A visual display unit (VDU) based on projection technology is composed of a projector and a projection screen. These are either custom built by a systems integrator or based on standard display units from a display provider. The characteristics of the screen and projector jointly determine the overall performance of the VDU. The screen and projector need to be matched to meet the ergonomic demands (brightness and contrast in relation to background and ambient illumination). Adequate contrast ratios can be achieved only by using controlled lighting and projection screens that absorb a part of the ambient light. If this is not done, ergonomics is sacrificed and crucial detailed information might be lost by the operator looking at the VDU.
The basic advantage of a projection system is that the image size is scaleable. This means that the VDU can easily be optimised to the actual need when designing the installation. However, the brightness and resolution of the projector might determine a certain limitation. Projection systems are often tiled in order to ‘multiply’ the performance of each individual projector into a larger display.
There exist basically two different projection philosophies: front projection, where the projector is placed in front of the projection screen, and rear projection, where the projector is placed behind the screen.