LIQUID CRYSTAL DEVICE

• US 20090033850A1
• Filed: 07/25/2008
• Published: 02/05/2009
• Est. Priority Date: 08/01/2007
• Status: Active Grant

• Current Assignee: Japan Display West Incorporated (Japan Display Incorporated)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: OTA, Hitoshi, ISHIGURO, Hideto, KANDA, Eiji
• Granted Patent: US 8,089,476 B2
• Time in Patent Office: Days
• US Class Current: 349/116
• CPC Class Codes: G02F 1/13312 Circuits comprising photodetectors for purposes other than feedback
• 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 3/042 by opto-electronic means
• CPC Class Codes: G09G 2300/0465 Improved aperture ratio, e.g. by size reduction of the pixel circuit, e.g. for improving the pixel density or the maximum displayable luminance or brightness
• 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

Abstract

A liquid crystal device includes a plurality of selection lines, a plurality of signal lines, a plurality of pixel portions, a plurality of photosensor portions, a plurality of first power lines, and a plurality of sense lines. The plurality of selection lines are provided in a line direction. The plurality of signal lines are provided in a column direction. The plurality of pixel portions are provided at positions corresponding to intersections of the selection lines and the signal lines. The plurality of photosensor portions are provided in correspondence with a portion of the plurality of pixel portions. The plurality of first power lines are provided in the line direction. The plurality of sense lines are provided in the column direction. Each of the plurality of pixel portions includes a first switching element and a liquid crystal. The first switching element loads a display signal supplied through a corresponding one of the signal lines as a selection signal supplied through a corresponding one of the selection lines is asserted. The liquid crystal exhibits a bright state corresponding to the display signal that is loaded by the first switching element. The portion of the plurality of pixel portions adjust the amounts of light that enter the plurality of photosensor portions. Each of the plurality of photosensor portions includes a photoelectric conversion element, a capacitive element, a second switching element, and a readout portion. The photoelectric conversion element generates an electric current of which the magnitude corresponds to the amount of light received. One end of the capacitive element is electrically connected to the photoelectric conversion element. The second switching element resets the one end of the capacitive element to a reset voltage that is supplied through a corresponding one of the first power lines. The readout portion outputs, to a corresponding one of the sense lines, an output signal of which the magnitude corresponds to a voltage of the one end of the capacitive element. The second switching element is controlled to any one of an on state or an off state on the basis of the selection signal that is supplied through the corresponding one of the selection lines.

Claims

1. A liquid crystal device comprising:

a selection line that is provided in a line direction;

a first signal line and a second signal line that are provided in a column direction;

a first pixel portion and a second pixel portion that are provided at positions corresponding to intersections of the selection line and the signal lines;

a photosensor portion that is provided in correspondence with the second pixel portion;

a first power line that is provided in the line direction; and

a sense line that is provided in the column direction, wherein

each of the pixel portions includes a first switching element and a liquid crystal, wherein

the first switching element loads a display signal supplied through a corresponding one of the signal lines as a selection signal supplied through the selection line is asserted, wherein

the liquid crystal exhibits a bright state corresponding to the display signal that is loaded by the first switching element, wherein

the second pixel portion adjust the amounts of light that enter the photosensor portion, wherein

the photosensor portion includes a photoelectric conversion element, a capacitive element, a second switching element, and a readout portion, wherein

the photoelectric conversion element generates an electric current of which the magnitude corresponds to the amount of light received, wherein one end of the capacitive element is electrically connected to the photoelectric conversion element, wherein

the second switching element resets the one end of the capacitive element to a reset voltage that is supplied through the first power line, wherein

the readout portion outputs, to the sense line, an output signal of which the magnitude corresponds to a voltage of the one end of the capacitive element, and wherein

the second switching element is controlled to any one of an on state or an off state on the basis of the selection signal that is supplied through the selection line.

2. The liquid crystal device according to claim 1, further comprising:

a photosensor selection line that is provided in the line direction, wherein the readout portion includes a transistor and a third switching element, the transistor generates an output signal of which the magnitude corresponds to a voltage of the one end of the capacitive element, and the third switching element is provided between the transistor and the sense line and turns on as a photosensor selection signal supplied to the photosensor selection lines is asserted; and

a control portion that controls the photosensor portion so that, after the selection signal has been asserted, the photosensor selection signal is asserted to read out a reference light receiving signal onto the sense line as the output signal and, after a predetermined time has elapsed since the selection signal has been negated, the photosensor selection signal is asserted to read out a measurement light receiving signal onto the sense line as the output signal.

