Notion of light output

The luminous efficacy of the electro-optical modulator- or valve-based projectors we've just studied (LCD, LCOS, DMD) is reasonably low, on the order of 5% for a consumer rear-projection application, for example. In this section, we explain the reasons for this situation, as well as the fundamental limitations set by the principle of the geometric extent of a light beam (see box).

Regardless of the technologies used, which have been described above, a valve-based projector consists of four more or less distinct parts:

• the lighting system (§ 5.1 ...