LAMPS, LEDS & LASERS
What we didn’t talk about in our general discussion of projectors was how their light is produced. Does it matter? Yes indeed.
Traditionally projectors have been powered by rather expensive incandescent lamps, usually called something like Ultra High Pressure. Life-time? Depending on the model, from around 2000 hours to 4000 hours, with a few stretching out in ‘Eco’ mode to as much as 8000 hours. But ‘Eco’ modes run at lower power, and thus at lower outputs — so they aren’t as bright. There’s a trade-o between lamp life and picture brightness. A replacement lamp typically costs at least a hundred dollars; some cost several hundred.
More recently other technologies have appeared. High powered LEDs have the advantage of a long life. Typically you’ll never replace the light source because the projector itself will be at the end of its service life aer the 20,000 hours or so for which the LEDs are rated. However that technology is being replaced by a new one: lasers.
No, these projectors don’t shoot lasers from their lenses. They fire a high powered laser inside their bodies at a clump of phosphor (it’s usually attached to a spinning disk), and that phosphor glows brightly. In eect, the system is turning one form of light — coherent light from a laser — into another form, with good eiciency.
These laser projectors also typically have a rated life of 20,000 hours (that’s four hours a day, every day for more than 13 years). But they have other virtues, such as more or less being instant on — or at least the lamp can switch on and o instantly, though the projector usually takes ten seconds to boot itself up before you get a picture.