Patent ID: 9678267
Date: 2017-06-13
CPC Classifications: G02B,G09G,H04N

Claim:
1. A directional backlight apparatus comprising: a waveguide extending between an input end for receiving input light and a reflective end for reflecting the input light back through the waveguide; an array of light sources disposed at different input positions in a lateral direction across the same input end of the waveguide, the waveguide having first and second, opposed guide surfaces extending between the input end and the reflective end for guiding light forwards and back along the waveguide, the waveguide being arranged to reflect input light from light sources at the different input positions across the input end after reflection from the reflective end into respective optical windows in output directions distributed in the lateral direction in dependence on the input positions; a control system arranged to selectively operate the light sources to direct light into selectable viewing windows at different locations and comprising at least one of the optical windows; and a sensor system configured to detect a position of an observer, wherein the reflective end converges the reflected light such that reflected light from light sources that are offset from the optical axis of the waveguide fails to illuminate outer portions of the waveguide, the waveguide further comprises sides, extending between the input end and the reflective end and between the guiding surfaces, that are planar surfaces arranged to reflect light from the light sources, the control system being arranged, on selective operation of a first light source to direct light into a first of the viewing windows, to simultaneously operate a second light source that directs light into the first of the viewing windows, wherein the light of the second light source is reflected by the reflective end and then by a side of the waveguide into the outer portion of the waveguide that fails to be illuminated by the first light source, and the control system is configured to control a spatial light modulator to display temporally multiplexed left and right eye images and synchronously to operate the light sources to direct light into at least one viewing window in positions corresponding to the left and right eyes of the observer, in dependence on the detected position of the observer.