Polarized light emitting device for illuminating a display

• US 6,960,010 B2
• Filed: 03/27/2003
• Issued: 11/01/2005
• Est. Priority Date: 03/29/2002
• Status: Expired due to Term

• Current Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Original Assignee: Citizen Electronics Company Limited, Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Inventors: Matsumoto, Kenji, Miyashita, Junji
• Primary Examiner(s): Ward, John Anthony
• Assistant Examiner(s): Negron, Ismael
• Application Number:
  US10/397,213
• Publication Number:
  US 20030184989A1
• Time in Patent Office: 950 Days
• Field of Search: 362/19, 362/23, 362/26, 362/29, 362/31, 362/551, 362/558, 362/559, 362/560, 362/561, 362/257, 362/296, 362/307, 362/308, 362/317, 362/326, 362/327, 362/330, 362/341, 362/800, 362/609, 362/626, 362/600, 362/608, 362/610, 362/615, 362/623, 362/625, 349/1, 349/5, 349/8, 349/9, 349/56, 349/84, 349/96, 349/67, 353/20, 353/22, 353/23, 359/483, 359/485, 359/487, 359/488, 372/27, 372/92, 372/97, 372/106
• US Class Current: 362/609
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one

Abstract

A lighting device has a light source for emitting lighting light for illuminating a display, and a light guide plate for changing the direction of the lighting light to the display. A polarization separation film is provided for separating polarization of the lighting light into P-polarized light and S-polarized light for illuminating the display.

Claims

1. A lighting device comprising:

a light source;

a light guide plate disposed to receive a light emitted from the light source at an end face of the light guide plate, and

the light guide plate comprising a light guide body having a polarization direction modifier formed on a surface of the light guide body, and a polarization split film on the surface of the light guide body which transmits p-polarization components and reflects S-polarization components, wherein the polarization direction modifier and the polarization split film are integral with the light guide body, and a reflector for reflecting the light transmitting in the light guide plate, the reflector formed on the light guide body comprises a plurality of prisms.

2. The lighting device according to claim 1 wherein the polarization split film is positioned in the light guide plate to separate an upper part and a lower part of the light guide plate, and the reflector comprising prisms is formed on the bottom face of the light guide plate and the polarizing direction modifier is positioned in the light guide plate under the polarization split film and above the reflector in the light guide plate, and the light source is disposed to face the lower part of the light guide plate at the end face of the light guide plate.

3. The lighting device according to claim 1 wherein the polarization split film is positioned in the light guide plate to separate an upper part and a lower part of the light guide plate, and the polarization split film is positioned on the underside of the reflector comprising prisms and the polarizing direction modifier is positioned below the polarization split film integral with the reflector in the light guide plate and the light source is disposed to face the upper part of the light guide plate at the end face of the light guide plate.

4. The lighting device according to claim 1 wherein the polarization split film is positioned in the light guide plate to separate an upper part and a lower part of the light guide plate and the polarizing direction modifier is positioned in the upper part of the light guide plate and the reflector comprising prisms is formed on the lower part of the light guide plate and the light source is disposed to face the upper part of the light guide plate at the end face of the light guide plate.

5. The lighting device according to claim 2, 3, or 4 where the polarization direction modifier is a quarter-wave plate.

6. The lighting device according to claim 2, 3, or 4 where the polarization split film uses polarizing characteristics of surface plasmon.