Switching directional BLUs for full-resolution auto-stereoscopic 3D/2D and 2D/3D LCDs

Directional backlight unit (BLU) design concept was applied to realize full-resolution field alternate auto-stereoscopic liquid crystal displays (LCDs) with built-in 3D/2D and 2D/3D. The application-oriented BLU design requires priority in realizing 2D mode or 3D mode. The switching characteristic of BLU with two confronting illuminating sets was applied to build 2D mode into 3D display and 3D mode into 2D display. An LCD with 2D mode as primary function requires higher double-sided luminance uniformity than 3D mode. On the other hand, an LCD with 3D mode requires higher single-sided luminance uniformity than 2D mode. For increasing the double-sided luminance uniformity for 2D mode as a primary function of the display, the former BLU design was realized by using uniform prismatic structure, that is, using uniform bilateral prismatic structure with a cross section of isosceles triangle on the back surface of the light-guide plate. For increasing single-sided luminance uniformity for 3D mode as a primary function of the display, the latter was realized by using graded angle design, that is, unilateral prisms with a cross section of a scalene triangle on the back surface of the light-guide plate. The LCDs of small-sized-handheld game devices and still cameras were fabricated using the 3D/2D and 2D/3D displays.