Various thin screen technologies are being developed, but only the liquid crystal display (LCD),
plasma display (PDP) and Digital Light Processing (DLP) have been released on the public market.
These technologies have almost completely displaced cathode ray tubes (CRT) in television sales,
due to the necessary bulkiness of cathode ray tubes. However, recently released technologies like
organic light-emitting diode (OLED) and not-yet released technologies like surface-conduction
electron-emitter display (SED) or field emission display (FED) are making their way to replace
the first flat screen technologies in picture quality. The diagonal screen size of a CRT television
is limited to about 40 inches because of the size requirements of the cathode ray tube, which fires
three beams of electrons onto the screen, creating a viewable image. A larger screen size requires a
longer tube, making a CRT television with a large screen (50 to 80 inches) unrealistic because of size.
The aforementioned technologies can produce large-screen televisions that are much thinner.