Touch panel

• US 8,044,943 B2
• Filed: 06/03/2008
• Issued: 10/25/2011
• Est. Priority Date: 06/03/2008
• Status: Expired due to Fees

• Current Assignee: Himax Technologies Ltd. (Himax Technologies Incorporated)
• Original Assignee: Himax Technologies Ltd. (Himax Technologies Incorporated)
• Inventors: Chen, Ying-Lieh
• Primary Examiner(s): Lao; Lun-Yi
• Assistant Examiner(s): Tryder; Gregory J
• Application Number:
  US12/132,244
• Publication Number:
  US 20090295754A1
• Time in Patent Office: 1,239 Days
• Field of Search: 345/173, 345/175, 345/179, 345/182, 345/183, 345/207, 178/18.09, 178/19.05, 463/37
• US Class Current: 345/175
• CPC Class Codes: G06F 3/042 by opto-electronic means

Abstract

Touch panels comprising a bias line biased at a bias voltage, a select line, a readout line, a photo cell and a readout circuit. The photo cell comprises a first photo switch, a second photo switch and a storage capacitor. The first photo switch and the storage capacitor is coupled in series between the readout line and the bias line, and the first photo switch is further controlled by the select line. The second photo switch is connected between the readout line and the bias line. The readout circuit and the select line are managed by a reset mode, an exposure mode and a readout mode. The voltage variation of output terminal of the readout circuit is used in obtaining the state of the photo cell.

Claims

1. A touch panel, comprising:

a bias line, biased at a bias voltage;

a select line;

a readout line;

a photo cell, comprising;

a first photo TFT, having a first terminal, a second terminal and a control terminal, wherein the first terminal is coupled to the readout line and the control terminal is coupled to the select line;

a second photo TFT, having a first terminal, a second terminal and a control terminal, wherein the first terminal is coupled to the readout line, the second terminal and the control terminal are coupled to the bias line; and

a storage capacitor, coupling the second terminal of the first photo TFT to the bias line;

a readout circuit comprising;

an operational amplifier, having an inverting input terminal, a non-inverting input terminal and an output terminal, wherein the inverting input terminal is coupled to the readout line;

a feedback capacitor, coupled between the inverting input terminal and the output terminal of the operational amplifier; and

a first switch, coupled between the inverting input terminal and the output terminal of the operational amplifier, and

a multiplexer for selectively outputting a reference voltage or the bias voltage to the non-inverting input terminal.

2. The touch panel of claim 1, wherein, in a reset mode, the select line is asserted, the first switch is turned on, and the multiplexer outputs the reference voltage to the non-inverting input terminal.

3. The touch panel of claim 1, wherein, in an exposure mode, the select line is unasserted, the first switch is turned off, and the multiplexer outputs the bias voltage to the non-inverting input terminal.

4. The touch panel of claim 1, wherein, in a readout mode, the select line is asserted, the first switch is turned off, and the multiplexer outputs the reference voltage to the non-inverting input terminal of the operational amplifier, and a voltage of the output terminal of the operational amplifier is used in determining whether the touch panel is touched at the photo cell.

5. A touch panel, comprising:

a bias line;

a select line;

a readout line; and

a photo cell, comprising;

a storage capacitor;

a first photo TFT, having a first terminal, a second terminal and a control terminal, wherein the first terminal is coupled to the readout line, the second terminal is connected to the storage capacitor and the control terminal is coupled to the select line; and

a second photo TFT, having a first terminal, a second terminal and a control terminal, wherein the first terminal is coupled to the readout line, the second terminal and the control terminal are coupled to the bias line.

6. The touch panel of claim 5, wherein in a reset mode, the storage capacitor receives a reference voltage via the first photo switch while the select line is asserted;

wherein in a exposure mode, the select line is unasserted;

wherein in a readout mode, a voltage of the storage capacitor is read out via the first photo switch while the select line is asserted, to determine whether the photo cell is touched.

7. The touch panel of claim 6, further comprising a readout circuit, which is reset in the reset mode, and accumulates charges from the storage capacitor to determine whether the photo cell is touched.

8. The touch panel of claim 7, wherein the readout circuit comprises:

an operational amplifier, having an inverting input terminal, a non-inverting input terminal and an output terminal, wherein the inverting input terminal is coupled to the readout line;

a feedback capacitor, coupled between the inverting input terminal and the output terminal of the operational amplifier; and

a first switch, coupled between the inverting input terminal and the output terminal of the operational amplifier, and being turned on in the reset mode; and

a multiplexer for outputting a reference voltage to the non-inverting input terminal in the reset mode and the readout mode, and outputting the bias voltage to the non-inverting input terminal in the exposure mode.

9. The touch panel of claim 5, further comprising an image pixel corresponding to a data line and having a liquid crystal cell and a data switch, wherein the data switch is connected between the data line and the liquid crystal cell and is controlled by the select line.