Uniform illumination light emitting device

• US 5,641,219 A
• Filed: 06/07/1995
• Issued: 06/24/1997
• Est. Priority Date: 06/22/1990
• Status: Expired due to Fees

• Current Assignee: Tatsuji Mizobe
• Original Assignee: Tatsuji Mizobe
• Inventors: Mizobe, Tatsuji
• Primary Examiner(s): LEE, Y MY QUACH
• Application Number:
  US08/480,929
• Time in Patent Office: 748 Days
• Field of Search: 362/26, 362/31, 362/223
• US Class Current: 362/623
• CPC Class Codes: G02B 6/0021 for housing at least a part of the light source, e.g. by forming holes or recesses
• CPC Class Codes: G02B 6/0043 provided on the surface of the light guide
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G09F 13/0409 Arrangements for homogeneous illumination of the display surface, e.g. using a layer having a non-uniform transparency arrangements of reflectors G09F13/14
• CPC Class Codes: G09F 13/18 Edge-illuminated signs

Abstract

An illuminating device is disclosed in which light is introduced mainly from a light source provided at a peripheral portion of a light emitting surface thereby illuminating the light emitting surface. The illumination of the light emitting surface is kept uniform irrespective of a shape of the light emitting surface, a type of the light source, a number of light sources and a mounting position of the light sources. The device may be used as a display device.

Claims

1. A light emitting device, comprising:

a light transmissive substrate having a light emitting surface, a rear surface and a plurality of sectors;

a light source for introducing light into said light transmissive substrate;

a light reflector disposed around a peripheral region of said light transmissive substrate, except a region where the light is introduced into the light transmissive substrate, to prevent light from leaking from said peripheral region;

a plurality of light reflective objects disposed on said rear surface of said light transmissive substrate having a distribution such that a density of said light reflective objects in each said sector is inversely proportional to an illuminance of said light within said substrate in each said sector, such that illuminance emitted from said light emitting surface in each said sector is substantially uniform, to thereby provide the light emitting device having substantially uniform illuminance.

2. The light emitting device according to claim 1, wherein said light emitting surface is planar.

3. The light emitting device according to claim 1, wherein said light source is provided in an interior portion of the substrate.

4. The light emitting device according to claim 1, wherein said light reflector is a frame extending around said light transmissive substrate, said frame having a low coefficient of reflectivity, as compared to a reflectivity of a transparent material of said light transmissive substrate.

5. The light emitting device according to claim 1, wherein said light reflective objects are lines.

6. The light emitting device according to claim 1, further comprising a metallic sheet on said rear surface of said light transmissive substrate, said metallic sheet including said light reflective objects.

7. A method of forming a light emitting device having a lamp, a light emitting surface and a rear surface, said method comprising the steps of:

forming a substantially uniform pattern of light reflecting objects on said rear surface;

introducing light into said light emitting device;

dividing said light emitting surface into a plurality of areas;

measuring an illuminance of each of said plurality of areas; and

adjusting the illuminance of each of said plurality of areas by varying a density of said light reflective objects on said rear surface in each of said plurality of areas to thereby produce said light emitting device having substantially uniform illuminance.

8. The method as claimed in claim 7, wherein said adjusting step includes adding said light reflective objects to said areas, wherein said light reflective objects include at least one of dot patterns and line patterns, with said dot patterns and line patterns being at least one of coated, printed and formed on said rear surface opposite to said light emitting surface.