Display backlights with adjustable narrow viewing angle
Display components (e.g., liquid crystal displays (LCDs)) are viewable at different viewing angles, for example, 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.
1. A backlight for a display surface providing an adjustable viewing angle of light emitted by the display surface that is selectable by a user, the backlight comprising:
at least one wide-beam lamp configured to emit light at a wide angle directed toward the display surface;
at least one narrow-beam lamp configured to emit light at a narrow angle directed toward the display surface, wherein the narrow angle is less than the wide angle;
a light angle selector having a wide viewing angle setting and a narrow viewing angle setting, for setting a viewing angle of the light emitted by the display surface, and configured to:
power the at least one wide-beam lamp in response to a selection by the user of the wide viewing angle setting while leaving the at least one narrow beam lamp unpowered, and
power the at least one narrow-beam lamp in responses to a selection by the user of the narrow viewing angle setting while leaving the at least one wide-beam lamp unpowered;
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 , further 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 , further 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 providing an adjustable viewing angle of light emitted by the display surface that is selectable by a user, comprising:
at least one lamp configured to emit light;
an optical coupler positioned between the at least one lamp and the display surface and configured to couple the light with the display surface;
an optical light guide positioned between the 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, responsive to a selection by the user of a selected adjustable viewing angle setting of the light emitted by the display surface, 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 according to the selected viewing angle setting selected by the user; 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.
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 , further 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 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.
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 , further 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 , further 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 , further comprising: a back reflector positioned around at least one lamp and configured to reflect light toward the display surface.
20. An electronic device comprising a backlight for a display surface providing an adjustable viewing angle of light emitted by the display surface that is selectable by a user, the backlight 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 having a wide viewing angle setting and a narrow viewing angle setting, for setting a viewing angle of light emitted by the display surface, and configured to power:
the at least one wide-beam lamp responsive to a selection by the user of the wide viewing angle setting of the light emitted by the display surface, while leaving the at least one narrow beam lamp unpowered; and
the at least one narrow-beam lamp responsive to a selection by the user of the narrow viewing angle setting of the light emitted by the display surface while leaving the at least one wide-beam lamp unpowered;
an optical coupler positioned between at least one lamp and the display surface and configured to couple the light with the display surface;
a solid optical light guide positioned between at least one of the at least one wide-beam lamp and the at least one narrow-beam 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 of the at least one wide-beam lamp and the at least one narrow-beam 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 according to a selected viewing angle setting received from the user;
a second light angle selector configured to apply to the electrowetting electrode an electrowetting voltage selected according to the selected viewing angle setting 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, where the diffuser voltage is selected according to the selected viewing angle setting received from the user;
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 according to the selected viewing angle setting received from the user, 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.