Input-Output Device and Method for Driving the Same

• US 20110310062A1
• Filed: 06/15/2011
• Published: 12/22/2011
• Est. Priority Date: 06/16/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Ikeda, Takayuki, Kurokawa, Yoshiyuki
• Granted Patent: US 9,459,719 B2
• Time in Patent Office: Days
• US Class Current: 345/175
• 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 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

To increase the light detection accuracy, a method for driving an input-output device that includes a first light unit, a second light unit, a display circuit, and Y light detection circuits (Y is a natural number of 2 or more) is proposed. The same light-detection control signal is input to the Y light detection circuits. In a frame period set by a display selection signal, the first light unit is lit by sequentially switching Z light-emitting diodes and emitting light, and the second light unit is lit by making the white light-emitting diode emit light when the first light unit is not lit. In a period when the second light unit is lit, Y pieces of data corresponding to the illuminance of light entering the Y light detection circuits are generated.

Claims

1. An input-output device comprising:

a first light unit including Z light-emitting diodes, wherein Z is a natural number of 3 or more;

a second light unit including a white light-emitting diode and a light guide plate on which light from the white light-emitting diode is incident;

an X display circuit provided between the first light unit and the second light unit, configured to be supplied with a display selection signal and a display data signal in accordance with the display selection signal, and configured to be set in a display state corresponding to data of the display data signal, wherein X is a natural number; and

Y light detection circuits each provided between the first light unit and the second light unit, configured to be supplied with a light-detection control signal, and configured to generate data corresponding to illuminance of incident light in accordance with the light-detection control signal, wherein Y is a natural number of 2 or more.

2. The input-output device according to claim 1,

wherein each of the Y light detection circuits includes:

a photoelectric conversion element including a first current terminal and a second current terminal, wherein a current flows between the first current terminal and the second current terminal in accordance with the illuminance of the incident light;

a light-detection control transistor that is a field-effect transistor including a source and a drain, one of which is electrically connected to the second current terminal of the photoelectric conversion element, and a gate configured to be supplied with the light-detection control signal, and including an oxide semiconductor layer in which a channel is formed and a carrier concentration is lower than 1×

10¹⁴/cm³; and

an amplification transistor that is a field-effect transistor including a gate electrically connected to the other of the source and the drain of the light-detection control transistor, and a source and a drain from one of which data corresponding to the illuminance of the incident light is configured to output as a data signal.

3. The input-output device according to claim 2, wherein the photoelectric conversion element is a photodiode.

4. The input-output device according to claim 1, further comprising:

a read circuit configured to read data corresponding to the illuminance of the incident light from the Y light detection circuits; and

a data processing circuit configured to generate data of difference between two pieces of data corresponding to the illuminance of the incident light read from the read circuit.

5. The input-output device according to claim 1, wherein the Z light-emitting diodes are light-emitting diodes that emit light with a wavelength in a visible light region.

6. The input-output device according to claim 1, wherein the light from the white light-emitting diode is led to total reflection in the light guide plate.

7. The input-output device according to claim 1, wherein the white light-emitting diode is configured to emit light when the first light unit is not lit.

8. An input-output device comprising:

a first light unit including Z light-emitting diodes, wherein Z is a natural number of 3 or more;

a second light unit including a white light-emitting diode and a light guide plate on which light from the white light-emitting diode is incident;

an X display circuit provided between the first light unit and the second light unit, wherein X is a natural number; and

Y light detection circuits each provided between the first light unit and the second light unit, wherein Y is a natural number of 2 or more.

9. The input-output device according to claim 8,

wherein each of the Y light detection circuits includes:

a photoelectric conversion element;

a light-detection control transistor that is a field-effect transistor including an oxide semiconductor layer in which a channel is formed and a carrier concentration is lower than 1×

10¹⁴/cm³; and

an amplification transistor.

10. The input-output device according to claim 9, wherein the photoelectric conversion element is a photodiode.

11. The input-output device according to claim 8, further comprising:

a read circuit configured to read data corresponding to illuminance of incident light from the Y light detection circuits; and

a data processing circuit configured to generate data of difference between two pieces of data corresponding to the illuminance of the incident light read from the read circuit.

12. The input-output device according to claim 8, wherein the Z light-emitting diodes are light-emitting diodes that emit light with a wavelength in a visible light region.

