Surface light source device with polarization function

• US 6,172,809 B1
• Filed: 08/03/1998
• Issued: 01/09/2001
• Est. Priority Date: 03/16/1994
• Status: Expired due to Term

• Current Assignee: Enplas Corporation
• Original Assignee: Enplas Corporation
• Inventors: Arai, Takayuki, Koike, Yasuhiro
• Primary Examiner(s): Nguyen, Thong
• Assistant Examiner(s): CHERRY, EUNCHA P
• Application Number:
  US09/127,822
• Time in Patent Office: 890 Days
• Field of Search: 362/31, 362/19, 349/65, 349/64, 349/66, 353/20, 359/483, 359/485, 359/487
• US Class Current: 359/485.04
• CPC Class Codes: G02B 6/0001 specially adapted for lighting devices or systems lighting or signalling on vehicles using light guides B60Q1/00; lighting devices for vehicle dashboards B60Q3/10; lighting devices for vehicle interior using light guides B60Q3/62; lighting devices mounted on the vehicle rear part using light guides F21S43/235; measuring arrangements having light conducting pointers G01D13/265; illumination of liquid crystal displays G02F1/1336; illuminated signs G09F13/00
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped 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: G02B 6/0065 Manufacturing aspects; Material aspects
• CPC Class Codes: Y10S 385/901 Illuminating or display apparatus

Abstract

Light is supplied into a light incident surface 2 from a fluorescent lamp L enclosed by a silver foil sheet R, and parallelized illuminating light flux is taken out from a light exit surface 3. On a back surface 4 side of a light flux parallelizer 1, across or without a thin air layer 5, a polarization converter Σ is disposed. The polarization converter Σ reinforces the polarization function of the surface light source device through polarization conversion action accompanying reflection in the prism. At a position confronting the light exit surface 3 across an air layer 7, a polarization separating plate 8 is disposed. At a further outside, across an air layer 9, an exit light direction modifier 10 is disposed. A bright polarized illuminating light flux is emitted from a light exit surface 11. When applied to a backlight of a liquid crystal display, a liquid crystal display panel is disposed at a further outside of the exit light direction modifier 10.

Claims

1. A surface light source device with a polarization function comprising:

a light flux parallelizer composed of a plate shaped light scattering light guide having a scattering power uniform throughout the volume of the light scattering light guide and a wedge shaped cross section, the light flux parallelizer having a thicker end side and a light exit surface;

light feed means disposed at the thicker end side of the light flux parallelizer; and

light permeable polarization separating means having reflection characteristics depending on polarization and being disposed to extend along the light exit surface of the light flux parallelizer,

wherein the polarization separating means comprises a polarization separating plate made of a transparent optical material having a refractive index in a range of 1.3 to 2.0,

the polarization separating means receiving light emitted from the light exit surface of the light flux parallelizer, transmitting light having a first polarization and reflecting light having a second polarization, orthogonal to the first polarization to return light having the second polarization to said light scattering light guide so that light having the second polarization has a chance of being converted into light having the first polarization by the uniform scattering power, to be transmitted through said polarization separating plate after impinging again thereupon.

2. A surface light source device with a polarization function comprising:

a light flux parallelizer composed of a plate shaped light scattering light guide having a scattering power uniform throughout the volume of the light scattering light guide and a wedge shaped cross section, the light flux parallelizer having a thicker end side and a light exit surface;

light feed means disposed at the thicker end side of the light flux parallelizer;

light permeable polarization separating means having reflection characteristics depending on polarization and being disposed to extend along the light exit surface of the light flux parallelizer; and

an exit light direction modifier disposed outside of the polarization separating means,

wherein the polarization separating means comprises a polarization separating plate made of a transparent optical material having a refractive index in a range of 1.3 to 2.0,

the polarization separating means receiving light from the light exit surface of the light flux parallelizer, transmitting light having a first polarization and reflecting light having a second polarization, orthogonal to said first polarization to return light having the second polarization to said light scattering light guide so that light having the second polarization has a chance of being converted by the uniform scattering power into light having the first polarization to be transmitted through said polarization separating plate after impinging again thereupon.

