Optical devices using reflecting polarizing materials

• US 6,515,785 B1
• Filed: 04/22/1999
• Issued: 02/04/2003
• Est. Priority Date: 04/22/1999
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Cobb, Sanford Jr., Wortman, David L.
• Primary Examiner(s): Shafer, Ricky D.
• Application Number:
  US09/298,003
• Time in Patent Office: 1,384 Days
• Field of Search: 359/247, 359/256, 359/487, 359/495, 359/500, 359/599, 385/36, 385/146, 385/901, 349/62, 349/64, 349/96, 362/19, 362/31, 362/558, 362/559, 362/561
• US Class Current: 359/247
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 5/0236 the diffusion taking place within the volume of the element
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02B 5/0284 used in reflection
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid
• CPC Class Codes: G02B 5/3041 comprising multiple thin layers, e.g. multilayer stacks
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• 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 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: Y10S 385/901 Illuminating or display apparatus

Abstract

Optical devices using reflective polarizers and, in particular, diffusely reflective polarizers are provided. Many of the optical devices utilize the diffusely reflecting and specularly transmitting properties of diffusely reflecting polarizers to enhance their optical characteristics. The optical devices include a lighting system which uses a reflector formed from a diffusely reflecting polarizer attached to a specular reflector. Another optical device is a display apparatus which uses a diffusely reflecting polarizer layer in combination with a turning lens which folds shallow angle light toward a light modulating layer. Other optical devices exploit the depolarizing characteristics of a diffusely reflecting polaizer when reflecting light. Still other optical devices use diffusely reflecting polarizers to recycle light and improve display illumination.

Claims

1. A display apparatus, comprising:

a light modulating layer having a first surface;

a light cavity for providing light to the light modulating layer;

a light guide disposed to receive the light from the light cavity and output the light at a low angle relative to the first surface of the light modulating layer;

a turning lens disposed to receive the low angle light output from the light guide and redirect the light toward the light modulating layer;

a diffusely reflecting polarizer disposed between the turning lens and the light modulating layer for receiving the redirected light and transmitting a component of the redirected light having a first polarization toward the light modulating layer and diffusely reflecting a component of the redirected light having a second polarization different than the first polarization;

wherein the turning lens comprises a structured surface facing the light guide.

2. The display apparatus of claim 1 wherein the low angle is less than 20 degrees.

3. A display apparatus, comprising:

a light modulating layer having a first surface;

a light cavity for providing light to the light modulating layer;

a light guide disposed to receive the light from the light cavity and output the light at a low angle relative to the first surface of the light modulating layer;

a turning lens disposed to receive the low angle light output from the light guide and redirect the light toward the light modulating layer;

a diffusely reflecting polarizer disposed between the turning lens and the light modulating layer for receiving the redirected light and transmitting a component of the redirected light having a first polarization toward the light modulating layer and diffusely reflecting a component of the redirected light having a second polarization different than the first polarization;

wherein the turning lens includes a relatively planar surface facing the diffusely reflecting polarizer and a structured surface facing the light guide.

4. The display apparatus of claim 3, wherein the low angle is less than 20 degrees.