Display device and semiconductor device

• US 8,988,405 B2
• Filed: 10/20/2010
• Issued: 03/24/2015
• Est. Priority Date: 10/26/2009
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Endo, Masami
• Primary Examiner(s): PHAM, VIET DAVID
• Application Number:
  US12/908,299
• Publication Number:
  US 20110096047A1
• Time in Patent Office: 1,616 Days
• Field of Search: 345/102, 345/204
• US Class Current: 345/207
• CPC Class Codes: G01J 1/04 Optical or mechanical part supplementary adjustable parts
• CPC Class Codes: G01J 1/32 adapted for automatic variation of the measured or reference value regulation of light intensity G05D25/00
• CPC Class Codes: G02F 1/13312 Circuits comprising photodetectors for purposes other than feedback
• CPC Class Codes: G02F 1/13318 Circuits comprising a photodetector
• CPC Class Codes: G02F 1/133626 providing two modes of illumination, e.g. day-night
• CPC Class Codes: G02F 1/136281 having a transmissive semiconductor substrate
• CPC Class Codes: G02F 1/136295 Materials; Compositions; Manufacture processes
• CPC Class Codes: G02F 1/13793 Blue phases
• CPC Class Codes: G02F 2201/58 Arrangements comprising a monitoring photodetector
• CPC Class Codes: G02F 2203/30 Gray scale
• CPC Class Codes: G02F 2203/68 Green display, e.g. recycling, reduction of harmful substances
• 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 2354/00 Aspects of interface with display user
• CPC Class Codes: G09G 2360/148 the light being detected by light detection means within each pixel
• CPC Class Codes: G09G 3/3225 using an active matrix
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: H04N 1/00129 with a display device, e.g. CRT or LCD monitor with a television apparatus H04N1/00283; arrangements for control of display devices G09G
• CPC Class Codes: H05B 45/12 using optical feedback
• CPC Class Codes: H05B 47/11 by determining the brightness or colour temperature of ambient light
• CPC Class Codes: H10K 59/13 : comprising photosensors that control luminance
• CPC Class Codes: H10K 59/60 : OLEDs integrated with inorganic light-sensitive elements, e.g. with inorganic solar cells or inorganic photodiodes
• CPC Class Codes: Y02B 20/40 : Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

An object is to detect reflected light from an object accurately and to improve accuracy of capturing an image in a photosensor included in a display panel. In the display panel including a photosensor, when an image of an object is captured, light is emitted from a light source to the object and reflected light enters the photosensor. In the case where the incident light is too strong with respect to sensitivity of the photosensor, luminance of the light source is lowered. In the case where the incident light is too weak with respect to sensitivity of the photosensor, the luminance of the light source is increased.

Claims

1. A semiconductor device comprising:

a photosensor;

a light source; and

a controller,

wherein the light source is configured to irradiate paper with light,

wherein the photosensor is configured to detect the light reflected by the paper, and

wherein the controller is configured to lower the luminance of the light from the light source when the luminance of the light detected by the photosensor is higher than a first value and to increase the luminance of the light from the light source when the luminance of the light detected by the photosensor is lower than a second value.

2. The semiconductor device according to claim 1, wherein the light source comprises an LED.

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

an A/D converter configured to convert data of the paper into a digital signal; and

a bit count measurement portion configured to count a bit count number of each bit of the digital signal.

4. The semiconductor device according to claim 1, further comprising a pixel electrode for displaying an image, wherein the light source is configured to irradiate the paper with the light through the pixel electrode.

5. The semiconductor device according to claim 4, further comprising a thin film transistor,

wherein the thin film transistor is electrically connected to the pixel electrode, and

wherein the photosensor and the thin film transistor overlap with each other.

31. The semiconductor device according to claim 1,

wherein a light-emitting element serves as the light source, and

wherein the semiconductor device has a function of displaying an image by applying voltage to the light-emitting element.

6. A semiconductor device comprising:

an input portion comprising a photosensor;

a light source;

an A/D converter;

a bit count measurement portion; and

a controller,

wherein the light source is configured to irradiate paper with light,

wherein the input portion is configured to capture data of the paper by receiving the light reflected from the paper by the photosensor,

wherein the A/D converter is configured to convert the data of the paper into a digital signal,

wherein the bit count measurement portion is configured to count a bit count number of each bit of the digital signal, and

wherein the controller is configured to lower the luminance of the light from the light source when the bit count number is higher than a first value and to increase the luminance of the light from the light source when the bit count number is lower than a second value.

7. The semiconductor device according to claim 6, wherein the light source comprises an LED.

8. The semiconductor device according to claim 6, wherein the data of the paper is image data.

9. The semiconductor device according to claim 6, further comprising a pixel electrode for displaying an image, wherein the light source is configured to irradiate the paper with the light through the pixel electrode.

