Light source device, display device, terminal device, and optical member

• US 7,621,665 B2
• Filed: 03/27/2006
• Issued: 11/24/2009
• Est. Priority Date: 03/28/2005
• Status: Active Grant

• Current Assignee: NLT Technologies, Ltd.
• Original Assignee: NEC Corporation
• Inventors: Uehara, Shinichi, Imai, Masao
• Primary Examiner(s): Alavi; Ali
• Assistant Examiner(s): CARTER, WILLIAM JOSEPH
• Application Number:
  US11/389,004
• Publication Number:
  US 20060227569A1
• Time in Patent Office: 1,338 Days
• Field of Search: 362600-634
• US Class Current: 362/607
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02F 1/1323 Arrangements for providing a switchable viewing angle
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members

Abstract

In the display device, a light source unit, a louver, a transparent/scattering state switching element, and a transmissive liquid crystal panel are provided in sequence, an optical waveguide and a cone sheet are provided to the light source unit, and a light source is disposed on the side of the optical waveguide. The light-exiting surface of the optical waveguide is made flat, and a tilted surface that is tilted to the side of the light source with respect to the light-exiting surface is formed in a light diffusing surface. A flat plate is provided to the cone sheet, and a plurality of circular cones are arranged two-dimensionally on the light-incident surface of the flat plate. The central axes of the circular cones are parallel to each other. The transparent/scattering state switching element is capable of switching between a state for transmitting incident light and a state for scattering the light. By this configuration, a light source device is obtained having high directivity, high luminance, and no limitations on the mounting position of the light source.

Claims

1. A light source device comprising:

a light source;

a light guiding member having an exit surface,

wherein a reference plane is substantially parallel to the exit surface of the light guiding member, and

wherein the light guiding member receives light from the light source and emits in a first direction which forms a first angle with respect to the reference plane, wherein the first direction is different from a direction in which light is emitted from the light source;

an optical member which receives light emitted from the light guiding member and emits light in a second direction which forms a second angle, different from the first angle, with respect to the reference plane;

a light-direction regulating element, which receives light emitted from the optical member, for regulating a direction of emitted light; and

a transparent/scattering state switching element, which receives light emitted from the light-direction regulating element, capable of switching between a state of transmitting light without scattering, and a state of scattering light;

wherein

the light source is disposed along a light-incident surface of the light guiding member;

the optical member comprises a plurality of optical elements having a projection shape and two-dimensionally arranged in a plurality of rows and columns on a light-incident surface thereof, the plurality of optical elements pointing toward the light guiding member; and

the optical member totally reflecting light that has been emitted from the light guiding member, entered the optical elements, and reached side surfaces of the optical elements, and emitting the light;

thus light that has been transmitted through the optical member has a directivity that is increased in two perpendicular directions in the reference plane.

2. The light source device according to claim 1, wherein the optical member comprises:

substantially planar plate of a transparent material; and

the plurality of optical elements which are disposed on a light-incident surface of the plate, wherein each of the plurality of optical elements comprises a circular cone of a transparent material;

wherein

central axes of the plurality of optical elements are parallel to each other.

3. The light source device according to claim 2, wherein a phase of a spacing of optical elements arranged in at least a first row of optical elements differs from a phase of a spacing optical elements in at least a second row of optical elements.

4. The light source device according to claim 2, wherein the rows and columns of the optical elements are uniformly spaced.

5. The light source device according to claim 2, wherein the central axes of the plurality of optical elements form acute angles with respect the light incident surface of the plate, such that the second direction is orthogonal to the light incident surface of plate.

6. The light source device according to claim 2, wherein the optical member further comprises a diffusion pattern formed on a light exit surface of the plate.

7. The light source device according to claim 1, wherein

the light source comprises a point light source;

and

the light guiding member comprises a diffusion pattern formed on a light incident surface thereof.

8. The light source device according to claim 1, wherein

the light guiding member comprises an optical waveguide comprising the light exit surface, a lateral light incident face, and a surface opposite the light exit surface, and

the surface opposite the light exit face includes a tilted surface, a plane of which forms an acute angle with respect to the reference plane.

