How do 3D active shutter glasses work?

Active shutter glasses utilize liquid crystal lenses that alternately 'block' one eye and then the other in sync with your 3D HDTV (via infrared or Bluetooth® signal), which alternates left and right eye High Definition images on the screen at a very high rate. This image alternation and blocking mechanism is fast enough that the brain takes the two different views from both eyes, and merges them together into one image with depth. Most active shutter glasses run on batteries; select models are rechargeable.