Display apparatus having collimated illumination

• US 20060227259A1
• Filed: 04/08/2005
• Published: 10/12/2006
• Est. Priority Date: 04/08/2005
• Status: Active Grant

• Current Assignee: SKC Hi-Tech & Marketing Co., Ltd.
• Original Assignee: Eastman Kodak Company
• Inventors: Kessler, David, Ishikawa, Tomohiro, Mi, Xiang-Dong
• Granted Patent: US 7,295,262 B2
• Time in Patent Office: Days
• US Class Current: 349/61
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses

Abstract

A display apparatus (30) has an LC device (14) exhibiting its maximum contrast with incident light at an oblique angle φ from normal, wherein oblique angle φ is greater than about +/−10 degrees from normal. A backlight unit (32) provides substantially collimated illumination with a central ray at an incident angle θ₂ with respect to the LC device (14), wherein incident angle θ₂ within about +/−5 degrees of oblique angle φ. The full-width half-maximum intensity of the illumination is within about +/−10 degrees of the central ray at incident angle θ₂.

Claims

1. A display apparatus comprising:

(a) an LC device exhibiting its maximum contrast with incident light at an oblique angle φ

from normal, wherein oblique angle φ

is greater than about +/−

10 degrees from normal; and

,

(b) a backlight unit providing substantially collimated illumination with a central ray at an incident angle θ

₂ with respect to the LC device, wherein incident angle θ

₂ is within about +/−

5 degrees of oblique angle φ and

wherein the full-width half-maximum intensity of the illumination is within about +/−

10 degrees of the central ray at incident angle θ

₂.

2. The display apparatus of claim 1 further comprising a diffuser disposed to diffuse light modulated by the LC device.

3. The display apparatus of claim 1 wherein the backlight unit comprises

(a) a light source;

(b) a light guiding plate for emitting a collimated light at a first oblique angle with respect to the surface of the LC device; and

,

(c) a light redirecting film for redirecting the collimated light at incident angle θ

₂ toward oblique angle φ

.

4. The display apparatus of claim 1 wherein the backlight unit comprises

(a) at least one light source;

(b) a light providing surface for providing an output light supplied by the at least one light source;

(c) a collimating element for collimating the output light toward oblique angle φ

.

5. The display apparatus of claim 1 wherein the LC device is a twisted nematic device.

6. The display apparatus of claim 1 wherein the LC device is an optically compensated birefringence device.

7. The display apparatus of claim 1 wherein oblique angle φ

is between about +/−

25 and +/−

10 degrees from normal.

8. The display apparatus of claim 4 wherein the collimating element comprises asymmetrical optical structures.

9. The display apparatus of claim 4 wherein the collimating element is a film.

10. The display apparatus of claim 1 wherein the LC device is a vertically aligned device.

11. The display apparatus of claim 1 wherein the LC device is an in-plane switching device.

12. A method for forming an image comprising:

(a) providing an LC device exhibiting its maximum contrast with incident light at an oblique angle φ

from normal, wherein oblique angle φ

is greater than about +/−

10 degrees from normal; and

,

(b) directing a substantially collimated illumination as incident light to the LC device, with a central ray at an incident angle θ

₂ with respect to the LC device within about +/−

5 degrees of oblique angle φ and

wherein the full-width half-maximum intensity of the illumination is within about +/−

10 degrees of the central ray at incident angle θ

₂.

13. The method of claim 12 wherein the step of providing an LC device comprises the step of providing a twisted nematic LC device.

14. The method of claim 12 wherein oblique angle φ

is between about +/−

10 degrees from normal and +/−

25 degrees from normal.

15. The method of claim 12 wherein directing a substantially collimated illumination comprises the step of disposing a light redirecting film between a light guiding plate and the LC device.

16. The method of claim 12 wherein directing a substantially collimated illumination comprises the step of disposing a collimating film between a light providing surface and the LC device.