3. A surface light source device with a polarization function comprising:

a light flux parallelizer composed of a plate shaped light scattering light guide having a scattering power uniform throughout the volume of the light scattering light guide and a wedge shaped cross section, the light flux parallelizer having a thicker end side and a light exit surface;

light feed means disposed at the thicker end side of the light flux parallelizer; and

light permeable polarization separating means having reflection characteristics depending on polarization and being disposed to extend along the light exit surface of the light flux parallelizer,

wherein the polarization separating means comprises a plurality of polarization separating plates disposed in laminates across an air layer or air layers, each being made of a transparent optical material having a refractive index in a range of 1.3 to 2.0,

the polarization separating means receiving light from the light exit surface of the light flux parallelizer, transmitting light having a first polarization and reflecting light having a second polarization, orthogonal to said first polarization to return light having the second polarization to said light scattering light guide so that light having the second polarization has a chance of being converted by the uniform scattering power into light having the first polarization to be transmitted through said polarization separating plate after impinging again thereupon.

4. A surface light source device with a polarization function comprising:

a light flux parallelizer composed of a plate shaped light scattering light guide having a scattering power uniform throughout the volume of the light scattering light guide and a wedge shaped cross section, the light flux parallelizer having a thicker end side and a light exit surface;

light feed means disposed at the thicker end side of the light flux parallelizer;

light permeable polarization separating means having reflection characteristics depending on polarization and being disposed to extend along the light exit surface of the light flux parallelizer; and

an exit light direction modifier disposed outside of the polarization separating means,

wherein the polarization separating means comprises a plurality of polarization separating plates disposed in laminates across an air layer or air layers, each being made of a transparent material and having a refractive index in a range of 1.3 to 2.0,

the polarization separating means receiving light from the light exit surface of the light flux parallelizer, transmitting light having a first polarization and reflecting light having a second polarization, orthogonal to said first polarization to return light having the second polarization to said light scattering light guide so that light having the second polarization has a chance of being converted by the uniform scattering power into light having the first polarization to be transmitted through said polarization separating plate after impinging again thereupon.

5. A surface light source device with a polarization function comprising:

a light flux parallelizer composed of a plate shaped light scattering light guide having a scattering power uniform throughout the volume of the light scattering light guide and a wedge shaped cross section, the light flux parallelizer having a thicker end side and a light exit surface;

light feed means disposed at the thicker end side of the light flux parallelizer; and

light permeable polarization separating means having reflection characteristics depending on polarization and being disposed to extend along the light exit surface of the light flux parallelizer,

wherein the polarization separating means comprises a polarization separating plate having a multilayer film made of an optical material having a refractive index in a range of 1.3 to 2.0,

the polarization separating means receiving light from the light exit surface of the light flux parallelizer, transmitting light having a first polarization and reflecting light having a second polarization, orthogonal to said first polarization to return light having the second polarization to said light scattering light guide so that light having the second polarization has a chance of being converted by the uniform scattering power into light having the first polarization to be transmitted through said polarization separating plate after impinging again thereupon.

6. A surface light source device with a polarization function comprising:

a light flux parallelizer composed of a plate shaped light scattering light guide having a scattering power uniform throughout the volume of the light scattering light guide and a wedge shaped cross section, the light flux parallelizer having a thicker end side and a light exit surface;

light feed means disposed at the thicker end side of the light flux parallelizer;

light permeable polarization separating means having reflection characteristics depending on polarization and being disposed to extend along the light exit surface of the light flux parallelizer; and

an exit light direction modifier disposed outside of the polarization separating means,

wherein the polarization separating means comprises a polarization separating plate having a multilayer film made of an optical material having a refractive index in a range of 1.3 to 2.0,

the polarization separating means receiving light from the light exit surface of the light flux parallelizer, transmitting light having a first polarization and reflecting light having a second polarization, orthogonal to said first polarization to return light having the second polarization to said light scattering light guide so that light having the second polarization has a chance of being converted by the uniform scattering power into light having the first polarization to be transmitted through said polarization separating plate after impinging again thereupon.

7. A surface light source device comprising:

a wedge shaped light guide having a scattering power uniform throughout the volume of the light guide, the light guide having a thicker end side and a light exit surface;

a light source positioned along the thicker end side of the light guide; and

a polarization separating plate made of a transparent optical material having a refractive index in a range of 1.3 to 2.0, the polarization separating plate extending along the light exit surface of the light guide to receive light emitted from the light exit surface of the light guide, transmit light having a first polarization and reflect light having a second polarization, orthogonal to the first polarization so that light having the second polarization is returned to said light guide and has a chance of being converted into light having the first polarization by the scattering power, to be transmitted through said polarization separating plate after impinging again thereupon.