DISPLAY BACKLIGHTS WITH ADJUSTABLE NARROW VIEWING ANGLE

• US 20110317399A1
• Filed: 06/24/2010
• Published: 12/29/2011
• Est. Priority Date: 06/24/2010
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Hsu, Feng-Hsiung
• Granted Patent: US 9,348,160 B2
• Time in Patent Office: Days
• US Class Current: 362/97.1
• CPC Class Codes: G02F 1/1323 Arrangements for providing a switchable viewing angle
• CPC Class Codes: G02F 1/133 Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements arrangements or circuits for control of liquid crystal elements in a matrix, not structurally associated with these elements G09G3/36
• 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
• CPC Class Codes: G02F 2203/62 Switchable arrangements whereby the element being usually not switchable

Abstract

Display components (e.g., liquid crystal displays (LCDs)) are viewable at different viewing angles, such as by a first user positioned directly in front of the display and by a second user positioned to one side of the display. Many displays present a consistent display across a wide range of viewing angles, but these displays may consume energy and/or compromise user privacy. Presented herein are configurations of backlights for display devices featuring an adjustable viewing angle, such that a user may select a narrower viewing angle in usage scenarios involving power consumption or privacy, and may select a wider viewing angle in usage scenarios involving plentiful power and fewer privacy concerns. Such configurations may include multiple banks of backlight lamps generating backlight at different viewing angles; an electrowetting electrode as an adjustable collimator; adjustable diffusers that may adjustably scatter light passing therethrough; and/or a combination of such adjustable elements.

Claims

1. A backlight for a display surface, comprising:

at least one wide-beam lamp configured to emit light at a wide angle;

at least one narrow-beam lamp configured to emit light at a narrow angle directed toward the display surface;

a light angle selector configured to activate one of the at least one wide-beam lamp and the at least one narrow-beam lamp;

an optical coupler positioned between at least one lamp and the display surface and configured to couple the light with the display surface; and

an optical light guide positioned between at least one lamp and the display surface and configured to distribute the light across the display surface.

2. The backlight of claim 1:

the backlight comprising at least one moderate-beam lamp configured to emit light at an angle less than the wide angle of the wide-beam lamp and greater than the narrow angle of the narrow-beam lamp; and

the light angle selector configured to activate one of the at least one wide-beam lamp, the at least one moderate-beam lamp, and the at least one narrow-beam lamp.

3. The backlight of claim 1, comprising:

a forward polarizer positioned between at least one lamp and the display surface and configured to transmit light having a light polarity approximately equal to a desired light polarity.

4. The backlight of claim 3, the forward polarizer comprising a reflective forward polarizer configured to reflect backwardly light having a light polarity not approximately equal to a desired light polarity.

5. The backlight of claim 4, the reflective forward polarizer comprising a wire grid polarizer.

6. The backlight of claim 4, the reflective forward polarizer comprising an interference reflector composed of a biaxial film.

7. The backlight of claim 1, comprising:

a back reflector positioned around at least one lamp and configured to reflect light toward the display surface.

8. A backlight for a display surface, comprising:

at least one lamp emitting light;

an optical coupler positioned between at least one lamp and the display surface and configured to couple the light with the display surface;

an optical light guide positioned between at least one lamp and the display surface and configured to distribute the light across the display surface; and

an adjustable collimator positioned between the optical light guide and the display surface and configured to align the light toward the display surface with a collimation angle of the light emitted by the at least one lamp, the collimation angle adjustable between a zero-degree collimation angle and a nonzero-degree collimation angle inversely proportional to a collimation magnitude.

9. The backlight of claim 8, the adjustable collimator comprising an electrowetting electrode providing an adjustable collimation angle proportional to an electrowetting voltage applied to the electrowetting electrode.

10. The backlight of claim 9, comprising:

a light angle selector configured to apply to the electrowetting electrode an electrowetting voltage selected from at least three electrowetting voltages respectively producing a collimation angle.

11. The backlight of claim 8, the adjustable collimator comprising:

a collimator positioned between the optical light guide and the display surface and configured to align the light toward the display surface with a collimation angle less than an angle of light emitted by the optical light guide; and

an adjustable diffuser positioned between the collimator and the display surface and configured to diffuse the light proportional to a diffuser voltage applied to the adjustable diffuser.

12. The backlight of claim 11, the adjustable diffuser comprising a polymer-dispersed liquid crystal.

13. The backlight of claim 11, the adjustable diffuser comprising a polymer-stabilized cholesteric texture.

14. The backlight of claim 11, comprising:

a light angle selector configured to apply to the adjustable diffuser a diffuser voltage selected from at least three diffuser voltages respectively producing a collimation angle.

15. The backlight of claim 8, comprising:

a forward polarizer positioned between at least one lamp and the display surface and configured to transmit light having a light polarity approximately equal to a desired light polarity.

16. The backlight of claim 15, the forward polarizer comprising a reflective forward polarizer configured to reflect backwardly light having a light polarity not approximately equal to a desired light polarity.

17. The backlight of claim 16, the reflective forward polarizer comprising a wire grid polarizer.

18. The backlight of claim 16, the reflective forward polarizer comprising an interference reflector composed of a biaxial film.

19. The backlight of claim 8, comprising:

a back reflector positioned around at least one lamp and configured to reflect light toward the display surface.

20. A backlight for a display surface, comprising:

at least one wide-beam lamp configured to emit light at a wide angle;

at least one narrow-beam lamp configured to emit light at a narrow angle directed toward the display surface;

at least one first light angle selector configured to activate one of the at least one wide-beam lamp and the at least one narrow-beam lamp;

an optical coupler positioned between at least one lamp and the display surface and configured to couple the light with the display surface;

an optical light guide positioned between at least one lamp and the display surface and configured to distribute the light across the display surface;

an adjustable collimator positioned between the optical light guide and the display surface and configured to align the light toward the display surface with a collimation angle of the light emitted by the at least one lamp, the collimation angle adjustable between a zero-degree collimation angle and a nonzero-degree collimation angle inversely proportional to a collimation magnitude, the adjustable collimator comprising an electrowetting electrode providing an adjustable collimation angle proportional to an electrowetting voltage applied to the electrowetting electrode;

a second light angle selector configured to apply to the electrowetting electrode an electrowetting voltage selected from at least three electrowetting voltages respectively producing a collimation angle;

an adjustable diffuser positioned between the collimator and the display surface and configured to diffuse the light proportional to a diffuser voltage applied to the adjustable diffuser, the adjustable diffuser selected from a set of adjustable diffusers comprising;

a polymer-dispersed liquid crystal, and

a polymer-stabilized cholesteric texture;

a third light angle selector configured to apply to the adjustable diffuser a diffuser voltage selected from at least three diffuser voltages respectively producing a collimation angle;

a forward polarizer positioned between at least one lamp and the display surface and configured to transmit light having a light polarity approximately equal to a desired light polarity, the forward polarizer comprising a reflective forward polarizer configured to reflect backwardly light having a light polarity not approximately equal to a desired light polarity, and the forward polarizer selected from a set of forward polarizers comprising;

a wire grid polarizer, and

an interference reflector composed of a biaxial film; and

a back reflector positioned around at least one lamp and configured to reflect light toward the display surface.