BACKLIGHT UNIT PROVIDING UNIFORM LIGHT AND DISPLAY APPARATUS INCLUDING THE SAME

• US 20190317264A1
• Filed: 04/03/2019
• Published: 10/17/2019
• Est. Priority Date: 04/16/2018
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: DUBININ, German B., Dubynin, Sergey E., Morozov, Aleksander V., Putilin, Andrey N., Kopenkin, Sergey S., Borodin, Yuriy P., An, Jungkwuen, Choi, Chilsung, Lee, Hongseok, Song, Hoon, Kim, Sunil
• Granted Patent: US 10,761,256 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 5/0252 using holographic or diffractive means
• CPC Class Codes: G02B 5/18 Diffraction gratings holographic optical elements G02B5/32, G03H; integrally combined with optical fibres G02B6/02057; for coupling light guides G02B6/34; integrally combined with optical integrated light guides G02B6/12; grating systems G02B27/44
• CPC Class Codes: G02B 6/0026 Wavelength selective element, sheet or layer, e.g. filter or grating
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0076 Stacked arrangements of multiple light guides of the same or different cross-sectional area
• CPC Class Codes: G02B 6/0091 of the light source relative to the light guide G02B6/0021 takes precedence
• CPC Class Codes: G02F 1/133602 Direct backlight
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G09G 2300/023 Display panel composed of stacked panels
• CPC Class Codes: G09G 3/22 using controlled light sources

Abstract

Provided is a backlight unit including a light source emitting coherent light, a light guide plate propagating the light emitted by the light source, an input grating inputting the light from the light source into the light guide plate, an output grating provided on one surface of the light guide plate and diffracting light incident from inside the light guide plate and outputting the light, in a direction toward the outside of the light guide plate, a first recuperation element provided on one surface of the light guide plate and including a first recycle grating, and a second recuperation element provided opposite to the first recuperation element and directing, to the first recuperation element, incident light that is propagating inside the light guide plate.

Claims

1. A backlight unit comprising:

a light source configured to emit light;

a light guide plate comprising a first surface, a second surface that is opposite to the first surface in a first direction, a third surface, and a fourth surface that is opposite to the third surface in a second direction, the second direction being different from the first direction;

an input grating provided on the light guide plate adjacent to the third surface, the input grating being configured to input the light emitted by the light source into the light guide plate such that the light input is totally reflected inside of the light guide plate;

an output grating provided on one of the first surface and the second surface of the light guide plate, the output grating being configured to diffract light that is incident on the output grating from inside of the light guide plate and output the light toward an outside of the light guide plate;

a first recuperation element provided on the one of the first surface and the second surface of the light guide plate and adjacent to the fourth surface, the first recuperation element comprising a first recycle grating; and

a second recuperation element provided on the other one of the first surface and the second surface of the light guide plate opposite to the first recuperation element in the first direction, the second recuperation element being configured to direct, to the first recuperation element, the light propagating inside the light guide plate that is incident on the second recuperation element.

2. The backlight unit of claim 1, wherein the light propagating inside the light guide plate comprises direct propagating light that does not propagate through the first recuperation element and the second recuperation element, and recuperation propagating light that propagates through at least one of the first recuperation element and the second recuperation element, and

wherein the first recuperation element and the second recuperation element are configured such that the recuperation propagating light has a certain path difference from the direct propagating light.

3. The backlight unit of claim 2, wherein the first recuperation element is configured to diffract the recuperation propagating light toward the inside of the light guide plate, and

wherein the first recycle grating is configured to maximize negative second-order diffracted light directed toward the inside of the light guide plate.

4. The backlight unit of claim 2, wherein the output grating comprises a diffraction pattern that is configured to output the direct propagating light and the recuperation propagating light in parallel to each other.

5. The backlight unit of claim 4, wherein the diffraction pattern is set such that an intensity distribution trend of the direct propagating light output through the output grating and an intensity distribution trend of the recuperation propagating light output through the output grating are opposite to each other in a direction from the input grating to the first recuperation element.

6. The backlight unit of claim 1, wherein the second recuperation element comprises a mirror.

7. The backlight unit of claim 1, wherein the second recuperation element comprises a second recycle grating.

8. The backlight unit of claim 7, wherein the output grating, the first recycle grating, and the second recycle grating are mirror-coated.

9. The backlight unit of claim 1, further comprising a dichroic layer provided on the first surface or the second surface of the light guide plate, the dichroic layer being configured to reflect light of a certain wavelength band,

wherein the dichroic layer is further configured to reflect, back toward the output grating, light that is not output to the outside of the light guide plate from among the light incident on the output grating.

10. The backlight unit of claim 9, wherein the dichroic layer is further configured to reflect light incident on the dichroic layer at a certain angle.

11. The backlight unit of claim 9, wherein the dichroic layer is further configured to reflect negative first-order diffracted light that is diffracted by the output grating.

12. The backlight unit of claim 9, wherein one of the output grating and the dichroic layer is provided on the first surface of the light guide plate and the other of the output grating and the dichroic layer is provided on the second surface of the light guide plate.

13. The backlight unit of claim 9, wherein the output grating comprises a relief pattern, and

wherein the dichroic layer is provided on the relief pattern.

14. The backlight unit of claim 13, further comprising an immersion layer covering the relief pattern,

wherein the dichroic layer is provided on the immersion layer opposite to the relief pattern.

15. The backlight unit of claim 1, further comprising a mirror layer provided on the first surface or the second surface of the light guide plate, the mirror layer being configured to reflect, back toward the output grating, light that is not output to the outside of the light guide plate from among the light incident on the output grating.

