Touch panel device and control method and device for eliminating noises in touch panel device

• US 20060214921A1
• Filed: 08/16/2005
• Published: 09/28/2006
• Est. Priority Date: 03/23/2005
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Takahashi, Yuji, Katsuki, Takashi, Sano, Satoshi, Nakazawa, Fumihiko
• Granted Patent: US 7,859,522 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0436 in which generating transducers and detecting transducers are attached to a single acoustic waves transmission substrate

Abstract

A touch panel device includes an excitation transducer for exciting a surface acoustic wave upon application of a burst wave and a reception transducer for receiving the surface acoustic wave and converting the same into a reception signal that are arranged at a peripheral portion of a detection area so that a position of an object touching the detection area is detected in accordance with a change in the reception signal. A control method for eliminating noises in the touch panel device includes the steps of detecting a differential between a reception signal due to a burst wave and another reception signal due to another burst wave, deciding that there is a noise if the detected differential exceeds a preset threshold value, and performing a control operation so that the detection of an object based on the reception signal is not performed in accordance with the decision.

Claims

1. A control method for eliminating noises in a touch panel device including an excitation transducer for exciting a surface acoustic wave upon application of a burst wave and a reception transducer for receiving the surface acoustic wave and converting the same into a reception signal that are arranged at a peripheral portion of a detection area so that a position of an object touching the detection area is detected in accordance with a change in the reception signal, the control method comprising the steps of:

detecting a differential between a reception signal due to a burst wave and another reception signal due to another burst wave;

deciding that there is a noise if the detected differential exceeds a preset threshold value; and

performing a control operation so that the detection of an object based on the reception signal is not performed in accordance with the decision.

2. The control method according to claim 1, wherein the differential detecting step includes detecting a differential between a reception signal at a time and a reception signal at a previous time.

3. The control method according to claim 1, further comprising the steps of stopping an application of the burst wave until a preset wait time passes if the detected differential exceeds the preset threshold value, and restarting the application of the burst wave after the wait time has passed.

4. The control method according to claim 1, further comprising the steps of deciding that there is a noise if a level of a noise floor exceeds a preset second threshold value in a period other than a period in which a reception signal due to the burst wave is obtained, and performing a control operation so that the detection of an object based on the reception signal is not performed in accordance with the decision.

5. The control method according to claim 1, further comprising the steps of stopping an application of the burst wave if a level of a noise floor exceeds a preset second threshold value until a preset wait time passes, and restarting the application of the burst wave after the wait time has passed.

6. A control device for eliminating noises in a touch panel device including an excitation transducer for exciting a surface acoustic wave upon application of a burst wave and a reception transducer for receiving the surface acoustic wave and converting the same into a reception signal that are arranged at a peripheral portion of a detection area so that a position of an object touching the detection area is detected in accordance with a change in the reception signal, the control device comprising:

a differential detecting portion for detecting a differential between a reception signal due to a burst wave and another reception signal due to another burst wave;

a noise detecting portion for detecting a noise when the detected differential exceeds a preset threshold value; and

a control portion for performing a control operation so that the detection of an object based on the reception signal is not performed when a noise is detected.

7. The control device according to claim 6, wherein the differential detecting portion detects a differential between a reception signal at a time and a reception signal at a previous time.

8. The control device according to claim 6, wherein the control portion performs a control operation to stop an application of the burst wave until a preset wait time passes when the noise detecting portion detects a noise, and to restart the application of the burst wave after the wait time has passed.

9. The control device according to claim 6, further comprising a second noise detecting portion for detecting a noise when a level of a noise floor exceeds a second threshold value in a period other than a period in which a reception signal due to the burst wave is obtained, wherein the control portion performs a control operation so that the detection of an object based on the reception signal is not performed when the second noise detecting portion detects a noise.

10. The control device according to claim 6, further comprising a count portion for counting the number of times when the detected differential exceeds the preset threshold value and a threshold change portion for changing the threshold value when a count value of the count portion exceeds a predetermined value.

11. A touch panel device including an excitation transducer for exciting a surface acoustic wave upon application of a burst wave and a reception transducer for receiving the surface acoustic wave and converting the same into a reception signal that are arranged at a peripheral portion of a detection area, the touch panel device comprising:

an oscillation portion for producing the burst wave plural times;

an A/D converter for converting the reception signal into digital reception data;

an object detecting portion for detecting a position of an object that touches the detection area by comparing the reception data with reference data stored in advance;

a differential detecting portion for detecting a differential between reception data due to a burst wave and another reception data due to another burst wave;

a noise detecting portion for detecting a noise when the detected differential exceeds a preset threshold value; and

a control portion for performing a control operation so that the detection of the object based on the reception data is not performed when a noise is detected.

12. The touch panel device according to claim 11, wherein the control portion performs a control operation so as to stop an application of the burst wave by the oscillation portion until a preset wait time passes when the noise detecting portion detects a noise and to restart the application of the burst wave after the wait time has passed.

13. The touch panel device according to claim 11, further comprising a smoothing portion for smoothing the reception data due to the burst waves of plural times so as to obtain average reception data.