Display. Visualization — Projection and rear projection

Image projection systems have been around for several centuries now, and the basic principles have not changed fundamentally (figure 1 ). It has always been a matter of illuminating a small image with a light source and enlarging it with suitable optical elements.

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On the other hand, the technologies of the key components that make up the projector's backbone have greatly improved. Discharge lamps have replaced kerosene lamps, and the prints of past centuries have been successively replaced by photographic slides, cinema film and, more recently, electronic valves.

The only exception to this rule was the development of projectors using cathode ray tubes, where, in this particular case, the same component delivers both the information to be displayed and the light energy required to display it.

The aim of this dossier is to describe the various technologies involved in the world of electronic projection of moving images. The advantages and disadvantages of each solution will be discussed in relation to the two possible applications: front projection and rear projection.