Passive 3D glasses are any 3D glasses that don’t require a power source to view 3D content. The two major types of passive glasses are anaglyph and polarized 3D glasses. One of the main benefits to passive 3D glasses is cost. Since they do not require a power source or powered lenses, passive 3D glasses can be very inexpensive. Anaglyph glasses, commonly seen with one red and one cyan lens, are often seen made out of cardboard with cellophane lenses. Though anaglyph glasses do show the viewer a 3D image it is the least advanced of all methods of delivering 3D and because they use color to separate the images some or all color information is lost to the viewer.
Polarized 3D glasses come in two forms, linear polarized and circular polarized. Linear polarized glasses require the use to maintain a vertical head position, tilting your head left or right can break the 3D effect because the content relies on one eye seeing the vertically polarized image and the second eye seeing the horizontally polarized image. When the head is tilted the polarized lenses no longer line with the polarized double image on the screen. Circular polarization does away with this problem but it requires a special projector and filter and will not be used on 3D televisions.
Another benefit to passive 3D glasses is that since the viewer is being shown both images at once it does not half the frame rate of the content like active glasses do.
Advantages and disadvantages
With passive 3D, the viewer will see 540 lines of resolution to each eye, or half 1080p (provided the source is 1080p). So, theoretically the picture will have less depth and quality than one of 1080p. The advantages of passive 3D is that the glasses are much less expensive and need no power. 3D glasses of this variety can cost as little as $5 a pair and often come with the TV, so setting the family up for some 3D viewing will not hit the wallet as hard. Passive 3D viewing will not cause the eye strain and fatigue that active 3D will since the glasses are not actively opening and closing.
Recently, the debate between active and passive 3D is getting hotter due to the choices of manufacturers to produce one or the other technology. LG and Vizio are producing only passive 3D in their LED-LCD TV lineups. Panasonic, Samsung and Sony are producing active 3D only in their lineups. Toshiba is producing both active and passive 3D and also trying to bring to market the first 3D TVs without glasses. It will be interesting to see if the lower overall price point of passive 3D offerings forces the hand of the active 3D manufacturers.