What is the difference between active and passive glasses?

Active glasses are made of LCD shutter lenses that run on battery(s). The 3D video footage is presented at 120 times per second, a left image and a right image flickers on the screen. In perfect coordination with this, the lenses in the active shutter LCD glasses turn from opaque to transparent. To capture the 3D experience, when the left image in the 3D video is displayed on the screen, the left lens is transparent. As the screen changes to the right image, the left lens turns opaque and the right lens changes to transparent. These changes in the eyeglass lens flicker at a speed of 120 times per second, thus creating the viewable 3D image.

Passive glasses are made of polarizing lenses that is very similar to those often used in movie theaters and amusement park rides. Each image is polarized to match one passive eyeglass lens and each image is then shown to each eye at the same time. Passive glasses feature different polarizing filters that filter the projected images to both the left eye and the right eye simultaneously. The passive glasses don't require a power source or batteries to view a 3D content.