Optical devices using reflecting polarizing materials

• US 6,829,071 B2
• Filed: 05/31/2001
• Issued: 12/07/2004
• 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: Cross, Elisa M., Tabar, Ronald J., Allen, Richard C.
• Primary Examiner(s): Shafer, Ricky D.
• Application Number:
  US09/871,130
• Publication Number:
  US 20010036013A1
• Time in Patent Office: 1,286 Days
• Field of Search: 362/31, 362/19, 362/558, 362/561, 359/246, 359/247, 359/252, 359/253, 359/256, 359/487, 359/495, 359/500, 359/599, 349/62, 349/64, 349/65, 349/96
• 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 polarizer 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;

a light cavity adapted to provide light to the light modulating layer, the light cavity reflecting of the incident light; and

a diffusely reflecting polarizer, disposed between the light modulating layer and the light cavity, for transmitting a component of the light provided by the light cavity having a first polarization for viewing and diffusely reflecting a component of the light, received from the light cavity, having a second polarization, the polarizer diffusely reflecting the light of the second polarization with a second degree of depolarization greater than the first degree of depolarization to provide light of the first polarization;

wherein at least a portion of the diffusely reflected light of the first polarization is reflected by the light cavity without depolarization toward the diffusely reflecting polarizer for transmission therethrough.

2. The display apparatus of claim 1 further comprising a turning lens disposed to receive low angle light output from the light cavity and redirect the light toward the light modulating layer.

3. The display apparatus of claim 2 wherein the turning lens includes a relatively planar surface on a first side and a structured surface on a second side opposite to the first side.

4. The display apparatus of claim 3 wherein the relatively planar surface of the turning lens faces the diffusely reflecting polarizer and the structured surface of the turning lens faces the light cavity.

5. The display apparatus of claim 1 further comprising a diffusion layer disposed between the diffusely reflecting polarizer and the light modulating layer for diffusing light transmitted by the diffusely reflecting polarizer.

6. The display apparatus of claim 1 wherein the second degree of depolarization is about 25%.

7. A display apparatus, comprising:

a light modulating layer;

a light cavity adapted to provide light to the light modulating layer, the light cavity reflecting incident light with a first degree of depolarization for incident light of a first polarization; and

a diffusely reflecting polarizer, disposed between the light modulating layer and the light cavity, for transmitting a component of the light provided by the light cavity having the first polarization for viewing and diffusely reflecting a component of the light, received from the light cavity, having a second polarization, the polarizer diffusely reflecting the light of the second polarization with a second degree of depolarization greater than the first degree of depolarization to provide light of the first polarization;

wherein the first degree of depolarization for incident light of the first polarization is substantially zero and at least a portion of the diffusely reflected light of the first polarization is reflected by the light cavity without substantial depolarization toward the diffusely reflecting polarizer for transmission therethrough.

8. The display apparatus of claim 7 further comprising a turning lens disposed to receive low angle light output from the light cavity and redirect the light toward the light modulating layer.

9. The display apparatus of claim 8 wherein the turning lens includes a relatively planar surface on a first side and a structured surface on a second side opposite to the first side.

10. The display apparatus of claim 9 wherein the relatively planar surface of the turning lens faces the diffusely reflecting polarizer and the structured surface of the turning lens faces the light cavity.

11. The display apparatus of claim 7 further comprising a diffusion layer disposed between the diffusely reflecting polarizer and the light modulating layer for diffusing light transmitted by the diffusely reflecting polarizer.

12. The display apparatus of claim 7 wherein the second degree of depolarization is about 25%.