13. The input-output device according to claim 8, wherein the light from the white light-emitting diode is led to total reflection in the light guide plate.

14. The input-output device according to claim 8, wherein the white light-emitting diode is configured to emit light when the first light unit is not lit.

15. A method for driving an input-output device comprising a first light unit including Z light-emitting diodes, wherein Z is a natural number of 3 or more;

a second light unit including a white light-emitting diode and a light guide plate on which light from the white light-emitting diode is incident;

an X display circuit provided between the first light unit and the second light unit, configured to be supplied with a display selection signal and a display data signal in accordance with the display selection signal, and configured to be set in a display state corresponding to data of the display data signal, wherein X is a natural number; and

Y light detection circuits each provided between the first light unit and the second light unit, configured to be supplied with a light-detection control signal, and configured to generate data corresponding to illuminance of incident light in accordance with the light-detection control signal, wherein Y is a natural number of 2 or more, the method comprising steps of;

inputting the light-detection control signal to each of the Y light detection circuits;

in a frame period set by the display selection signal, making the first light unit lit by sequentially switching the Z light-emitting diodes and emitting light, and making the second light unit lit by making the white light-emitting diode emit light when the first light unit is not lit; and

generating Y pieces of data corresponding to the illuminance of the incident light in a period when the second light unit is lit.

16. The method for driving the input-output device according to claim 15,

wherein each of the Y light detection circuits includes:

a photoelectric conversion element;

a light-detection control transistor that is a field-effect transistor including an oxide semiconductor layer in which a channel is formed and a carrier concentration is lower than 1×

10¹⁴/cm³; and

an amplification transistor.

17. The method for driving the input-output device according to claim 16, wherein the photoelectric conversion element is a photodiode.

18. The method for driving the input-output device according to claim 15, further comprising steps of:

reading data corresponding to the illuminance of the incident light from the Y light detection circuits; and

generating data of difference between two pieces of data corresponding to the illuminance of the incident light.

19. The method for driving the input-output device according to claim 15, wherein the Z light-emitting diodes are light-emitting diodes that emit light with a wavelength in a visible light region.

20. The method for driving the input-output device according to claim 18, wherein the light from the white light-emitting diode is led to total reflection in the light guide plate.

21. A method for driving an input-output device comprising a first light unit including Z light-emitting diodes, wherein Z is a natural number of 3 or more;

a second light unit including a white light-emitting diode and a light guide plate on which light from the white light-emitting diode is incident;

an X display circuit provided between the first light unit and the second light unit, configured to be supplied with a display selection signal and a display data signal in accordance with the display selection signal, and configured to be set in a display state corresponding to data of the display data signal, wherein X is a natural number; and

Y light detection circuits each provided between the first light unit and the second light unit, configured to be supplied with a light-detection control signal, and configured to generate data corresponding to illuminance of incident light in accordance with the light-detection control signal, wherein Y is a natural number of 2 or more, the method comprising steps of;

inputting the light-detection control signal to each of the Y light detection circuits;

in a frame period set by the display selection signal, making the first light unit lit by sequentially switching the Z light-emitting diodes and emitting light, and making the second light unit lit by making the white light-emitting diode emit light when the first light unit is not lit;

generating Y pieces of first data corresponding to first illuminance of the incident light in a first period when the second light unit is lit;

generating Y pieces of second data corresponding to second illuminance of the incident light in a second period when the first light unit and the second light unit are not lit; and

generating third data that is data of difference between the first data and the second data.

22. The method for driving the input-output device according to claim 21,

wherein each of the Y light detection circuits includes:

a photoelectric conversion element;

a light-detection control transistor that is a field-effect transistor including an oxide semiconductor layer in which a channel is formed and a carrier concentration is lower than 1×

10¹⁴/cm³; and

an amplification transistor.

23. The method for driving the input-output device according to claim 22, wherein the photoelectric conversion element is a photodiode.

24. The method for driving the input-output device according to claim 21, further comprising steps of:

reading data corresponding to the illuminance of the incident light from the Y light detection circuits; and

generating data of difference between two pieces of data corresponding to the illuminance of the incident light.

25. The method for driving the input-output device according to claim 21, wherein the Z light-emitting diodes are light-emitting diodes that emit light with a wavelength in a visible light region.

26. The method for driving the input-output device according to claim 21, wherein the light from the white light-emitting diode is led to total reflection in the light guide plate.