Display device and method for driving display device

• US 8,928,644 B2
• Filed: 02/15/2011
• Issued: 01/06/2015
• Est. Priority Date: 02/19/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kurokawa, Yoshiyuki, Ikeda, Takayuki, Tamura, Hikaru
• Primary Examiner(s): PATEL, PREMAL R
• Application Number:
  US13/027,583
• Publication Number:
  US 20110205209A1
• Time in Patent Office: 1,421 Days
• Field of Search: 345/60, 345/175, 345/204, 345/207, 345/211, 345/212
• US Class Current: 345/211
• CPC Class Codes: G01J 1/18 using comparison with a reference electric value
• CPC Class Codes: G01J 1/42 using electric radiation detectors optical or mechanical part G01J1/04; by comparison with a reference light or electric value G01J1/10
• CPC Class Codes: G01J 1/4204 with determination of ambient light solar light G01J2001/4266
• CPC Class Codes: G06F 3/04164 Connections between sensors and controllers, e.g. routing lines between electrodes and connection pads
• CPC Class Codes: G06F 3/042 by opto-electronic means
• CPC Class Codes: H01L 27/14612 involving a transistor
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers

Abstract

A display device includes a pixel which includes a first photosensor portion having a first photodiode for detecting visible light, which is provided together with a display element portion; and a pixel which includes a second photosensor portion having a second photodiode for detecting infrared rays, which is provided together with another display element portion. The second photosensor portion detects infrared rays included in external light, and selects an imaging element and adjusts sensitivity in accordance with the amount of infrared rays detected by the second photosensor portion.

Claims

1. A display device comprising:

a display region comprising a first pixel and a second pixel, the first pixel comprising;

a first semiconductor of a first transistor;

a second semiconductor of a second transistor;

an insulating film over the first semiconductor and the second semiconductor;

a first photodiode comprising a third semiconductor over the insulating film, the first photodiode electrically connected to the first transistor; and

a first display element over the insulating film, the first display element electrically connected to the second transistor; and

the second pixel comprising;

a fourth semiconductor of a third transistor;

a fifth semiconductor of a fourth transistor;

the insulating film over the fourth semiconductor and the fifth semiconductor;

a second photodiode comprising a sixth semiconductor over the insulating film, the second photodiode electrically connected to the third transistor; and

a second display element over the insulating film, the second display element electrically connected to the fourth transistor,

wherein the first photodiode is configured to detect visible light,

wherein a sensitivity of the first photodiode is adjustable, and

wherein the second photodiode is configured to detect an infrared ray.

3. The display device according to claim 1 or claim 2, wherein the first photodiode is a PIN-type photodiode in which amorphous silicon is used for an i-type semiconductor layer.

4. The display device according to claim 1 or claim 2, wherein the second photodiode is a PIN-type photodiode in which crystalline silicon is used for an i-type semiconductor layer.

5. The display device according to claim 1 or claim 2, wherein the second photodiode is provided with a filter which transmits infrared rays and absorbs visible light.

6. The display device according to claim 1 or claim 2, wherein each of the first display element and the second display element is a liquid crystal element.

7. The display device according to claim 1 or claim 2, wherein each of the first display element and the second display element is a light-emitting element.

8. An electronic device comprising the display device according to claim 1 or claim 2.

9. The display device according to claim 1 or claim 2,

wherein the third semiconductor is a different material from the first semiconductor and the second semiconductor, and

wherein the sixth semiconductor is a different material from the fourth semiconductor and the fifth semiconductor.

10. The display device according to claim 1 or claim 2,

wherein each of the first semiconductor, the second semiconductor, the fourth semiconductor and the fifth semiconductor comprises an oxide semiconductor.

2. A display device comprising:

a display region comprising a first pixel and a second pixel; and

a driving circuit electrically connected to the display region,

wherein the first pixel comprises;

a first semiconductor of a first transistor;

a second semiconductor of a second transistor;

an insulating film over the first semiconductor and the second semiconductor;

a first photodiode comprising a third semiconductor over the insulating film, the first photodiode electrically connected to the first transistor; and

a first display element over the insulating film, the first display element electrically connected to the second transistor,

wherein the second pixel comprises;

a fourth semiconductor of a third transistor;

a fifth semiconductor of a fourth transistor;

the insulating film over the fourth semiconductor and the fifth semiconductor;

a second photodiode comprising a sixth semiconductor over the insulating film, the second photodiode electrically connected to the third transistor; and

a second display element over the insulating film, the second display element electrically connected to the fourth transistor,

wherein the first photodiode is configured to detect visible light,

wherein a sensitivity of the first photodiode is adjustable, and

wherein the second photodiode is configured to detect an infrared ray.

11. A method for driving a display device, the display device comprising:

a display element portion formed in a pixel of a display region;

a first photosensor portion formed in the pixel, which is provided together with the display element portion; and

a second photosensor portion formed in another pixel without the first photosensor portion, which is provided together with another display element portion,

the method for driving the display device comprising;

changing light reception sensitivity of the first photosensor portion by intensity of an infrared ray which is detected by the second photosensor portion when light is received;

converting intensity of light detected by the first photosensor portion to signals;

forming from the signals a histogram where a horizontal axis represents a gray scale;

counting gray scales of the histogram from the gray scales in a dark side;

setting a gray scale which reaches a count number set in advance to a threshold value;

performing binarization of an image at a boundary of the threshold value to obtain a bright portion and a dark portion; and

determining a position of an object to be detected in the display region using an address of a pixel of the dark portion.

12. A method for driving a display device, the display device comprising:

a display element portion formed in a pixel of a display region;

a first photosensor portion formed in the pixel, which is provided together with the display element portion; and

a second photosensor portion formed in another pixel without the first photosensor portion, which is provided together with another display element portion,

the method for driving the display device comprising;

external light entering the display region;

detecting an infrared ray included in the external light by the second photosensor portion;

selecting either the first photosensor portion or the second photosensor portion as a unit which is used for imaging in accordance with an amount of infrared rays detected by the second photosensor portion;

performing imaging using visible light when the first photosensor portion is used;

performing imaging using an infrared ray when the second photosensor portion is used;

converting intensity of light detected by the first photosensor portion or the second photosensor portion to signals;

forming from the signals a histogram where a horizontal axis represents a gray scale;

counting gray scales of the histogram from the gray scales in a dark side;

setting a gray scale which reaches a count number set in advance to a threshold value;

performing binarization of an image at a boundary of the threshold value to obtain a bright portion and a dark portion; and

determining a position of an object to be detected in the display region using an address of a pixel of the dark portion.