Directional BLUs for Full Resolution Field Alternative Auto-stereoscopic 3D/2D and 2D/3D LCDs

Switching-directional backlight units (BLUs) were designed and prototyped for full resolution field alternate auto-stereoscopic 3D liquid crystal displays (LCDs). Since the design concepts are different for 2D/3D and 3D/2D displays, 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. A design based on the 2D concept required a uniform bilateral prismatic structure with a cross-section of isosceles triangle on the back surface of the functional light-guide plate (LGP). This structure led to an increase in double-sided uniformity, i.e., for double-sided illuminations (2D as primary function of the 2D/3D display), and a decrease in single-sided uniformity, i.e. for single-sided illumination. However, a design that was based on the 3D concept required an angle gradation for the unilateral prisms with a cross-section of a scalene triangle on the back surface of the functional LGP that led to an increase in single-sided uniformity and a decrease in double-sided uniformity (3D as primary function of the 3D/2D display). Both switching concepts were used to display 3D and 2D on the LCDs of small size handheld game devices and still cameras.