Flat Panel Display with Capacitance Sensing Touch Screen

• US 20100110035A1
• Filed: 11/05/2008
• Published: 05/06/2010
• Est. Priority Date: 11/05/2008
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Selker, Edwin Joseph
• Granted Patent: US 8,373,667 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G09G 5/003 Details of a display terminal, the details relating to the control arrangement of the display terminal and to the interfaces thereto specific for a CRT G09G1/165; for a flat panel G09G3/2092

Abstract

There is disclosed a display device with an integral touch screen. A display panel includes a plurality of pixels controlled by a plurality of column electrodes and a plurality of row electrodes. A column driver having a plurality of outputs drives the plurality of column electrodes, and a row driver having a plurality of outputs drives the plurality of row electrodes. A column sensor and a row sensor sense capacitive coupling between the row and column electrodes and a probe adjacent to an external surface of the display panel.

Claims

1. A display device with an integral touch screen, comprising:

a display panel comprising a plurality of pixels, a plurality of column electrodes, and a plurality of row electrodes, each pixel controlled by a corresponding one of the plurality of column electrodes and a corresponding one of the plurality of row electrodes

a column driver having respective column driver circuits for driving each of the plurality of column electrodes

a column sensor including column sensing circuits adapted to sense capacitive coupling between at least some of the plurality of column electrodes and a probe adjacent to an external surface of the display panel

a row driver having respective row driver circuits for driving each of the plurality of row electrodes a row sensor including row sensing circuits adapted to sense capacitive coupling between at least some of the plurality of row electrodes and the probe.

2. The display device of claim 1, wherein the column sensing circuits and the row sensing circuits sense the capacitive coupling to the probe by detecting one of a current flow in to the respective column and row electrodes and a voltage coupled to the respective column and row electrodes.

3. The display device of claim 2, wherein

the probe is grounded

the column sensing circuits and the row sensing circuits sense the capacitive coupling to the probe by detecting a current flow in the respective column and row electrodes.

4. The display device of claim 2, wherein

the probe is connect to an AC voltage source

the column sensing circuits and the row sensing circuits sense the capacitive coupling to the probe by detecting a coupled AC voltage in the respective column and row electrodes.

5. The display device of claim 4, wherein

the AC voltage source has predetermined frequency

the column sensing circuits and the row sensing circuits include filters selective for the predetermined frequency.

6. The display device of claim 4, wherein

the row driver and the column driver cyclically write image data to the display panel

the column sensing circuits and the row sensing circuits detect a coupled AC voltage during a sensing interval within at least some of the writing cycles.

7. The display device of claim 6, wherein

the row driver circuits and the column driver circuits are at a high impedance state during each sensing interval.

8. The display device of claim 1, wherein the display panel is an active matrix liquid crystal display panel having a transparent counter electrode disposed generally between the probe and the row and column electrodes

wherein openings are formed in the transparent counter electrode to allow capacitive coupling between the probe and the row and column electrodes.

9. The display device of claim 1, wherein

the display panel includes n rows of m color pixels, each color pixel comprising red, green, and blue sub-pixels

the row driver comprises n row driver circuits and n row sensing circuits

the column driver comprises 3m column driver circuits and m column sensing circuits.

10. A display device, comprising:

an active matrix liquid crystal display panel comprising

a transparent front plate having an outer surface and an inner surface

a back plate having an inner surface and an outer surface, the inner surface of the back plate facing the inner surface of the front plate

a liquid crystal material sandwiched between the inner surface of the front plate and the inner surface of the back plate

a transparent counter electrode disposed on the inner surface of the front plate

a plurality of column electrodes, a plurality of row electrodes, and a plurality of pixel electrodes disposed on the inner surface of the back plate

wherein openings are provided in the transparent counter electrode opposing selected pixel electrodes to allow capacitive coupling between the selected pixel electrodes and a probe proximate to the outer surface of the front plate.

11. The display device of claim 10, further comprising:

a column driver having respective column driver circuits for driving each of the plurality of column electrodes

a column sensor including column sensing circuits adapted to sense capacitive coupling between the selected pixel electrodes and a probe adjacent to the outer surface of the front plate.

12. The display device claim 10, wherein the selected pixel electrodes are the entire plurality of pixel electrodes.

13. The display device of claim 10, wherein

the probe is connect to an AC voltage source

the column sensing circuits sense the capacitive coupling to the probe by detecting a coupled AC voltage in the selected pixel electrodes.

14. The display device of claim 13, wherein

the AC voltage source has predetermined frequency

the column sensing circuits include filters selective for the predetermined frequency.