10. The semiconductor device according to claim 9, further comprising a thin film transistor,

wherein the thin film transistor is electrically connected to the pixel electrode, and

wherein the photosensor and the thin film transistor overlap with each other.

11. The semiconductor device according to claim 6, wherein the controller is configured to adjust luminance of the light from the light source so that the bit count number of a central bit is the highest.

12. The semiconductor device according to claim 6, wherein the controller is configured to adjust luminance of the light from the light source so that an average of the bit count number comes to a medium value of a maximum value of the bit count number.

32. The semiconductor device according to claim 6,

wherein a light-emitting element serves as the light source, and

wherein the semiconductor device has a function of displaying an image by applying voltage to the light-emitting element.

13. A display device comprising:

a display panel comprising a display element and a photosensor;

a backlight;

an A/D converter;

a bit count measurement portion; and

a controller,

wherein the backlight is configured to irradiate paper with light,

wherein the display panel is configured to capture data of the paper by receiving the light reflected from the paper by the photosensor,

wherein the A/D converter is configured to convert the data of the paper into a digital signal,

wherein the bit count measurement portion is configured to count a bit count number of each bit of the digital signal, and

wherein the controller is configured to lower the luminance of the light from the backlight when the bit count number is higher than a first value and to increase the luminance of the light from the backlight when the bit count number is lower than a second value.

14. The display device according to claim 13, wherein the backlight comprises an LED.

15. The display device according to claim 13, wherein the data of the paper is image data.

16. The display device according to claim 13, further comprising a pixel electrode for displaying an image, wherein the backlight is configured to irradiate the paper with the light through the pixel electrode.

17. The display device according to claim 16, further comprising a thin film transistor,

wherein the thin film transistor is electrically connected to the pixel electrode, and

wherein the photosensor and the thin film transistor overlap with each other.

18. The display device according to claim 13, wherein the controller is configured to adjust luminance of the light from the backlight so that the bit count number of a central bit is the highest.

19. The display device according to claim 13, wherein the controller is configured to adjust luminance of the light from the backlight so that an average of the bit count number comes to a medium value of a maximum value of the bit count number.

20. The display device according to claim 13, wherein the display element is a liquid crystal element or an EL element.

21. A semiconductor device comprising:

a photosensor;

a light source; and

a controller,

wherein the light source is configured to irradiate a human finger with light,

wherein the photosensor is configured to detect the light reflected by the human finger, and

wherein the controller is configured to lower the luminance of the light from the light source when the luminance of the light detected by the photosensor is higher than a first value and to increase the luminance of the light from the light source when the luminance of the light detected by the photosensor is lower than a second value.

22. The semiconductor device according to claim 21, wherein the light source comprises an LED.

23. The semiconductor device according to claim 21, further comprising:

an A/D converter configured to convert data of the human finger into a digital signal; and

a bit count measurement portion configured to count a bit count number of each bit of the digital signal.

24. The semiconductor device according to claim 21, further comprising a pixel electrode for displaying an image, wherein the light source is configured to irradiate the human finger with the light through the pixel electrode.

25. The semiconductor device according to claim 24, further comprising a thin film transistor,

wherein the thin film transistor is electrically connected to the pixel electrode, and

wherein the photosensor and the thin film transistor overlap with each other.

33. The semiconductor device according to claim 21,

wherein a light-emitting element serves as the light source, and

wherein the semiconductor device has a function of displaying an image by applying voltage to the light-emitting element.

26. A semiconductor device comprising:

a light source;

a first substrate over the light source;

a photosensor over the first substrate;

a second substrate over the photosensor; and

a controller,

wherein the semiconductor device is configured such that light from the light source enters through the first substrate and exits from the second substrate,

wherein the semiconductor device is configured such that light from the second substrate enters the photosensor and is detected by the photosensor, and

wherein the controller is configured to lower the luminance of the light from the light source when the luminance of the light detected by the photosensor is higher than a first value and to increase the luminance of the light from the light source when the luminance of the light detected by the photosensor is lower than a second value.

27. The semiconductor device according to claim 26, wherein the light source comprises an LED.

28. The semiconductor device according to claim 26, further comprising:

an A/D converter configured to convert data of the light detected by the photosensor into a digital signal; and

a bit count measurement portion configured to count a bit count number of each bit of the digital signal.

29. The semiconductor device according to claim 26, further comprising a pixel electrode for displaying an image, wherein the light from the light source exits from the second substrate through the pixel electrode.

30. The semiconductor device according to claim 29, further comprising a thin film transistor,

wherein the thin film transistor is electrically connected to the pixel electrode, and

wherein the photosensor and the thin film transistor overlap with each other.

34. The semiconductor device according to claim 26,

wherein a light-emitting element serves as the light source, and

wherein the semiconductor device has a function of displaying an image by applying voltage to the light-emitting element.