The key is the screen's resolution (pixel count). Actually, there has been development of small screens (1"-3") that can contain far more pixels than previous versions - basically new technology. I can't remember the actual pixel count off hand, but this technology allows for tremendous detail to be viewed even in a small screen.
Keep in mind as the closer you get to a screen, the larger the viewing area. A 2" screen is comparable to a 42" plasma if your eyes are close enough. If you have enough pixels (or comparable technology), it will look just as detailed.
Jasman