Topic summary
LCD projection
Extracted from the Wikipedia article LCD projector.
History
At about the same time, the German company "Bonner Ingenieurbüro für Optoelektronik CrystalVision" started experimenting with LCD projection devices from 1985 onwards. Although traditional slide projectors already used infrared filters to reduce heating of the photographic slides, LCDs are much more sensitive to overheating. When the temperature in the nematic liquid crystal layer reaches the clearing point (i.e., enters the isotropic phase), the LC light valve does not work anymore until the temperature drops below again. Bernt Haastert, an engineer working at CrystalVision, found out, that placing the required polarizing filters at a certain distance on both sides of the LC cell allowed for efficient air cooling of the arrangement. Without applying this invention, LCD projectors with a powerful light source don't work. A commercial LCD projector based on this principle was launched in Germany in 1990 under the trade name "Imagina 90".