DISPLAY DEVICE

• US 20110109601A1
• Filed: 07/01/2009
• Published: 05/12/2011
• Est. Priority Date: 07/16/2008
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Brown, Christopher, Katoh, Hiromi
• Granted Patent: US 8,427,464 B2
• Time in Patent Office: Days
• US Class Current: 345/204
• 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 2360/148 the light being detected by light detection means within each pixel
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: H01L 31/035272 characterised by at least one potential jump barrier or surface barrier
• CPC Class Codes: H01L 31/153 formed in, or on, a common substrate

Abstract

Provided is a display device including a photoreception unit on an active matrix substrate in correspondence with one or two or more pixels, and a driving unit that drives the photoreception unit. The photoreception unit includes a photodiode, a capacitor that accumulates a charge in accordance with the electrical signal from when a reset signal (RST) from the driving unit has switched from the high level to the low level to when a readout signal (RWS) at the high level from the driving unit has been applied, and a switching element that, while the readout signal (RWS) is at the high level, allows output of a photoreception signal whose output level changes in accordance with the amount of accumulated charge. In a row selection period, after writing of an image signal to pixel electrodes in the row selected in the row selection period has ended, the driving unit switches the reset signal (RST) applied to the photoreception unit in the same row from the high level to the low level.

Claims

1. A display device comprising an active matrix substrate on which pixels having an active element and a pixel electrode are disposed in a matrix, the display device comprising:

a photoreception unit provided on the active matrix substrate in correspondence with one or two or more of the pixels, and a driving unit that drives the photoreception unit,

wherein the photoreception unit comprises a photodiode that outputs an electrical signal in accordance with an amount of received light, a capacitor that accumulates a charge in accordance with the electrical signal from when a reset signal from the driving unit has switched from a high level to a low level to when a readout signal at a high level has been applied from the driving unit, and a switching element that, while the readout signal is at the high level, allows output of a photoreception signal whose output level changes in accordance with the amount of accumulated charge, and

in a row selection period, after writing of an image signal to the pixel electrodes in the row selected in the row selection period has ended, the driving unit switches the reset signal applied to the photoreception unit in the same row from the high level to the low level.

2. The display device according to claim 1, wherein in a row selection period, after writing of an image signal to the pixel electrodes in the row selected in the row selection period has ended, the driving unit switches the reset signal applied to the row from the low level to the high level, and after a subsequent predetermined time period has elapsed, switches the reset signal applied to the row from the high level to the low level, and in the next row selection period, the driving unit switches the readout signal applied to the row from the low level to the high level.

3. The display device according to claim 1, wherein in a row selection period, before writing of an image signal to the pixel electrodes in the row selected in the row selection period starts, the driving unit switches the reset signal applied to the row from the low level to the high level, and after the writing of the image signal has ended, switches the reset signal applied to the row from the high level to the low level, and in the next row selection period, the driving unit switches the readout signal applied to the row from the low level to the high level.

4. The display device according to claim 3, wherein in a row selection period, before writing that accompanies a change in an image signal to the pixel electrodes in the row selected in the row selection period starts, the driving unit switches the reset signal applied to the row from the low level to the high level, and after the writing that accompanies a change in the image signal has ended, switches the reset signal applied to the row from the high level to the low level, and in the next row selection period, the driving unit switches the readout signal applied to the row from the low level to the high level.

5. The display device according to claim 2,

wherein the switching element is configured by one transistor,

wiring that supplies the reset signal is connected to an anode of the photodiode,

a control electrode of the transistor and a cathode of the photodiode are connected to one electrode of the capacitor,

one of two electrodes other than the control electrode of the transistor is connected to wiring that supplies a constant voltage, and the other of the two electrodes is connected to wiring that outputs the photoreception signal, and

wiring that supplies the readout signal is connected to another electrode of the capacitor.

6. The display device according to claim 2,

wherein the switching element is configured by a first transistor and a second transistor,

wiring that supplies the reset signal is connected to an anode of the photodiode,

a control electrode of the first transistor and a cathode of the photodiode are connected to one electrode of the capacitor,

one of two electrodes other than the control electrode of the first transistor is connected to wiring that supplies a constant voltage,

the other of the two electrodes other than the control electrode of the first transistor is connected to one of two electrodes other than a control electrode of the second transistor,

the readout signal wiring is connected to the control electrode of the second transistor,

the one of two electrodes other than the control electrode of the second transistor is connected to wiring that supplies the constant voltage, and

the other of the two electrodes other than the control electrode of the second transistor is connected to the readout wiring for output current.

7. The display device according to claim 1,

wherein the switching element is configured by a first transistor, a second transistor, and a third transistor,

wiring that supplies the reset signal is connected to a control electrode of the third transistor,

a control electrode of the first transistor, a cathode of the photodiode, and one of two electrodes other than the control electrode of the third transistor are connected to one electrode of the capacitor,

one of two electrodes other than the control electrode of the first transistor is connected to wiring that supplies a constant voltage,

the other of the two electrodes other than the control electrode of the first transistor is connected to one of two electrodes other than a control electrode of the second transistor,

the readout signal wiring is connected to the control electrode of the second transistor,

the one of two electrodes other than the control electrode of the second transistor is connected to wiring that supplies the constant voltage,

the other of the two electrodes other than the control electrode of the second transistor is connected to the readout wiring for output current,

the other of the two electrodes other than the control electrode of the third transistor is connected to wiring that supplies the constant voltage, and

an anode of the photodiode and another electrode of the capacitor are connected to ground wiring.

8. The display device according to claim 1, further comprising:

a common substrate opposing the active matrix substrate; and

liquid crystal sandwiched between the active matrix substrate and the common substrate.