Combining both high definition video and the capacity to show three-dimensional (3D) images, 3D high definition television (HDTV) is a new technology for watching movies and other video content. A 3D HDTV system uses a Blu-ray® or streaming media player to send a specially encoded signal to special HDTV sets that work with liquid crystal diode (LCD) shutter-based, active glasses or polarized "passive" glasses to actually display the signal. This technology can display remarkable images, but as of December of 2011, has received lukewarm response from the consuming public.
3D HDTV sets start out as regular HDTVs. They can display a 1,920 by 1,080 pixel image, also referred to as 1080p resolution, and typically have large flat screens. One distinguishing feature, which typically makes them excellent 2D sets, is that they must offer refresh rates of at least 120, but usually 240 hertz, leading to better reproduction of movement in both 2D and 3D images.
Active 3D HDTV sets have an additional feature that 2D sets lack. They have a special device that emits an infra-red signal to the active shutter glasses that viewers wear. These glasses quickly darken over each eye — usually 30 times per second — synchronized with the screen. The screen shows the image for the left eye, then switches to the right eye, and then back. Since the glasses prevent both eyes from seeing the screen at the same time, the viewer's brain fills in the blank areas and ends up seeing a 3D image.
Passive 3D sets work a little differently. These sets have a polarizing filter over the screen, where alternating lines emit light at a different polarizing angle. They display the image for the left line on one set of lines, and the image for the right eye on the other set of lines. Viewers wear polarizing glasses which block the right eye's image from reaching the left eye and vice versa.
3D HDTV images can be quite striking, appearing almost like a window onto the world. The technology has been only slowly adopted, likely due to the combined factors of limited content, high cost, and the requirement of wearing glasses. More than anything else, the glasses have proven to be a major source of consumer discontent. Active-shutter glasses tend to be expensive, heavy, and incompatible across manufacturers, making it impossible for people to bring their Brand X glasses to a friend's house to watch a Brand Y set. Although passive glasses solve these problems, that technology is relatively rare as of the end of 2011 and also carries with it a meaningful penalty in resolution.