Mode-switchable backlight, privacy display, and method employing emitter arrays

1. A mode-switchable backlight comprising

a first directional backlight comprising an array of narrow-angle emitters configured to provide narrow-angle emitted light during both a first mode and a second mode; and

a second directional backlight comprising an array of bidirectional emitters configured to provide bidirectional emitted light exclusively during the second mode, the bidirectional emitted light having a bifurcated angular extent that is complementary to an angular range of the narrow-angle emitted light,

wherein a combination of the narrow-angle emitted light and the bidirectional emitted light during the second mode is configured to provide broad-angle emitted light having an angular range that is a summation of the angular range of the narrow-angle emitted light and the bifurcated angular extent of the bidirectional emitted light, and

wherein a bidirectional emitter of the bidirectional emitter array comprises a pair of active optical emitters, a first active optical emitter of the active optical emitter pair being configured to provide a first segment of the bidirectional emitted light and a second active optical emitter of the active optical emitter pair being configured to provide a second segment of the bidirectional emitted light.

2. The mode-switchable backlight of claim 1 , wherein the narrow-angle emitted light is configured to provide illumination exclusively to a first view zone during the first mode, the broad-angle emitted light being configured to provide illumination to a second view zone that includes the first view zone during the second mode.

3. The mode-switchable backlight of claim 1 , wherein a bidirectional emitter of the bidirectional emitter array is aligned with a corresponding narrow-angle emitter of the narrow-angle emitter array, the bidirectional emitter and the corresponding narrow-angle emitter cooperatively providing the broad-angle emitted light during the second mode.

4. The mode-switchable backlight of claim 1 , wherein a narrow-angle emitter of the narrow-angle emitter array comprises an active optical emitter configured to provide the narrow-angle emitted light.

5. The mode-switchable backlight of claim 1 , wherein the first directional backlight is configured to provide the narrow-angle emitted light from a first surface and the second directional backlight is adjacent to a second surface of the first directional backlight opposite to the first surface, the first directional backlight being transparent to the bidirectional emitted light.

6. A mode-switchable privacy display comprising the mode-switchable backlight of claim 1 , the display further comprising an array of light valves configured to modulate the narrow-angle emitted light as a private displayed image during the first mode and to modulate the broad-angle emitted light as a public displayed image during the second mode, a viewing range of the private displayed image being limited by the angular range of the narrow-angle emitted light,

wherein the first mode is a privacy mode and the second mode is a public mode of the mode-switchable privacy display.

7. A mode-switchable privacy display comprising:

a first directional backlight comprising an array of narrow-angle emitters configured to provide narrow-angle emitted light during both a privacy mode and a public mode;

a second directional backlight comprising an array of bidirectional emitters configured to provide bidirectional emitted light exclusively during the public mode, the bidirectional emitted light having a bifurcated angular extent that is complementary to an angular range of the narrow-angle emitted light; and

an array of light valves configured to modulate the narrow-angle emitted light as a private displayed image during the privacy mode and to modulate broad-angle emitted light as a public displayed image during the public mode, the broad-angle emitted light comprising a combination of the narrow-angle emitted light and the bidirectional emitted light during the public mode,

wherein the private displayed image is configured to be visible in a private view zone and the public displayed image is configured to be visible in a public view zone that includes the private view zone, and

wherein a narrow-angle emitter of the narrow-angle emitter array comprise an active optical emitter configured to provide the narrow-angle emitted light, and wherein a bidirectional emitter of the bidirectional emitter array comprises a pair of active optical emitters, a first active optical emitter of the active optical emitter pair being configured to provide a first segment of the bidirectional emitted light and a second active optical emitter of the active optical emitter pair being configured to provide a second segment of the bidirectional emitted light.

8. The mode-switchable privacy display of claim 7 , wherein one or both of the active optical emitter of the narrow-angle emitter and the pair of active optical emitters of the bidirectional emitter comprise a light emitting diode.

9. The mode-switchable privacy display of claim 7 , wherein the first directional backlight is between the second directional backlight and the array of light valves, the first directional backlight being transparent to the bidirectional emitted light.

10. A method of mode-switchable backlight operation, the method comprising:

emitting narrow-angle emitted light using an array of narrow-angle emitters during both a first mode and a second mode using a first directional backlight to illuminate a first view zone;

emitting bidirectional emitted light using an array of bidirectional emitters exclusively during the second mode using a second directional backlight, the bidirectional emitted light having a bifurcated angular extent that is complementary to an angular range of the narrow-angle emitted light; and

combining the narrow-angle emitted light and the bidirectional emitted light during the second mode to provide broad-angle emitted light,

wherein the broad-angle emitted light illuminates a second view zone that includes the first view zone, and

wherein a bidirectional emitter of the bidirectional emitter array comprises a pair of active optical emitters, a first active optical emitter of the active optical emitter pair being configured to provide a first segment of the bidirectional emitted light and a second active optical emitter of the active optical emitter pair being configured to provide a second segment of the bidirectional emitted light.

11. The method of mode-switchable backlight operation of claim 10 , wherein the array of narrow-angle emitters comprises narrow-angle active optical emitters and emitting narrow-angle emitted light comprises activating the narrow-angle active optical emitters of the narrow-angle emitter array.

12. The method of mode-switchable backlight operation of claim 10 , wherein emitting bidirectional emitted light comprises activating the first and second active optical emitters of the active optical emitter pair.

13. The method of mode-switchable backlight operation of claim 10 , further comprising modulating the narrow-angle emitted light and the broad-angle emitted light using an array of light valves to display an image, wherein the displayed image is a private displayed image during the first mode and a public displayed image during the second mode, the private displayed image having a viewing range limited by the angular range of the narrow-angle emitted light,

wherein the private displayed image is visible in the first viewing zone and the public displayed image is visible in the second viewing zone that includes the first viewing zone.