Light source device

• US 4,909,604 A
• Filed: 08/23/1988
• Issued: 03/20/1990
• Est. Priority Date: 08/28/1987
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Sano, Tooru, Kobayashi, Akira
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/235,097
• Time in Patent Office: 574 Days
• Field of Search: 350/345, 350/360, 350/334, 362/31, 362/32, 362/26, 362/347, 362/297
• US Class Current: 349/64
• CPC Class Codes: F21V 7/00 Reflectors for light sources characterised by cooling arrangements F21V29/505
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0071 with elongated shape, e.g. tube
• CPC Class Codes: G02B 6/0083 Details of electrical connections of light sources to drivers, circuit boards, or the like
• CPC Class Codes: G09F 2013/1804 Achieving homogeneous illumination

Abstract

A light source device has a transparent plate having a smoothened front surface and a roughened rear surface. A light source is disposed adjacent to an end face of the transparent plate. The roughened rear surface has a portion which is inclined and curved and disposed adjacent to the end of the transparent plate remote from the light source. A reflecting plate is disposed adjacent to and extends along the roughened rear surface of the transparent plate. The provision of the inclined and curved surface portion assures that the luminance of the light on the smoothened front surface of the transparent plate is substantially uniform over the entire surface area. The inclined and curved surface portion is represented by the following equation,

y=H--(H-h)x.sup.n /L.sup.n

where

y is a distance from the smoothened front surface,

x is a distance from the light source,

L is a length of the transparent plate,

H is the value of y at the end face of the transparent plate,

h is the value of y at x being L, and

n is an arbitrary positive number larger than unity, and

wherein the height of the light source is substantially the same as H.

Claims

1. A light source device including a transparent plate having a first transparent surface, a reflecting plate disposed adjacent to a second surface of said transparent plate opposite to said first transparent surface, and at least one light source disposed adjacent to an end face of said transparent plate, wherein said second surface of said transparent plate includes a surface portion which is inclined and curved, said inclined and curved surface portion being represented by the following equation,

View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)

2. A light source device according to claim 1, wherein said transparent plate is made of a material selected from a group including at least one of a transparent acrylic resin and transparent glass.

3. A light source device according to claim 1, wherein said light source is formed by one of a cold cathode fluorescent lamp, a hot cathode fluorescent lamp and LEDs.

4. A light source device according to claim 1, wherein said first transparent surface of said transparent plate is adjacent to a liquid crystal panel of a liquid crystal display device.

5. A light source device according to claim 4, wherein a light diffusing plate is interposed between said first transparent surface and said liquid crystal display panel.

6. A light source device according to claim 1, wherein a plurality of light sources are disposed adjacent to one end face of said transparent plate.

7. A light source device according to claim 1, wherein at least one additional light source is disposed adjacent to the other end face of said transparent plate and wherein said second surface of said transparent plate is formed by an inclined and curved surface portion which is arranged so that said transparent plate is thinnest at a central point which is most remote from said at least one light source and said at least one additional light source, said inclined and curved surface portion being substantially represented by the equations,

8. A light source device according to claim 1, further including an additional transparent plate associated with said first transparent plate so that the two transparent plates are stacked with the first transparent surface of said first transparent plate being in contact with a transparent surface of said additional transparent plate, said second surface of said first transparent plate being disposed on said reflecting plate and a second surface of said additional transparent plate being adjacent to a liquid crystal display panel of a liquid crystal display device, and wherein the assembly of said two transparent plates has opposite ends respectively associated with a light source.

9. A light source device according to claim 1, wherein said inclined and curved surface portion includes means for exhibiting a reflection directivity, said means for exhibiting enabling said inclined and curved surface portion to compensate for attenuation of light increasing towards an end of said transparent plate remote from said at least one light source, thereby providing a substantially uniform surface illuminator.

10. A light source device according to claim 1, wherein said end face of said transparent plate is a planar surface.