3. The liquid crystal device according to claim 1, further comprising:

a photosensor selection line that is provided in the line direction, wherein each readout portion includes a transistor and a third switching element, the transistor generates an output signal of which the magnitude corresponds to a voltage of the one end of the capacitive element, and the third switching element is provided between the transistor and the sense line and enters an on state as a photosensor selection signal supplied to the photosensor selection line is asserted; and

a control portion that controls the photosensor portion so that, after a predetermined time has elapsed since the selection signal had been switched from assertion to negation, the photosensor selection signal is asserted to read out a measurement light receiving signal onto the sense line as the output signal and, after the selection signal has been asserted, a reference light receiving signal is read out onto the sense line as the output signal.

7. The liquid crystal device according to claim 2, wherein the control portion outputs a difference between the reference light receiving signal and the measurement light receiving signal as a detected light receiving signal.

8. The liquid crystal device according to claim 1, wherein

each of the pixel portions includes a holding capacitive element that holds the display signal, wherein

one end of the holding capacitive element is electrically connected to the first switching element, and wherein

the other end of the holding capacitive element is electrically connected to the first power lines.

9. The liquid crystal device according to claim 1, further comprising:

a second power line that is provided in the line direction, wherein

the other end of the photoelectric conversion element is electrically connected to the second power line, wherein

each of the pixel portions includes a holding capacitive element that holds the display signal, wherein

one end of the holding capacitive element is electrically connected to the first switching element, and wherein

the other end of the holding capacitive element is electrically connected to the second power line.

4. A liquid crystal device comprising:

a selection line that is provided in a line direction;

a first signal line and a second signal line that are provided in a column direction;

a first pixel portion and a second pixel portion that are provided at position corresponding to intersections of the selection line and the signal lines;

a photosensor portion that is provided in correspondence with the second pixel portion;

a first power line that is provided in the line direction; and

a sense line that is provided in the column direction, wherein

each of the pixel portions includes a first switching element and a liquid crystal, wherein

the first switching element loads a display signal supplied through a corresponding one of the signal lines as a selection signal supplied through the selection line is asserted, wherein

the liquid crystal exhibits a bright state corresponding to the display signal that is loaded by the first switching element, wherein

the second pixel portion adjust the amounts of light that enter the photosensor portion, wherein

the photosensor portion includes a photoelectric conversion element, a capacitive element, a second switching element, a transistor, and a third switching element, wherein

the photoelectric conversion element generates an electric current of which the magnitude corresponds to the amount of light received, wherein one end of the capacitive element is electrically connected to the photoelectric conversion element, wherein

the second switching element resets the one end of the capacitive element to a reset voltage that is supplied through the first power line, wherein

the transistor generates an output signal of which the magnitude corresponds to a voltage of the one end of the capacitive element, wherein

the third switching element is provided between the transistor and the sense line, and wherein

the third switching element is controlled to any one of an on state or an off state on the basis of the selection signal that is supplied through the selection line.

5. The liquid crystal device according to claim 4, further comprising:

a reset signal line that is provided in the line direction; and

a control portion that controls the photosensor portion so that, after the selection signal and a reset signal that is supplied through the reset signal line have been asserted, a reference light receiving signal is read out onto the sense line as the output signal and, after a predetermined time has elapsed since the reset signal had been negated, the selection signal is asserted to read out a measurement light receiving signal onto the sense line as the output signal.

6. The liquid crystal device according to claim 4, further comprising:

a reset signal line that is provided in the line direction; and

a control portion that controls the photosensor portion so that, after a predetermined time has elapsed since a reset signal that is supplied through the reset signal line had been switched from assertion to negation, the photosensor selection signal is asserted to read out a measurement light receiving signal onto the sense line as the output signal and, after the selection signal has been asserted, a reference light receiving signal is read out onto the sense line as the output signal.

