Wide angle imaging directional backlights
An imaging directional backlight apparatus includes a waveguide and a light source array, providing large area directed illumination from localized light sources. The waveguide may include a stepped structure, and the steps may further include extraction features optically hidden to guided light, propagating in a forward direction. Returning light propagating in a backward direction may be refracted, diffracted, or reflected by the features to provide discrete illumination beams exiting from the top surface of the waveguide. Viewing windows are formed through imaging individual light sources and define the relative positions of system elements and ray paths. The imaging directional backlight apparatus further includes a control system for controlling the light output directional distribution in an automotive or vehicle environment in dependence on the output from sensors mounted on the vehicle. The control system is arranged to control the light output direction distribution of portable directional displays co-located with the vehicle.
1. A display apparatus comprising:
a directional display device for use in a vehicle arranged to display an image, the directional display device having an angular output light distribution that is adjustable; and
a control system arranged to adjust the angular output light distribution of the directional display device on the basis of a received output signal from a vehicle sensor system provided on the vehicle, wherein the vehicle sensor system comprises a darkness sensor system arranged to detect dark ambient conditions, the control system being arranged to angularly restrict the angular output light distribution of the directional display device on the basis of the output of the darkness sensor system indicating that dark ambient conditions have been detected.
2. A display apparatus according to claim 1 , wherein the control system is arranged to angularly expand the angular output light distribution of the directional display device on the basis of the output of a gaze sensor system of the vehicle sensor system indicating that an occupant's gaze is directed at the directional display device.
3. A display apparatus according to claim 1 , wherein the control system is arranged to decrease the brightness of the directional display device and/or adapt the color balance of the directional display device for viewing in dark ambient conditions on the basis of the output of the darkness sensor system indicating that dark ambient conditions have been detected.
4. A display apparatus according to claim 1 , wherein the control system is arranged to restrict the angular output light distribution of the directional display device on the basis of the output of a brightness sensor system of the vehicle sensor system indicating that bright ambient conditions have been detected.
5. A display apparatus according to claim 4 , wherein the control system is arranged to increase the brightness of the directional display device and/or adapt the color balance of the directional display device for viewing in bright ambient conditions on the basis of the output of the darkness sensor system indicating that bright ambient conditions have been detected.
6. A display apparatus according to claim 1 , wherein the control system is arranged to expand the angular output light distribution of the directional display device on the basis of the output of a vehicle motion sensor system of the vehicle sensor system indicating that the vehicle is motionless for a specified time.
7. A display apparatus according to claim 1 , wherein the control system is arranged to direct the angular output light distribution of the directional display device towards an occupant on the basis of the output of an occupant sensor system of the vehicle sensor system.
8. A display apparatus according to claim 1 , wherein the display apparatus further comprises an orientation sensor arranged to detect the orientation of the directional display device and a control system arranged to vary the angular output light distribution of the directional display device on the basis of the output of the orientation sensor.
9. A display apparatus according to claim 8 , wherein the orientation sensor comprises an inertial sensor.
10. A display apparatus according to claim 8 , wherein the orientation sensor comprises a camera system and an analysis system arranged to detect the position of windows of the vehicle in images captured by the camera system.
11. A display apparatus according to claim 1 , wherein the directional display device is mounted to the vehicle.
12. A display apparatus according to claim 11 , wherein the directional display device is mounted to the central console of the vehicle.
13. A display apparatus according to claim 11 , wherein the directional display device is arranged to display an image captured by an image capture system facing rearwardly of the vehicle.
14. A display apparatus according to claim 1 , wherein the directional display apparatus is a portable apparatus, the control system of the directional display apparatus being arranged to communicate with a processing system of the vehicle.
15. A display apparatus according to claim 14 , wherein the processing system of the vehicle is arranged to communicate layout information to the control system of the directional display apparatus that identifies the internal layout of the vehicle, the control system is arranged to vary the angular output light distribution of the directional display device on the basis of the layout information.
16. A display apparatus according to claim 14 , wherein the communication with the processing system of the vehicle is by a wireless means.
17. A display apparatus according to claim 1 , wherein the control system is arranged to vary the angular output light distribution of the directional display device in a manner that reduces the incidence of light on windows of the vehicle.
18. A display apparatus according to claim 1 , wherein the control system is also arranged to vary at least one of the brightness, contrast, color balance or content of the image displayed on the directional display device.
19. A display apparatus according to claim 1 , wherein the directional display device comprises:
a directional backlight arranged to direct light into selectable viewing windows; and
a spatial light modulator arranged to modulate the light output by the directional backlight,
wherein the control system is arranged to vary the angular output light distribution of the directional display device by selecting the viewing windows into which light is directed.
20. A display apparatus according to claim 19 , wherein the directional backlight comprises:
an array of light sources; and
a directional waveguide arranged to direct light from each light source into a respective viewing window,
wherein the control system is arranged to vary the angular output light distribution of the directional display device by selecting which light sources are operated.
21. A display apparatus according to claim 20 , wherein the directional waveguide comprises:
first and second opposed guide surfaces for guiding input light from the light sources along the waveguide; and
a reflective end for reflecting input light back along the waveguide,
wherein the second guide surface is arranged to deflect light reflected from the reflective end through the first guide surface as output light.
22. A display apparatus according to claim 21 , wherein the first guide surface is arranged to guide light by total internal reflection and the second guide surface comprises a plurality of light extraction features oriented to direct light reflected by the reflected end in directions allowing exit through the first guide surface as the output light and intermediate regions between the light extraction features that are arranged to guide light along the waveguide.