Directional backlight, 3D image display apparatus having the same, and method of manufacturing the same

1. A directional backlight comprising:

a light source;

a light guide plate comprising an entrance surface receiving light emitted from the light source, the light guide plate guiding the light emitted from the light source;

a diffractive device comprising a plurality of grating units configured to adjust a direction of light exiting the light guide plate; and

an aperture adjusting layer arranged on the diffractive device and comprising a plurality of apertures having different sizes.

2. The directional backlight of claim 1 , wherein each of the grating units comprises a plurality of sub-grating units, wherein the sub-grating units are dependent on different wavelength bands of light, and the apertures of the aperture adjusting layer respectively correspond to the sub-grating units.

3. The directional backlight of claim 2 , wherein the apertures of the aperture adjusting layer have different sizes so as to adjust aperture ratios of the corresponding sub-grating units.

4. The directional backlight of claim 1 , wherein the light source comprises a light source configured to emit light of a plurality of colors in different directions, the aperture adjusting layer comprises aperture units corresponding to the grating units, and each of the aperture units comprises a plurality of sub-apertures transmitting the light of the colors.

5. The directional backlight of claim 4 , wherein sizes of the sub-apertures increase in the directions in which the light of the colors propagates.

6. The directional backlight of claim 1 , wherein each of the grating units comprises a plurality of sub-grating units, wherein the sub-grating units are dependent on different wavelength bands of light, the aperture adjusting layer comprises aperture units corresponding to the grating units, and each of the aperture units comprises a plurality of sub-apertures respectively corresponding to the sub-grating units.

7. The directional backlight of claim 6 , wherein the sub-apertures have different size ratios in different aperture units.

8. The directional backlight of claim 6 , wherein the aperture adjusting layer is divided into a plurality of sections, and the sub-apertures of the aperture units have different size ratios in different sections.

9. A directional backlight comprising:

a light source emitting light of a plurality of colors;

a light guide plate comprising an entrance surface receiving the light emitted from the light source, the light guide plate guiding the light emitted from the light source; and

a diffractive device comprising a plurality of grating units configured to adjust a direction of the light of the colors when the light exits the light guide plate,

wherein each of the grating units comprises a plurality of sub-grating units corresponding to the light of the colors, and the sub-grating units have different refractive indexes such that output efficiency of the light of the colors increases in a direction away from the entrance surface of the light guide plate.

10. The directional backlight of claim 9 , wherein the diffractive device is divided into a plurality of sections, and refractive indexes of sub-grating units of grating units included in a section relatively distant from the entrance surface of the light guide plate are greater than refractive indexes of sub-grating units of grating units included in a section relatively close to the entrance surface of the light guide plate.

11. A three-dimensional (3D) image display apparatus comprising:

a directional backlight; and

a display panel forming images using light output from the directional backlight,

wherein the directional backlight comprises:

a light source;

a light guide plate comprising an entrance surface receiving light emitted from the light source, the light guide plate guiding the light emitted from the light source;

a diffractive device comprising a plurality of grating units configured to adjust a direction of light exiting the light guide plate; and

an aperture adjusting layer arranged on the diffractive device and comprising a plurality of apertures having different sizes.

12. A method of manufacturing a directional backlight, the method comprising:

forming grating units, each grating unit comprising a plurality of sub-grating units on a substrate, the sub-grating units comprising different diffraction patterns;

preparing a mask comprising an aperture array corresponding to the sub-grating units; and

etching the sub-grating units formed on the substrate using the mask such that the sub-grating units have different sizes.

13. The method of claim 12 , wherein the mask comprises mask aperture units corresponding to the grating units, and the mask aperture units comprise mask sub-apertures respectively corresponding to the sub-grating units.

14. The method of claim 12 , wherein the diffraction patterns have nano-sizes, and the aperture array has a micro-size.

15. The method of claim 12 , further comprising attaching a light guide plate to the substrate.

16. A method of manufacturing a directional backlight, the method comprising:

printing a first material pattern having a first refractive index on a substrate by an inkjet printing method;

printing a second material pattern having a second refractive index on the substrate by an inkjet printing method; and

forming diffraction patterns on the first and second material patterns by a nanoimprinting method.

17. The method of claim 16 , further comprising printing a third material pattern having a third refractive index on the substrate by an inkjet printing method.

18. The method of claim 16 , further comprising attaching a light guide plate to the substrate.

19. The method of claim 18 , wherein the first and second material patterns are configured to adjust output efficiency of light guided via the light guide plate.

20. The method of claim 19 , wherein the first and second material patterns are configured such that output efficiency of light guided via the light guide plate increases in a direction away from an entrance surface of the light guide plate.

21. The method of claim 16 , wherein the first and second material patterns comprise a plurality of grating units, and each of the grating units comprises a plurality of sub-grating units selectively diffracting light of different colors.

22. A directional backlight comprising:

a first light source emitting light in a first direction;

a second light source emitting light in a second direction;

a light guide plate comprising a first entrance surface receiving light emitted from the first light source and a second entrance surface receiving light emitted from the second light source; and

a diffractive device provided on a surface of the light guide plate that is orthogonal to the first entrance surface and the second entrance surface, the diffractive device comprising a plurality of grating units configured to adjust a direction of light exiting the light guide plate,

wherein the grating units are configured such that a grating unit relatively far away from the first entrance surface emits more light from the first light source than a grating unit relatively closer to the first entrance surface, and such that a grating unit relatively far away from the second entrance surface emits more light from the second light source than a grating unit relatively closer to the second entrance surface.

23. The directional backlight of claim 22 , wherein each grating unit comprises a plurality of sub-grating units, one sub-grating unit of the sub-grating units for light from the first light source, and another sub-grating unit of the sub-grating units for light from the second light source.

24. The directional backlight of claim 22 , further comprising an aperture adjusting layer arranged on the diffractive device and comprising a plurality of apertures.

25. The directional backlight of claim 23 , further comprising an aperture adjusting layer arranged on the diffractive device and comprising a plurality of apertures, the apertures respectively corresponding to the sub-grating units.

26. The directional backlight of claim 25 , wherein sizes of a portion of the apertures gradually increase as a distance from the first entrance surface increases, and sizes of a portion of the apertures gradually increase as a distance from the second entrance surface increases.