Some interesting images of the new Sony Aplha range of DSLR cameras have been shown over at PC Mag. The images show how the new Live View features work and what actually goes on inside the camera to make it work.
The A500/550 will also feature an advanced version of "Live View" shooting , using your LCD as a viewfinder. Most cameras that offer "Live View" can't offer the fast phase-detection auto-focusing system that is in use when using the optical viewfinder. This is because "phase detection" auto-focus works by using a transparent mirror that reflects light from the lens downward and upward. Light goes downward to a small sensor that performs auto-focus, and the upward to provide the same image to the optical view finder so you can see what you're shooting.
The only time the camera uses the main sensor for showing Live View images is when it's in manual focus mode. When in auto-focus mode another sensor is used.
For full details on how it all works and how it speeds up the auto-focus on the cameras check out the article over at PC Mag.