Early experiments with liquid crystals to generate a video image were done by John A. van Raalte at the
RCA-Laboratories in 1968. His concept was based on e-beam-addressing to generate an electronic charge pattern corresponding to a video image, which in turn controlled the LC layer of a reflective LC cell. E-beam-addressing requires a
CRT with a modified faceplate to generate a charge pattern on its surface. No practical application of this concept for projection purposes is known. However, a similar concept was used for
print heads without an LCD. The first experiments with a direct-driven, transmissive matrix-addressed LCD using a converted slide projector by
Peter J. Wild working at
Brown Boveri Research in
Switzerland were conducted in 1971. A projector was shown in operation at the SID Conference 1972 in
San Francisco. As direct-driven, passive LCDs (without
thin-film transistors) at the matrix intersections) were not capable of displaying images with sufficient resolution for video pictures, a combination of a fixed image together with an LCD matrix for the variable elements was proposed as an LC projector for certain control room applications, with a corresponding patent filed in Switzerland on Dec. 3, 1971. A lot of effort went into optimizing thin-film transistors (TFT) suitable for
active matrix-addressed (AM) LCDs. The concept was invented and early trials were conducted by teams at
RCA and
Westinghouse Electric.
T Peter Brody left Westinghouse and founded Panelvision in 1981 to manufacture AM LCDs. Breakthroughs occurred elsewhere in new materials and thin-film structures, with
Hitachi of Japan as a pioneering company. Such AM LCDs became commercially available in the early 1980s. Gene Dolgoff had the idea of using LCDs as light valves in projectors. However, he had to wait until 1984 to get a digitally-addressable LCD matrix device with sufficient resolution and contrast, which is when he completed building his LCD video projector. After building it, he saw many problems that had to be corrected including major light losses and very noticeable pixels (sometimes referred to as the "
screen-door effect"). He then invented new optical methods to create efficient and bright projectors and invented de
pixelization to reduce the screen-door effect. 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". With patents filed worldwide (filing his first LCD video projector patent application in 1987), Dolgoff started Projectavision, Inc. in 1988, as one of the world's first dedicated LCD-projector companies, which he took public on
Nasdaq in 1990. He licensed the technology to other companies including
Panasonic and
Samsung. Early pioneers of LCD projection in Japan were Epson and Sharp, which launched their own color video projector products in 1989. In 1989, Projectavision, Inc. was awarded the first
Defense Advanced Research Projects Agency (DARPA) contractfor
US$1 millionfor proposing that the United States
high-definition television (HDTV) standard should use digital processing and projection. As a member of the
National Association of Photographic Manufacturers Standards Subcommittee, IT7-3, Dolgoff along with Leon Shapiro, co-developed the worldwide ANSI standard for measurement of brightness, contrast, and resolution of electronic projectors. Since 2005, the only remaining manufacturers of the LCDs for LCD projectors are Japanese imaging companies
Epson and
Sony. Epson owns the technology and has branded it as "
3LCD". To market 3LCD projector technology, Epson also set up a consortium called the "3LCD Group" in 2005 with other projector manufacturer licensees of 3LCD technology that use it in their projector models. Early LCD systems were used with existing overhead projectors. The LCD system did not have a light source of its own: it was built on a large "plate" that sat on top of the projector in place of transparencies. This provided a stop-gap solution in the era when the computer was not yet a universal display medium, creating a market for LCD projectors before their current main use became popular. This technology was employed in some sizes of
rear-projection television consoles when there was a cost advantages in mid-size sets (40- to 50-inch diagonal). In 2014, 60-inch 1080p flat panel televisions were less costly than a projector with 1080p native resolution. Projection systems were typically marketed as offering a diagonal image size of 100 to 300 inches. In 2004 and 2005, LCD front projection began a comeback with the introduction of the dynamic iris and other modifications that have improved perceived contrast to levels similar to DLP. The basic design of an LCD projector is frequently used by hobbyists who build their own DIY (
do-it-yourself) projection systems. The basic technique is to combine a high
color-rendering index (CRI)
high-intensity discharge lamp (HID lamp) and
ballast with a condenser and collector
Fresnel lens, a single color LCD removed from a common computer display or electronic device and a
triplet lens. This design can also be used in low cost (around US$200) LCD projectors. ==See also==