1. CRT projection, this is a very old projector, after 2000, very few, mainly through three primary color CRT tube projection image, generally speaking, similar to the old big head TV, low brightness, low pixel, almost obsolete
2. LCD, LCD liquid crystal board is to penetrate projection, was the light of the light source through the LCD version, and then projected on a screen out the corresponding pictures, popular culture, like tiny time that a piece of the appearance of a slide projector, light through a translucent panels (LCD) and imaging without obscured parts, high saturation, brightness is lower, Screen comfort is its characteristic, now there are many such products.
3. Digital DLP projector, is also used when I design solutions, based on the DLP, Texas instruments processor screen after playing on the DMD reflected, so it is reflective projection, in layman's terms, DMD cmos similar to the SLR cameras, SLR cameras is just outside the light inside, the inside of the projector is light, light on the DMD, DMD is a collection of small mirrors on the nanoscale, and depending on where you control them, the mirrors turn at different angles, and one of the mirrors at the right Angle will reflect the light to the image, and the other will reflect the light elsewhere, and there will be no image, and then the pattern will come out. It's a very mature technology, high pixel, high brightness.