Diffuser sheet for compensating for chromatic dispersion and illumination apparatus employing the same

• US 20070081359A1
• Filed: 03/27/2006
• Published: 04/12/2007
• Est. Priority Date: 06/08/2005
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electro-Mechanics Co., Ltd. (Samsung Group)
• Inventors: Choi, Jin-Seung, You, Jae-ho, Lee, Su-mi, Kim, Jin-hwan, Choi, Yoon-sun, Min, Jee-hong
• Granted Patent: US 7,661,868 B2
• Time in Patent Office: Days
• US Class Current: 362/608
• CPC Class Codes: G02B 5/0226 having particles on the surface
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer

Abstract

A diffuser sheet which compensates for chromatic dispersion generated in a hologram light guide plate, and an illumination apparatus employing the diffuser sheet are provided. The diffuser sheet includes a plate type light-transmissive substrate and a light diffusion layer disposed on a light emission surface of the light-emission substrate. A light-incident surface of the light-transmissive substrate has declined surfaces and flat surfaces which are alternatively and repeatedly formed thereon. The declined surfaces are declined at a predetermined angle.

Claims

1. A diffuser sheet for uniformly diffusing incident light, comprising:

a plate type light-transmissive substrate; and

a light diffusion layer disposed on a light emission surface of the light-transmissive substrate,

wherein a light-incident surface of the light-transmissive substrate has declined surfaces and flat surfaces which are alternatively and repeatedly formed; and

wherein the declined surfaces are declined at a predetermined angle.

2. The diffuser sheet of claim 1, wherein the ratios of widths of the declined surfaces to widths of the flat surfaces vary over the light incident surface.

3. The diffuser sheet of claim 1, wherein the light diffusion layer comprises a plurality of non-uniformly sized beads.

4. A diffuser sheet for uniformly diffusing light emitting from an upper surface of a light guide plate disposed adjacent to a light source, comprising:

a light-incident surface facing the light guide plate and having declined surfaces and flat surfaces alternatively and repeatedly arranged which compensate for chromatic dispersion generated when light is emitted through the upper surface of the light guide plate.

5. The diffuser sheet of claim 4, wherein the declined surfaces face the direction from which light is incident on one sidewall surface of the light guide plate.

6. The diffuser sheet of claim 5, wherein the ratios of widths of the declined surfaces to widths of the flat surfaces decrease along the surface of the light incident surface with distance from the sidewall surface of the light guide plate on which light is incident.

7. The diffuser sheet of claim 5, wherein the declined surfaces are declined at a predetermined angle and the predetermined angle is determined such that red and blue light incident on the declined surfaces mixes within the diffuser sheet with red and blue light incident on the flat surfaces.

8. The diffuser sheet of claim 5, wherein a light emission surface of the diffuser sheet comprises a light diffusion layer having a plurality of non-uniformly sized beads.

9. The diffuser sheet of claim 5, wherein the declined surfaces are recesses in the diffuser sheet.

10. An illumination apparatus comprising:

a light source which emits light;

a light guide plate having a first sidewall surface disposed adjacent to the light source, and a hologram pattern formed on an upper surface thereof such that the light emitted from the light source and then incident into the first sidewall surface is emitted through the upper surface thereof; and

a diffuser sheet which uniformly diffuses light emitted from the upper surface of the light guide plate,

wherein a light-incident surface of the diffuser sheet comprises declined surfaces and flat surfaces which are alternatively and repeatedly formed so as to compensate for chromatic dispersion caused by the hologram pattern;

wherein the declined surfaces are declined at a predetermined angle.

11. The illumination apparatus of claim 10, wherein the declined surfaces of the diffuser sheet face the direction from which light is incident on the first sidewall surface of the light guide plate.

12. The illumination apparatus of claim 11, wherein the ratios of widths of the declined surfaces to widths of the flat surfaces decrease along the surface of the light incident surface with distance from the first sidewall surface of the light guide.

13. The illumination apparatus of claim 11, wherein the declined angle of the declined surfaces is a predetermined angle which is determined such that red and blue light incident on the declined surfaces mixes within the diffuser sheet with red and blue light incident on the flat surfaces.

14. The illumination apparatus of claim 11, wherein a light emission surface of the diffuser sheet comprises a light diffusion layer having a plurality of non-uniformly sized beads.

15. The illumination apparatus of claim 11, wherein the light source is a white light LED.

16. The illumination apparatus of claim 11, further comprising a light reflective plate disposed adjacent to a second sidewall surface opposing the first sidewall surface of the light guide plate;

wherein the light reflective plate reflects light emitted from the second sidewall surface of the light guide plate, back toward the second sidewall surface of the light guide plate.

17. The illumination apparatus of claim 11, wherein the declined surfaces are recesses in the diffuser sheet.

18. A diffuser sheet, comprising:

a substantially planar light-transmissive substrate having a light emission surface and a light incident surface;

a light diffusion layer disposed on the light emission surface of the substrate;

wherein the light incident surface comprises a plurality of declined surfaces and flat surfaces, where the declined surfaces and the flat surfaces are arranged alternately; and

wherein the declined surfaces are declined at a predetermined angle.

19. An illumination apparatus, comprising:

a light source;

a light guide plate comprising a sidewall adjacent to the light source and an upper surface having a hologram pattern formed thereon; and

a diffuser sheet having a light incident surface disposed adjacent to the upper surface of the light guide plate;

wherein the light incident surface of the diffuser sheet comprises a plurality of declined surfaces and flat surfaces, where the declined surfaces and the flat surfaces are arranged alternately; and

wherein the declined surfaces are declined at a predetermined angle.