NEC WT600 White Paper

Nec wt600: reference guide

Hide thumbs Also See for WT600:

Download this manual See also: Command Manual, User Manual

NEC

White Paper

WT600 Used In Rear Projection Systems

The WT600 has a very short throw distance that makes it an attractive product to use in a rear projection (RP) system.

By using the WT600, the depth of the rear projection system can be reduced by half of a system using a traditional

projector. It is possible to design a system with a 100" diagonal screen that has a total depth of approximately 24"

(single mirror system).

The key to using the WT600 in a rear projection system is 'screen selection'.

The WT600 has a very steep projection angle (55°).

When the WT600 is installed on the opposite side of the screen from the viewer in an RP system, the image path

comes through the screen at a very steep angle. When the light path passes through the screen, the screen diffuses

much of the light so that the image can be seen from many angles. 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).

'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). This can cause a double image to occur. Secondary reflections can be

www.necvisualsystems.com

SOME LOST LIGHT

DIFFUSED

LIGHT

NEC Solutions (America), Inc.

Visual Systems

v1.0

Page 1 of 2

Page 1 WT600 Used In Rear Projection Systems The WT600 has a very short throw distance that makes it an attractive product to use in a rear projection (RP) system. By using the WT600, the depth of the rear projection system can be reduced by half of a system using a traditional projector.
Page 2 (not the viewer) to minimize the possibility of secondary reflection. Screens with a fresnel or ‘etched’ rear surface cannot be used since they require a projector with a zero degree offset lens. The WT600 does not have a lens, and as stated earlier, the image is projected at a very steep angle (55°).

Wt600wp rp white paper