High pressure mercury arc lamps are commonly used as the illumination source in many projection systems. Such lamps may be deficient in either output power or spectrum, and so it is desirable to combine the light from the lamp with light from a second light generator. The second light generator may be...http://www.google.de/patents/US7261423?utm_source=gb-gplus-sharePatent US7261423 - Combined light source for projection display
