SURFACE ILLUMINATION APPARATUS AND LIQUID CRYSTAL DISPLAY

• US 20080192173A1
• Filed: 02/14/2008
• Published: 08/14/2008
• Est. Priority Date: 02/14/2007
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Kadowaki, Shinichi, Shikii, Shinichi, Itoh, Tatsuo, Mizushima, Tetsuro, Yamamoto, Kazuhisa, Nagata, Takayuki
• Granted Patent: US 7,740,392 B2
• Time in Patent Office: Days
• US Class Current: 349/61
• CPC Class Codes: G02B 6/0016 Grooves, prisms, gratings, scattering particles or rough surfaces
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses
• CPC Class Codes: G02F 1/133621 providing coloured light G02F1/133617, G02F1/133533 take precedence
• CPC Class Codes: G02F 1/133622 Colour sequential illumination

Abstract

A surface illumination apparatus is provided which includes a laser light source and a light guide plate upon which a laser beam emitted from the laser light source is incident through an end-surface portion and from which the laser beam is emitted through a main-surface portion on one side thereof. The laser beam is incident through an end-surface portion at an inclination angle to a main-surface portion on the other side which faces the one main-surface portion of the light guide plate, undergoes a change in the optical-path direction thereof by the other main-surface portion, is incident on the one main-surface portion and is emitted as a substantially parallel beam from the one main-surface portion.

Claims

1. A surface illumination apparatus, comprising:

a laser light source which emits a substantially parallel laser beam; and

a light guide plate which includes first and second main-surface portions and a first end-surface portion located in an end part of the first and second main-surface portions,

wherein a laser beam emitted from the laser light source;

is incident at an inclination angle to the first main-surface portion upon the first end-surface portion;

is incident on the second main-surface portion after the direction of an optical path thereof is changed by the first main-surface portion; and

is emitted as a substantially parallel beam with kept polarized from the second main-surface portion.

2. The surface illumination apparatus according to claim 1, wherein:

the first main-surface portion inclines in the direction where the light guide plate becomes thinner from the first end-surface portion toward a second end-surface portion opposite to the first end-surface portion;

the first main-surface portion is formed with a plural of first curved-surface portions from the first end-surface portion toward the second end-surface portion, and the first curved-surface portion reflects the laser beam incident on the first end-surface portion toward of the second main-surface portion;

the second main-surface portion is formed with a plural of second curved-surface portions in the position corresponding to the plural of first curved-surface portions from the first end-surface portion toward the second end-surface portion, and the second curved-surface portion has a curvature for emitting the laser beam reflected by the first curved-surface portion as a substantially parallel beam from the second main-surface portion; and

the laser beam incident on the first end-surface portion is emitted as a substantially parallel beam from the second main-surface portion after the direction of the optical path thereof is changed by the first and second curved-surface portions.

3. The surface illumination apparatus according to claim 2, wherein:

the first curved-surface portion includes a continuous curved surface which reflects the incident laser beam so that this laser beam is incident on the whole surface of the second curved-surface portion;

the second curved-surface portion is shaped like a lens whose focal point coincides with the intersection point of the optical axes of the laser beams reflected by the first curved-surface portion; and

the laser beam reflected by the first curved-surface portion is emitted as a substantially parallel beam in a substantially perpendicular direction to the second main-surface portion after the direction of the optical path thereof is changed by the second curved-surface portion.

4. The surface illumination apparatus according to claim 1, wherein:

the thickness between the first main-surface portion and the second main-surface portion is substantially constant;

the first main-surface portion is formed with a first diffraction grating which has a lattice vector in the direction where the laser beam incident on the first end-surface portion advances;

the second main-surface portion is formed with a second diffraction grating which further diffracts the beam diffracted by the first diffraction grating and emits this beam as a substantially parallel beam; and

the laser beam incident on the first end-surface portion is emitted as a substantially parallel beam from the second main-surface portion after diffracted by the first diffraction grating and the second diffraction grating.

5. The surface illumination apparatus according to claim 4, wherein:

the laser light source emits a laser beam formed by combining a red light, a green light and a blue light;

the first diffraction grating separates the combined laser beam into each color and reflects the red light in a first direction, the green light in a second direction different from the first direction and the blue light in a third direction different from the first and second directions; and

the second diffraction grating;

has a pitch substantially equal to the first diffraction grating;

diffracts the red light incident in the first direction, the green light incident in the second direction and the blue light incident in the third direction; and

emits each beam as a substantially parallel beam.

