17-09-2009, 01:25 AM
Digital Light Processing
Large-screen, high-brightness electronic projection displays serve four broad areas of application:
(1) electronic presentations (e.g., business, education, advertising),
(2) entertainment (e.g., home theater, sports bars, theme parks, electronic cinema),
(3) status and information (e.g., military, utilities, transportation, public, sports) and (
4) simulation (e.g., training, games).
The electronic presentation market is being driven by the pervasiveness of software that has put sophisticated presentation techniques (including multimedia) into the hands of the average PC user.A survey of high-brightness (>1000 lumens) electronic projection displays for comparing the already existing three types of projection display technologies namely, Oil film, CRT-LCD, and AM-LCD was conducted. Developed in the early 1940s at the Swiss Federal Institute of Technology and later at Gretag AG, oil film projectors (including the GE Talaria) have been the workhorse for applications that require projection displays of the highest brightness. But the oil film projector has a number of limitations including size, weight, power, setup time, stability, and maintenance. In response to these limitations, LCD-based technologies have challenged the oil film projector. These LCD-based projectors are of two general types: (1) CRT-addressed LCD light valves and (2) active-matrix (AM) LCD panels. LCD-based projectors have not provided the perfect solution for the entire range of high-brightness applications. CRT-addressed LCD light valves have setup time and stability limitations. Most active-matrix LCDs used for high-bright-ness applications are transmissive and, because of this, heat generated by light absorption cannot be dissipated with a heat sink attached to the substrate. This limitation is mitigated by the use of large-area LCD panels with forced-air cooling. However, it may still be difficult to implement effective cooling at the highest brightness levels.
