Directional backlight

3 M has demonstrated a autostereoscopic 3-D display based on a directional backlight unit [48-50]. 

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Figure 16.17 Working principle of an autostereoscopic display with a directional backlight unit. Reproduced with permission from Wiley.

T. Sasagawa, A. Yuuki, S. Tahata, et al., Dual directional backlight for stereoscopic LCD, SID Tech. Digest 34, 399 (2003). 

R. Brott and J. Schultz, Directional backlight lightguide considerations for full resolution autostereoscopic 3D displays, SID Tech. Digest 41, 218 (2010). 

In order to summarize this section it must be noted that the possibility to evaporate conjugated oligomers in such a way that their chain axes point predominantly in one direction allows us to determine the anisotropic electronic properties of conjugated molecules. From these studies it becomes evident that in order to obtain polarized absorption or emission of light as required in polarization Filters or LCD-backlights, the application of conjugated molecules is one of the most attractive areas of application for these materials. 

In backlight or shadowgraph technique, the light comes from behind and is directed toward the camera. This technique is very useful in measuring bubble or drop size distributions (Figure 15.3). 

At Siemens the effort is directed to develop devices for use in backlighting for the keys on mobile telephones or for the liquid crystal display devices. Polymers displays... 

In order to show how these lamps are used, it is necessary to describe liquid crystal displays (LCD). We will not describe this technology thoroughly since it does not directly relate to the use of phosphors in the display, except in the fluorescent lamps used for "backlighting" the LCD. A "liquid crystal"- (LC) is an organic compound whose molecules align themselves with an applied electric field. An LC substance flows as a liquid but maintains some of the ordered structure characteristic of a crystal. 

Similarly, the reflective LCDs can be subdivided into direct-view and projection displays. In principle, a direct-view reflective LCD does not require a backlight so that it is light in weight and its power consumption is low. A major drawback is poor readability under weak ambient light. Thus, a reflective LCD is more suitable for projection TVs employing liquid-crystal-on-silicon (LCoS) microdisplay panels. In an LCoS, the reflector employed is an aluminum metallic mirror. The viewing angle is less critical in projection displays than in direct-view displays. 

Investment in Japan resulted in the start-up of a second PC production line dedicated to the manufacture of sheet to be used in diffusion plates or large screen LCD-TV direct-type backlights. PC sheets have higher heat resistance than the PMMA and methacrylic material formerly used. 

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