetic field generating element is adapted to be changed thereby changing the resonance generated in the resonance element by the magnetic field, and evaluating the change of the resonance of the resonance element such that thereby a detection of operation of the inductive touch sensor is effected.

9. The method according to claim 8, further comprising: exciting at least two magnetic field generating elements at different frequencies, and measuring a resonance of at least two resonance elements arranged in the magnetic field, wherein a different resonating of the two resonator elements at the different frequencies indicates a position where the inductive touch sensor has been touched.

10. The inductive touch sensor according to claim 4, wherein the resilient medium comprises silicone.

Description

[0023] Hereunder preferred embodiments of the invention will be explained on the basis of the figures in which:

[0024] FIG. 1 shows a first embodiment of the touch sensor according to the invention,

[0025] FIGS. 2 and 3 show various operating modes of the touch sensor according to the invention.

[0026] As illustrated in FIG. 1, the inductive touch sensor 10 comprises a first coil (12a) and a second coil (12b) which respectively generate a magnetic field.

[0027] The resonator (14) is arranged in this common magnetic field not illustrated in FIG. 1. It is located in the resilient material 16 which may comprise a silicone material, for example, and which serves as a positioning element by means of which the resonator 14 is positioned relative to the coils 12a, 12b.

[0028] The side of the sensor 10 facing the outside is provided with a screening element 18.

[0029] If an object touches this screening element 18, the resilient medium 16 is compressed such that the distance of the resonator 14 relative to the coils 12a and/or 12b becomes smaller. Thereby the resonance generated in the resonator 14 by the magnetic field of the coils 12a, 12b changes. This change of the resonance is detected and evaluated by an evaluation circuit not illustrated such that it is possible to detect whether, and preferably at which location, the inductive touch sensor has been touched by the object.

[0030] FIG. 2 illustrates how a measuring sequence may be performed. In the middle of FIG. 2, the excitation is illustrated which is caused by a pulse and supplied to the two coils 12a, 12b by an excitation circuit not illustrated. Thereafter, the coils are immediately switched off. Due to the excitation a magnetic field is generated. This, in turn, results in the resonator 14 also being induced to resonate. This is illustrated in the right part of FIG. 2. When the coils 12a, 12b are switched off, a measuring circuit can measure the strength of the resonance field of the resonance element 14.

[0031] Another embodiment of the device according to the invention and the method according to the invention is shown in FIG. 3. Here, two coils 12a, 12b are used which are each excited at a different frequency. Furthermore, at least two resonator elements 14a, 14b are used which are arranged in the common magnetic field of the two coils. As can be seen in the lower part of FIG. 3, the two resonator elements respond in a different manner to the different frequencies.