31. The backlight unit of claim 9, wherein the output grating comprises a relief pattern,

wherein the backlight unit further comprises an immersion layer covering the relief pattern, and

wherein the dichroic layer is provided between the immersion layer and the light guide plate.

32. The backlight unit of claim 9, wherein the output grating comprises a relief pattern, and

wherein the dichroic layer is provided on the light guide plate opposite to the relief pattern in the first direction.

16. A display apparatus comprising:

a backlight unit comprising;

a light source configured to emit light;

a light guide plate comprising a first surface, a second surface that is opposite to the first surface in a first direction, a third surface, and a fourth surface that is opposite to the third surface in a second direction, the second direction being different from the first direction;

an input grating provided on the light guide plate adjacent to the third surface, the input grating being configured to input the light emitted by the light source into the light guide plate such that the light input is totally reflected inside of the light guide plate;

an output grating provided on one of the first surface and the second surface of the light guide plate, the output grating being configured to diffract light that is incident on the output grating from inside of the light guide plate and output the light toward an outside of the light guide plate;

a first recuperation element provided on the one of the first surface and the second surface of the light guide plate and adjacent to the fourth surface, the first recuperation element comprising a first recycle grating; and

a second recuperation element provided on the other one of the first surface and the second surface of the light guide plate opposite to the first recuperation element in the first direction, the second recuperation element being configured to direct, to the first recuperation element, the light propagating inside the light guide plate that is incident on the second recuperation element; and

a spatial light modulator configured to form a hologram image based on the light from the backlight unit.

17. A backlight unit comprising:

a light source configured to emit light of a certain wavelength band;

a light guide plate comprising a first surface, a second surface that is opposite to the first surface in a first direction, a third surface, and a fourth surface that is opposite to the third surface in a second direction, the second direction being different from the first direction;

an input grating provided on the light guide plate adjacent to the third surface, the input grating being configured to input the light emitted by the light source into the light guide plate such that the light input is totally reflected inside of the light guide plate;

an output grating provided on one of the first surface and the second surface of the light guide plate, the output grating being configured to diffract light that is incident on the output grating from inside of the light guide plate and output the light in a direction toward an outside of the light guide plate; and

a dichroic layer provided on the first surface or the second surface of the light guide plate, the dichroic layer being configured to reflect light of the certain wavelength band that is incident on the first surface or the second surface, at an angle smaller than a critical angle of total internal reflection of the light guide plate, toward the output grating.

18. The backlight unit of claim 17, further comprising:

a first recuperation element provided on one of the first surface and the second surface and adjacent to the fourth surface, the first recuperation element comprising a first recycle grating; and

a second recuperation element provided opposite to the first recuperation element in the first direction, the second recuperation element being configured to direct, to the first recuperation element, light propagating inside the light guide plate that is incident on the second recuperation element.

19. The backlight unit of claim 18, wherein the light propagating inside the light guide plate comprises direct propagating light that does not propagate through the first recuperation element and the second recuperation element, and recuperation propagating light that propagates through at least one of the first recuperation element and the second recuperation element, and

wherein the first recuperation element and the second recuperation element are configured such that the recuperation propagating light has a certain path difference from the direct propagating light.

20. The backlight unit of claim 19, wherein the first recuperation element is configured to diffract the recuperation propagating light toward an inside of the light guide plate, and

wherein the first recycle grating is configured to maximize negative second-order diffracted light directed toward the inside of the light guide plate.

21. The backlight unit of claim 19, wherein the output grating comprises a diffraction pattern that is configured to output the direct propagating light and the recuperation propagating light in parallel to each other.

22. The backlight unit of claim 21, wherein the diffraction pattern is configured such that an intensity distribution trend of the direct propagating light output through the output grating and an intensity distribution trend of the recuperation propagating light output through the output grating are opposite to each other in a direction from the input grating to the first recuperation element.

23. The backlight unit of claim 18, wherein the second recuperation element comprises a mirror.

24. The backlight unit of claim 18, wherein the second recuperation element comprises a second recycle grating.

25. The backlight unit of claim 24, wherein the output grating, the first recycle grating, and the second recycle grating are mirror-coated.

26. The backlight unit of claim 17, wherein the dichroic layer is further configured to reflect negative first-order diffracted light that is diffracted by the output grating.

27. The backlight unit of claim 17, wherein one of the output grating and the dichroic layer is provided on the first surface of the light guide plate and the other one of the output grating and the dichroic layer is provided on the second surface of the light guide plate.

28. The backlight unit of claim 17, wherein the output grating comprises a relief pattern, and

wherein the dichroic layer is provided on the relief pattern.

29. The backlight unit of claim 28, further comprising an immersion layer covering the relief pattern, and

wherein the dichroic layer is provided on the immersion layer opposite to the relief pattern.

30. A display apparatus comprising:

a backlight unit comprising;

a light source configured to emit light of a certain wavelength band;

a light guide plate comprising a first surface, a second surface that is opposite to the first surface in a first direction, a third surface, and a fourth surface that is opposite to the third surface in a second direction, the second direction being different from the first direction;

an input grating provided on the light guide plate adjacent to the third surface, the input grating being configured to input the light emitted by the light source into the light guide plate such that the light input is totally reflected inside of the light guide plate;

an output grating provided on one of the first surface and the second surface of the light guide plate, the output grating being configured to diffract light that is incident on the output grating from inside of the light guide plate and output the light in a direction toward an outside of the light guide plate; and

a dichroic layer provided on the first surface or the second surface of the light guide plate, the dichroic layer being configured to reflect light of the certain wavelength band that is incident on the first surface or the second surface, at an angle smaller than a critical angle of total internal reflection of the light guide plate, toward the output grating; and

a spatial light modulator configured to form a hologram image based on the light from the backlight unit.