Enhancement of viewing angle with homogenized brightness for autostereoscopic display with lens-based directional backlight

We have been developing an autostereoscopic display with directional backlight using Fresnel lens array. The system was originally composed of a dot matrix light source and a convex lens array and a LCD panel. We have previously proposed the methods to achieve uniform brightness and to expand the viewing zone free from crosstalk. The way to achieve uniform brightness is to add a vertical diffuser between the convex lens array and the LCD panel. The way to expand the viewing zone free from the crosstalk is to attach a large aperture convex lens onto the surface of the convex lens array. However, there still is a drawback that the viewing angle with homogenized brightness is narrow due to the darker peripheral part of the display region than the central part. In this paper two methods to enhance the viewing angle with homogenized brightness are proposed. The first one is to place two mirror boards on the upper end and the lower end between the convex lens array and the LCD panel horizontally. The second one is to place the large aperture convex lens just behind the LCD panel. By the first method, it is expected to reflect the directional light vertically and to make the upper and the lower part of the display region brighter, which enhances the viewing angle vertically. By the second method, it is expected that the directional light from the light source can be utilized more efficiently, which enhances the viewing angle horizontally and vertically.