9. The light source device according to claim 1, further comprising a reflecting sheet disposed on a surface of the light guiding member, opposite the light exit surface.

10. The light source device according to claim 1, wherein

the light-direction regulating element comprises transparent areas, which transmit light incident thereon, and absorbent areas, which absorb light incident thereon;

the transparent areas and the absorbent areas are alternately disposed in a direction parallel to the reference plane; and

wherein light emitted from the light-direction regulating element has a directivity, in a direction orthogonal to the reference plane, greater than a directivity of light incident on the light-direction regulating element.

11. The light source device according to claim 10, wherein the light-direction regulating element comprises a first layer and a second layer, wherein an arrangement direction of the transparent areas and the absorbent areas in the first layer is orthogonal to an arrangement direction of the transparent areas and the absorbent areas in the second layer.

12. The light source device according to claim 10, wherein the transparent areas comprise discreet areas, surrounded by the absorbent areas, arranged in a matrix as viewed from the direction orthogonal to the reference plane.

13. The light source device according to claim 12, wherein the discreet areas are one of circular, elliptical, square, and rectangular, as viewed from the direction orthogonal to the reference plane.

14. The light source device according to claim 10, wherein the boundaries wherein a thickness of a transparent area meets a thickness of an absorbent area are parallel to the second direction.

15. The light source device according to claim 10, wherein the transparent areas are arranged in rows and columns, and the rows and columns of the transparent areas form acute angles with respect to the rows and columns of the optical elements.

16. The light source device according to claim 1, wherein the light-direction regulating element is integrally formed with optical member.

17. The light source device according to claim 1, wherein the light source is disposed along the light-incident surface of the light guiding member.

18. The light source device according to claim 17, wherein the light source is a cold cathode tube.

19. A display device comprising:

the light source according to claim 1; and

a display panel which receives light incident from the light source and form an image therewith.

20. The display device according to claim 19, wherein pixels of the display panel are arranged in rows and columns which form acute angles with respect to the rows and columns of the optical elements.

21. The display device according to claim 19, wherein the display panel is a liquid crystal panel.

22. The display device according to claim 21, wherein the liquid crystal panel operates on a lateral field principle, a multi-domain vertical alignment principle, or a film-compensated TN principle.

23. A terminal device comprising the display device according to claim 19.

24. The terminal device according to claim 23, comprising a mobile telephone, a personal information terminal, a gaming device, a digital camera, a video camera, a video player, a notebook-type personal computer, a cash dispenser, or a vending machine.

25. The terminal device according to claim 24 comprising a mobile telephone, wherein the light source is disposed above or below the display screen, as viewed by a user.

26. A light source device comprising:

a light source for emitting diffused light;

a light-guiding plate having a side surface on which light from the light source is incident, and having a light-exiting surface, and a light-diffusing surface opposite the light-exiting surface, wherein;

the side surface of the light guiding plate is spaced from the light source in a +X direction, and wherein the light-exiting surface is substantially planar in an X-Y plane;

the light-diffusing surface comprises a slanted portion, an outer surface of which is tilted towards a +X direction;

an optical member which receives light output from the light guiding plate, the optical member comprising a plurality of projections arranged in a plurality of rows and columns on a light-incident surface thereof, facing the light-exiting surface of the light-guiding plate, wherein light is totally internally reflected at interior side surfaces of the projections and directed to a light-exiting surface of the optical member, thus narrowing a range of angles, in the Y direction, over which light is output from the optical member;

a light-direction regulating element which receives light output from the optical member, the light-direction regulating element modifying a diffusion, in a Y direction, of emitted light; and

a transparent/scattering state switching element having a light incident surface on which light from the light-direction regulating element is incident, the transparent/scattering state switching element capable of switching between a first state of transmitting, without scattering, light incident from the light-direction regulating element, and a second state of scattering light incident from the light-direction regulating element.