Design of a bidirectional backlight using a pair of stacked light guide plates for large dual-view and 3D displays

This paper proposes a design of a bidirectional backlight using a pair of stacked light guide plates (LGPs) for large displays employed in time-multiplexing dual-view and 3D applications. The LGPs with superficial microconcavities can emit very concentrated light and prevent the light emitted by an LGP from being disturbed by another LGP. In order to demonstrate the feasibility of the design in large dual-view and 3D displays, the transverse width of the designed bidirectional backlight in the simulation was set 500 mm, equivalent to the size of a 23-in. monitor. Moreover, the design of two stacked wedged LGPs reduced its thickness to only 2 mm. According to the simulation results, the bidirectional backlight emits concentrated light in two directions from the upper and lower LGPs. Before an optical film was put on the backlight, the intensity peaks of the emitted light were at 71° and -76° with respect to the normal; angular distributions of the emitted light were 20° and 22.5°; uniformity was 84%; and optical efficiency was 87%. For dual-view application, an optical film with prisms of a 100° apex angle was designed to deflect the light emitted from the upper and lower LGPs into the directions at -40° and 40°, respectively; the cross talk was below 10%. For 3D application, an optical film with asymmetric multifaceted, inverted prisms was designed to concentrate the light emitted separately from the two LGPs and deflect the emitted light into the left and right eyes. The intensity peaks of the light emitted from the optical film were at 5° and -4° with respect to the normal; angular distributions of the light emitted from the optical film were 13° and 11°; and the cross talk for the left and right eyes was 5% and 7%, respectively.