6. The surface illumination apparatus according to claim 4, further comprising an optical-path change member which changes the optical path of the laser beam emitted from the second main-surface portion in a substantially perpendicular direction to the second main-surface portion.

7. The surface illumination apparatus according to claim 1, wherein:

the first main-surface portion inclines in the direction where the light guide plate becomes thinner from the first end-surface portion toward a second end-surface portion opposite to the first end-surface portion;

the first main-surface portion is formed with a diffraction grating which has a lattice vector in the direction where the laser beam incident on the first end-surface portion advances; and

the laser beam incident on the first end-surface portion is emitted as a substantially parallel beam from the second main-surface portion after the direction of the optical path thereof is changed by the diffraction grating.

8. The surface illumination apparatus according to claim 7, wherein:

the laser light source emits a laser beam formed by combining a red light, a green light and a blue light;

a color separation member is further provided which separates the combined laser beam into each color and emits the red light in a first direction, the green light in a second direction different from the first direction and the blue light in a third direction different from the first and second directions; and

the diffraction grating diffracts the red light incident in the first direction, the green light incident in the second direction and the blue light incident in the third direction, and emits each beam in a substantially perpendicular direction to the second main-surface portion.

9. The surface illumination apparatus according to claim 1, further comprising a first laser-beam scan portion which scans the laser beam incident on the first end-surface portion in the thickness directions of the light guide plate.

10. The surface illumination apparatus according to claim 9, further comprising:

a second laser-beam scan portion which scans the laser beam scanned by the first laser-beam scan portion in the longitudinal directions of the first end-surface portion;

an optical conversion member which converts the laser beam scanned by the second laser-beam scan portion into a substantially parallel beam; and

a turning-back member which turns back the substantially parallel beam formed after the conversion by the optical conversion member and guides this substantially parallel beam to the first end-surface portion,

wherein the laser light source, the first and second laser-beam scan portions, the optical conversion member and the turning-back member are disposed on the first main-surface portion.

11. The surface illumination apparatus according to claim 1, further comprising:

an enlargement member which enlarges a laser beam emitted from the laser light source in the thickness directions of the light guide plate and in the longitudinal directions of the first end-surface portion;

an optical conversion member which converts the laser beam enlarged by the enlargement member into a substantially parallel beam; and

a turning-back member which turns back the substantially parallel beam formed after the conversion by the optical conversion member and guides this substantially parallel beam to the first end-surface portion,

wherein the laser light source, the enlargement member, the optical conversion member and the turning-back member are disposed on the first main-surface portion.

12. The surface illumination apparatus according to claim 1, wherein:

the laser light source includes a plurality of light sources having at least light sources which emit beams with the wavelengths of a red light, a green light and a blue light, and a laser combining portion which combines the beams emitted from the plurality of light sources; and

a beam with a plurality of wavelengths combined by the laser combining portion is incident on the first end-surface portion.

13. A liquid crystal display, comprising:

a liquid-crystal display panel; and

a backlight unit which illuminates the liquid-crystal display panel, wherein;

the backlight unit is formed by the surface illumination apparatus according to claim 1; and

the surface illumination apparatus and the liquid-crystal display panel are arranged so that the polarization-axis angle of a laser beam emitted from the surface illumination apparatus becomes a predetermined angle with respect to the polarization-axis angle of a polarizing plate disposed on the view side of the liquid-crystal display panel.

14. The liquid crystal display according to claim 13, wherein the liquid-crystal display panel is not provided with a polarizing plate between the surface illumination apparatus and the liquid-crystal display panel, and a laser beam emitted from the surface illumination apparatus is incident without passing through the polarizing plate upon the liquid-crystal display panel.

15. The liquid crystal display according to claim 14, wherein:

a laser beam emitted from the surface illumination apparatus includes at least a red light, a green light and a blue light;

the lights of these colors are switched one after another at a switching interval set within a one-field period in the image display of the liquid-crystal display panel; and

the liquid-crystal display panel is driven in synchronization with the switching time.