Illumination apparatus for display device using hologram-based light guide plate (LGP)

• US 20060126142A1
• Filed: 12/14/2005
• Published: 06/15/2006
• Est. Priority Date: 12/14/2004
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Choi, Jin-Seung
• Granted Patent: US 7,859,731 B2
• Time in Patent Office: Days
• US Class Current: 359/15
• CPC Class Codes: G02B 27/0944 Diffractive optical elements, e.g. gratings, holograms gratings per se G02B5/18; holograms used as optical elements per se G02B5/32
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G02B 6/0018 Redirecting means on the surface of the light guide
• CPC Class Codes: G02B 6/0033 Means for improving the coupling-out of light from the light guide
• CPC Class Codes: G02B 6/0043 provided on the surface of the light guide
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 2203/22 diffractive

Abstract

An illumination apparatus and method for a display device designed such that light is incident on a hologram or hologram pattern at an angle for which diffraction efficiency is the highest. The illumination apparatus includes at least one point light source which emits light and a light guide plate (LGP) which has the at least one point light source disposed on a side thereof and a hologram pattern on a top surface which permits the light incident from the point light source to exit from the top surface. The side of the LGP facing the point light source is inclined such that the light is incident obliquely on the hologram pattern at an altitude angle which provides high diffraction efficiency.

Claims

1. An illumination apparatus for a display device, comprising:

at least one point light source that emits light; and

a light guide plate (LGP) comprising a hologram pattern on a top surface thereof, wherein;

the side of the LGP facing the at least one point light source is configured such that the light emitted from the at least one point light source is incident obliquely on the hologram pattern; and

at least a portion of the incident light exits from the top surface of the LGP.

2. The apparatus of claim 1, wherein the light emitted from the at least one point light source is incident obliquely on the hologram pattern with an altitude angle which provides the highest diffraction efficiency.

3. The apparatus of claim 1, wherein the side of the LGP facing the at least one point light source is inclined.

4. The apparatus of claim 3, wherein the at least one point light source is disposed obliquely so as to be parallel to the inclined side of the LGP.

5. The apparatus of claim 1, further comprising a collimator which collimates the light emitted from the at least one point light source into a substantially parallel beam so that the light is incident on the hologram pattern at an azimuth angle for which diffraction efficiency is the highest.

6. The apparatus of claim 1, wherein the hologram pattern is configured such that density of the hologram pattern increases away from the at least one point light source to provide uniform intensity distribution of light exited from the top surface of the LGP.

7. The apparatus of claim 1, wherein the configuration of the side of the LGP facing the at least one point light source comprises:

a refracting element which refracts the light emitted from the at least one point light source so that the light is incident obliquely on the hologram pattern.

8. The apparatus of claim 7, wherein the refracting element is a refracting lens disposed on the side of the LGP facing the at least one point light source.

9. The apparatus of claim 8, wherein the refracting lens has a higher refractive index than the LGP.

10. The apparatus of claim 1, further comprising a hologram pattern which is formed on a bottom surface of the LGP, wherein

the top surface of the LGP reflects a remaining portion of the incident light;

and

at least a portion of the remaining portion of the incident light exits from the bottom surface of the LGP.

11. The apparatus of claim 10, further comprising:

a reflector which reflects the at least a portion of the remaining portion of the incident light exiting out of the bottom surface of the LGP onto the top surface of the LGP.

12. The apparatus of claim 10, wherein the side of the LGP facing the at least one point light source is further configured to split the light emitted from the at least one point light source so that:

each of the split lights is incident obliquely on the top and bottom surfaces of the LGP, respectively;

at least a portion of each of the split lights exits from the top and bottom surfaces of the LGP, respectively; and

a remaining portion of each of the split lights is reflected from the top and bottom surfaces of the LGP, respectively.

13. The apparatus of claim 12, further comprising a reflector reflecting the at least a portion of each of the split lights exiting from the bottom surface of the LGP onto the top surface of the LGP.

14. The apparatus of claim 12, further comprising a refracting element which splits the light emitted from the at least one point light source.

15. The apparatus of claim 14, wherein the refracting element comprises:

a first refracting element which refracts a portion of the light emitted from the at least one point light source toward the top surface of the LGP; and

a second refracting element which refracts a portion of the light emitted from the at least one point light source toward the bottom surface of the LGP.

16. The apparatus of claim 15, wherein the first and second refracting elements are parallel to and face each other.

17. The apparatus of claim 16, wherein the first and second refracting elements are integrated with the LGP.

18. The apparatus of claim 12, wherein the side of the LGP facing the at least one point light source comprises:

an upper half which is cut inwardly from the top to the center of the LGP so that one of the split lights is incident obliquely on the top surface of the LGP; and

a lower half which is cut inwardly from the bottom to the center of the LGP so that one of the split lights is incident obliquely on the bottom surface of the LGP.

19. A method for illuminating an LCD backlight, the method comprising:

emitting light onto a side of a light guide place (LGP) comprising a hologram pattern on a top surface thereof so that the light is incident obliquely on the hologram pattern; and

exiting at least a portion of the incident light from the top surface of the LGP through the hologram pattern.

20. The method of claim 19, wherein the light is obliquely incident on the hologram pattern with an altitude angle which provides the highest diffraction efficiency.

21. A method of claim 19, further comprising:

disposing another hologram pattern on the bottom surface of the LGP;

reflecting a remaining portion of the incident light from the top surface of the LGP; and

exiting at least a portion of the remaining portion of the incident light from the bottom surface of the LGP through the other hologram pattern.

22. A method of claim 21, further comprising:

reflecting the at least a portion of the remaining portion of the incident light exiting from the bottom surface of the LGP onto the top surface of the LGP.

23. A method of claim 21, further comprising:

splitting the light emitted onto the one side of the LGP so that each of the split lights is incident obliquely on the top and bottom surfaces of the LGP, respectively;

exiting at least a portion of each of the split lights from the top and bottom surfaces of the LGP, respectively; and

reflecting a remaining portion of each of the split lights from the top and bottom surfaces of the LGP, respectively.

24. A method of claim 23, further comprising:

reflecting the at least a portion of each of the split lights exiting from the bottom surface of the LGP onto the top surface of the LGP.