Autostereoscopic display using a holographic splitter in polymer-dispersed-liquid crystals

In this paper, we develop a beam splitter based on a holographic optical element in polymer dispersed liquid crystals (PDLC) to generate a stereogram. As shown in Fig.1, to generate a stereogram on a liquid crystal panel, a beam splitter is essentially required to direct the image on odd pixels to propogate to right eye, and direct the image on even pixels to propogate to left eye of the observer. The comerical technic to generate the essential beam splitter is using a barrier or a lenticular array. The former method may reduce the brightness of the stereogram, and the latter technic may generate more cross talk noise. Instead of that, we propose a new technology for a beam splitter based holography. As shown in Fig.1, the whole beam splitter is a holographic optical element composited of many sub-holograms attached on each column pixels. The odd column pixels are marked with R and even column pixels are marked with L. The sub-holograms above the odd column pixels will diffract the images shown on R column pixels to propogate to right eye, and sub-holograms above the even column pixels will diffract the images shown on L column pixels to propogate to left eye. Fig.2 shows the experimental result of the holographic splitter. The image on R column pixels is a character “L” and the image on L column pixels is a character “V”. We can find these two images can be separated effectively. The diffraction efficiency for each image is about 40% in our experimental element, and accordingly the brightness of the stereogram is about 40% of the original brightness on panel. The brightness performance is much better than the barrier technology, which generate stereogram with low brightness only 23% of the original brightness on panel. The cross talk performance can be investigated by the contrast ratio (CR) of the diffracted images. The CR for right eye can be defined as: equation where R_r is the diffracted intensity of the image on R col- - umn pixels measured on location of the right eye, and R_l is the diffracted intensity of the image on L column pixels measured on location of the right eye. The CR_l for left eye can be measured by the similar principle. The contrast ratios for right eye and left eye of the holographic splitter are about 84%, respevtively. Our device shows larger contrast ratio for stereogram, and therefore, it generate less cross talk noise than lenticular technology.