ABSTRACT
Projection usually means the formation of a bright image on a suitable screen. The subject is usually planar, or only slightly curved as in the case of a video display unit screen. Projection arrangements of imaging plus illumination systems are designed for specific image formats in photography, cinematography, audiovisual and video work. The geometry of projection is such that the image is seen correctly orientated in the screen. The projection lens is usually simple in design and incorporates a mirror to reflect the image for correct orientation. Images viewed by rear projection on to a translucent screen, also called back-projection, can solve viewing problems of high ambient light and small or low-ceilinged rooms where front-projection is unsuitable. When the projector is designed as a permanent installation in a purpose-built lecture theatre, more complex projection optics and high-power sources may be used to give a very large screen image.
