DISPLAY DEVICE WITH OPTICAL SENSORS

• US 20090289915A1
• Filed: 05/20/2009
• Published: 11/26/2009
• Est. Priority Date: 05/21/2008
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.), Seoul National University Industry Foundation (Seoul National University)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Lee, Jae-Hoon, You, Bong-Hyun, Han, Min-Koo, Park, Hyun-Sang, Lee, Byoung-Jun
• Granted Patent: US 8,717,308 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/042 by opto-electronic means
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters

Abstract

A display device with a touch screen includes: first sensing units, each first sensing unit comprising first optical sensors connected in series, each first sensing unit comprising a first terminal for receiving a first voltage, each first sensing unit extending in a first direction; second sensing units, each second sensing unit comprising second optical sensors connected in series, each second sensing unit comprising a first terminal for receiving a second voltage, each second sensing unit extending in a second direction transverse to the first direction; a reset unit for applying a reset voltage to a second terminal of each of the first and second sensing units; and a read-out unit for sensing a touch position based on voltage changes at the second terminals of the first and second sensing units.

Claims

1. A display device comprising:

a plurality of first sensing units, each first sensing unit comprising first optical sensors connected in series to each other, each first sensing unit comprising a first terminal which receives a first voltage, each first sensing unit extending in a first direction;

a plurality of second sensing units, each second sensing unit comprising second optical sensors connected in series to each other, each second sensing unit comprising a first terminal which receives a second voltage, each second sensing unit extending in a second direction transverse to the first direction;

a reset unit which is connected to a second terminal of each of the first and second sensing units and is which applies a reset voltage to the second terminal of each of the first and second sensing units; and

a read-out unit which senses a touch position based on voltage changes at the second terminals of the first and second sensing units.

2. The display device of claim 1, wherein the first and second optical sensors are amorphous silicon (a-Si) thin-film transistors (TFTs).

3. The display device of claim 1, wherein the first and second optical sensors are TFTs.

4. The display device of claim 3, wherein the first and second optical sensors operate in a turn-off region.

5. The display device of claim 3, wherein an optical leakage current of each said optical sensor depends on an amount of external light impinging on the optical sensor'"'"'s channel region, and said voltage changes depend on the optical leakage currents.

6. The display device of claim 1, wherein the reset unit is for applying the reset voltage in the form of a pulse voltage at the beginning of a frame, and the read-out unit is for sensing the touch position based on the voltage changes during the frame.

7. The display device of claim 1, wherein the first and second optical sensors are photodiodes or photo conductors.

8. The display device of claim 1, wherein the reset unit comprises a plurality of switching devices which, when turned on by a reset start signal, apply the reset voltage to the second terminals of the first and second sensing units.

9. The display device of claim 8, wherein the reset start signal is transmitted to a gate electrode of each of the switching devices, the reset voltage is applied to a drain electrode of each of the switching devices, and the second terminal of each of the first and second sensing units is connected to a source electrode of a respective one of the switching devices.

10. The display device of claim 1, wherein the reset unit comprises switching devices for supplying electric charge to each of the first and second sensing units, and each of the first and second sensing units is associated with a capacitor for accumulating the electric charge.

11. The display device of claim 10, wherein the switching devices are simultaneously turned on by the reset start signal.

12. The display device of claim 10, wherein the capacitor is parasitic capacitor of the respective first and second sensing units.

13. The display device of claim 1, wherein the read-out unit comprises:

a plurality of comparators connected to the second terminals of the respective first and second sensing units; and

a multiplexer connected to the comparators, for sequentially outputting output signals of the respective comparators.

14. The display device of claim 13, wherein the read-out unit further comprises an addressor for transmitting a plurality of timing signals to the multiplexer at the end of a frame.

15. A display device comprising:

a plurality of sensing units each of which comprises a plurality of optical sensors operating in a turn-off region, each said sensing unit having a capacitor which converts, into a voltage change, a change in an optical leakage current that flows through the sensing unit'"'"'s optical sensors;

a reset unit which applies a reset voltage to each of the sensing units; and

a read-out unit which senses a touch position based on the voltage change caused by touching at least one of the optical sensors.

16. The display device of claim 15, wherein the optical sensors are a-Si TFTs.

17. The display device of claim 15, wherein the reset voltage is for being applied in the form of a pulse voltage at the beginning of a frame, and the read-out unit is for sensing the touch position based on the voltage changes during the frame.

18. A method of driving a display device, the method comprising:

biasing a plurality of optical sensors included in each of a plurality of sensing units so that the optical sensors operate in a turn-off region;

applying a reset voltage to a terminal of each of the sensing units;

converting, into a voltage change at the terminal of each of the sensing units, a change in an optical leakage current flowing through at least one of the optical sensors; and

sensing a touch position based on the voltage changes at the terminals of the sensing units.

19. The method of claim 18, wherein the reset voltage is applied in the form of a pulse voltage at the beginning of a frame, and the touch position is sensed based on the voltage changes during the frame.

20. The method of claim 18, wherein the touch position is sensed as a region of intersection of two sensing units which have the smallest voltage changes from among the sensing units.