Flat panel display with capacitance sensing touch screen

• US 8,373,667 B2
• Filed: 11/05/2008
• Issued: 02/12/2013
• 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
• Primary Examiner(s): Lefkowitz, Sumati
• Assistant Examiner(s): Hicks, Charles V
• Application Number:
  US12/265,414
• Publication Number:
  US 20100110035A1
• Time in Patent Office: 1,560 Days
• Field of Search: 345/174, 345/173
• US Class Current: 345/173
• 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:

an active matrix 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 coupled to at least some of the plurality of column electrodes, each column sensing circuit adapted to sense capacitive coupling between the respective column electrode 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; and

a row sensor including row sensing circuits coupled to at least some of the plurality of row electrodes, each row sensing circuit adapted to sense capacitive coupling between the respective row electrode and the probe, wherein

the display panel has a transparent counter electrode disposed generally between the probe and the row and column electrodes, and

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

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, and

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 connected to an AC voltage source, and

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, and

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, and

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 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,

the row sensor comprises n row sensing circuits,

the column driver comprises 3 m column driver circuits, and

the column sensor comprises m column sensing circuits.

9. 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; and

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.

10. The display device of claim 9, further comprising:

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

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.

11. The display device of claim 9, wherein the selected pixel electrodes are the entire plurality of pixel electrodes.

12. The display device of claim 9, wherein

the probe is connected to an AC voltage source, and

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

13. The display device of claim 12, wherein

the AC voltage source has predetermined frequency, and

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