LIQUID CRYSTAL SWITCHED HOLOGRAPHIC DISPLAY
Original Publication Date: 1990-Apr-30
Included in the Prior Art Database: 2004-Apr-05
Xerox Disclosure Journal
Figure 1 illustrates a holographic liquid crystal display 2. A multiplexed hologram 4 is positioned on a substrate 5. A liquid crystal layer 6 is positioned between alignment layers 20 and 12 and is aligned by these layers so that its optical axis is parallel to the polarization of the incoming light beam. front and rear electrodes 14 and 16 are formed within the alignment layers. front (transparent) substrate 19 completes the display. A non-polarized light beam 18 is directed onto the display at an angle 8, = 30" to the display normal. It thus encounters the extraordinary refractive index of the liquid crystal, (say 1.7) and, by Snell's law, 82 = 26". The light beam will illuminate a first image in the hologram 4 at this angle. If a voltage is applied to the electrodes, the liquid crystal is reoriented so that the beam encounters the ordinary refractive index. This may be essentially the same as that of glass, say 1.5, and the beam is not refracted. Thus, the incident beam has been switched by 4" for a total change in the angle of incidence + reflection of 8". This change should be sufficient to allow the display to show a different image than before since the extend of the refraction is proportional to the sine of the angle of incidence 81.