User manual NEC WT600WP RP WHITE PAPER

[. . . ] NEC White Paper WT600 Used In Rear Projection Systems NEC Solutions (America), Inc. Visual Systems v1. 0 The WT600 has a very short throw distance that makes it an attractive product to use in a rear projection (RP) system. [. . . ] However some of the light keeps traveling at that steep angle after it passes through the screen and keeps traveling up so that some light may pass over the viewers' head when the projector is installed in desktop orientation. This portion of light is lost to the viewer (see diagram below). SOME LOST LIGHT DIFFUSED LIGHT 55° `Hot spotting' can also occur in areas on the screen, usually noticed at the very bottom of the screen in the middle, when the projector is installed in desktop orientation. This is also dependant on the height of the viewer's seating. In testing the WT600 in the environments described, we have found the location of hot spotting and the intensity is not very noticeable compared to a traditional projector with a rear lens where hot spotting tends to happen more around the center of the screen and usually at more intensity. Designers of RP Systems are also careful to use a screen and system designed to avoid the possibility of `secondary reflection'. Secondary reflection can occur when an RP system with mirrors is used. Often diffusion screens have a shiny side which when facing the projector can reflect some light back to the mirror which in turn will reflect back onto the screen a second time (see diagram). Secondary reflections can be www. necvisualsystems. com Page 1 of 2 avoided by mounting the screen with the diffusion side toward the projector and the shiny side toward the viewer. This look has much the same luster as a direct view TV. If a more matt surface is desired, screen manufacturers offer screens with AR (anti-glare) coatings on the viewer side. IMAGE HITS SCREEN TWICE MIRROR A screen that will give the best results should be a `diffusion type' and it should be installed so that the diffusion side is facing the projector (not the viewer) to minimize the possibility of secondary reflection. [. . . ] However the pros should far outweigh the cons for many users who need minimal depth in an RP system. It is also very important that the integrator work with a screen manufacturer who has the expertise in designing an RP system that will give optimum performance when a WT600 is used within the system. www. necvisualsystems. com Page 2 of 2 [. . . ]