What is the difference between active shutter glasses and passive polarized 3D glasses?
Active Shutter Glasses:
This technology has been adopted by most consumer electronics firms like LG, Samsung, Panasonic, etc. With this technology, an HDTV will display one image to your left eye and one image to your right eye. Since the effective frame rate is halved, these HDTVs need to have double the refresh rate of HDTVs (60 Hz). This is why you will find that all 3D HDTVs have a minimum frame rate of 120 Hz (most have a frame rate around 240 Hz or even 480 Hz). You will need a pair of active shutter glasses if you buy a 3D-capable HDTV in 2010 and onwards.
Passive (or Polarized) Glasses:
The display shows two overlapping images and the glasses have polarized lenses. Each lens is polarized so that it can see only one of the two overlapping images.
The only drawback is that viewers will need to sit directly in front of the display to get the full 3D effect. If the viewer is sitting on the side, the 3D effects will be less pronounced.