10. A liquid crystal device comprising:

selection lines that are provided in a line direction;

signal lines that are provided in a column direction;

first pixel portions that are provided at positions corresponding to intersections of the selection lines and the signal lines;

second pixel portions that are provided at positions corresponding to intersections of the selection lines located at every K lines (K is natural number) and the signal lines;

photosensor portions that are provided in correspondence with a portion of the second pixel portions;

first power lines that are provided in the line direction; and

sense lines that are provided in the column direction, wherein

each of the first pixel portions and second pixel portions includes a first switching element and a liquid crystal, wherein

the first switching element loads a display signal supplied through a corresponding one of the signal lines as a selection signal supplied through a corresponding one of the selection lines is asserted, wherein

the liquid crystal exhibits a bright state corresponding to the display signal that is loaded by the first switching element, wherein

the portion of the second pixel portions adjust the amounts of light that enter the photosensor portions, wherein

each of the photosensor portions includes a photoelectric conversion element, a second switching element, and a readout portion, wherein

the photoelectric conversion element generates an electric current of which the magnitude corresponds to the amount of light received, wherein

the second switching element resets one terminal of the photoelectric conversion element to a reset voltage that is supplied through a corresponding one of the first power lines, wherein

the readout portion outputs, to a corresponding one of the sense lines, an output signal of which the magnitude corresponds to a voltage of the one terminal of the photoelectric conversion element, and wherein

the switching element is controlled to any one of an on state or an off state on the basis of the selection signal that is supplied through a corresponding one of the selection lines located at every K lines.

11. The liquid crystal device according to claim 10, wherein K is 1, and wherein each second switching element is controlled to any one of an on state or an off state on the basis of the selection signal that is supplied through any one of successive two selection lines.

12. The liquid crystal device according to claim 11, wherein

the readout portion includes an amplification transistor and a switching device, wherein

the amplification transistor generates an output electric current of which the magnitude corresponds to a voltage of the one terminal of the photoelectric conversion element, and wherein

the switching device is provided between the amplification transistor and a corresponding one of the sense lines, and turns on as a photosensor selection signal that is supplied to a corresponding one of the selection lines is asserted, the liquid crystal device further comprising:

a control portion that controls each photosensor portion so that, as a selection signal supplied through the selection line of the one of any successive two lines has been asserted, a reference light receiving signal is read out onto the corresponding one of the sense lines as the output current and, after a predetermined time has elapsed since the selection signal supplied through the selection line of the one of any successive two lines had been negated, a measurement light receiving signal is read out onto the corresponding one of the sense line as the output current.

13. The liquid crystal device according to claim 12, wherein

the switching device includes a third switching element and a fourth switching element, wherein

the third switching element is provided between the amplification transistor and a corresponding one of the sense lines and is controlled to any one of an on state or an off state by the selection signal that is supplied through the selection line of one of any successive two lines, and wherein

the fourth switching element is provided between the amplification transistor and the corresponding one of the sense lines and is controlled to any one of an on state or an off state by a selection signal that is supplied through the selection line of the other one of any successive two lines.

14. The liquid crystal device according to claim 13, wherein

the selection line of the one of any successive two lines is the selection line such that a selection signal supplied therethrough is asserted first between the successive two selection lines, and wherein

the control portion controls the fourth switching element so that a selection signal supplied through the selection line of the other one of any successive two lines between the successive two selection lines is asserted second to read out a measurement light receiving signal onto a corresponding one of the sense lines as the output current.

15. The liquid crystal device according to claim 13, wherein

the selection line of one of any successive two lines is the selection line such that a selection signal supplied therethrough is asserted second between the successive two selection lines, and wherein

the control portion controls the third switching element so that a selection signal that is supplied through the selection line of the other one of any successive two lines is asserted after substantially one frame period has elapsed since a selection signal that is supplied to the selection line of the one of any successive two lines had been asserted to read out a measurement light receiving signal onto a corresponding one of the sense lines as the output current.

16. The liquid crystal device according to claim 10, further comprising:

a backflow prevention diode that is connected in series with the photoelectric conversion element.

17. The liquid crystal device according to claim 12, wherein the control portion outputs a difference between the reference light receiving signal and the measurement light receiving signal as a detected light receiving signal.

18. The liquid crystal device according to claim 10, wherein

each of the first pixel portions includes a holding capacitive element that holds the display signal, wherein one end of the holding capacitive element is electrically connected to the first switching element, and wherein

the other end of the holding capacitive element that is included in each first pixel portion of each one of successive two lines is connected to a corresponding one of the first power lines.

19. The liquid crystal device according to claim 18, further comprising:

second power lines, each of which is provided for the other one of the successive two lines, wherein

the other terminal of each photoelectric conversion element is electrically connected to the second power line of the other one of the successive two lines, and wherein

the electric potential supplied through each second power line is lower than the electric potential of a reset voltage supplied through each first power line.

20. The liquid crystal device according to claim 10, further comprising:

a capacitive element that is connected to the one terminal of the photoelectric conversion element.