LCD projector
LCD projectors are used for large screen presentations. Their use is recommended at training courses, congresses or other presentations in exhibition halls, airports and train stations. Like TFT displays, they work with liquid crystals which, when an electric field is applied, align their structure in a certain direction and thus control the flow of light.
For LCD projectors, there are two different technologies with one and with three TFT elements. In one-TFT panel technology, the LCD projector has one TFT element that is continuously illuminated by a projector lamp, and its light is distributed evenly and onto the LCD element via microlenses and color filters, without visible interference from the control lines of the thin-film transistors.
The TFT element consists of the individual layers with the liquid crystals, which are controlled by the signal source. In front of the LCD element is a projector lens for focusing the light beam.
The 3-TFT panel projector has three TFT elements for the three primary colorsred, green and blue. The light from the projector lamp is distributed evenly to all three TFT elements via dichroic filters. The color distribution of the monochromatic TFT elements is generated via color filters. The light is projected onto the projection surface via a downstream focusing device and the projector lens. This design corresponds to that of the HTPS projector(High Temperature Polysilicon), whereby the thin-film transistors are realized in high-temperature silicon technology.
The resolution of LCD projectors ranges from 100,000 pixels to 1.5 million pixels. The latter value may well apply to all three colors, i.e. it corresponds to an effective pixel count of 500,000. With this number of pixels, displays can be created in XGA and Super-XGA( SXGA) with 1,280 x 1,024 pixels. For video presentations, there are projectors for a format of 16:9 in addition to the aspect ratio of 4:3. The luminous intensities of LCD projectors range from 1,000 to 3,000 ANSI lumens.