3D Glasses Overview - Passive Polarized vs Active Shutter

3D Glasses Example (Active Shutter Type)
3D Glasses Example (Active Shutter Type). Robert Silva

What 3D Glasses Do

3D glasses work by providing a separate image to each eye. The brain then combines the two images into a single image with 3D characteristics. The 3D process fools your brain into thinking it is seeing a 3D image, so it creates one for you.

3D-enabled TVs and 3D-enabled Video Projectors work by accepting an incoming 3D signal that is encoded by the content provider, which can be sent in several different ways.

The TV or projector has an internal decoder that can translate the type of 3D encoding used and and displays the the left and right eye information on the TV screen in such a way that it appears to look like two overlapping images that look slightly out of focus.

One image is intended to be seen only by the left eye, while the other image is intended to only be seen by the right eye. In order to view this image properly, the viewer must wear glasses that are specially designed to send the left and right eye images properly to the left and right eye. When viewing the overlapping images through these special glasses, the image appears to be in 3D.

Types of 3D Glasses

Glasses used for viewing images displayed on a 3D TV or 3D video projector with screen are of two types:

One type is referred to as Passive Polarized glasses. These glasses look and wear much like sunglasses and require no additional power to work.

They usually have enough front space to place over existing eyeglasses for those than need to. These type of glasses are inexpensive to manufacture and can range in price from $5 to $25 for each pair depending on the frame style (rigid vs flexible, plastic vs metal).

Active Shutter glasses, which are slightly bulkier than passive glasses, since they have batteries (some use watch batteries, others provide rechargeable batteries), on/off button, and a transmitter that synchs the rapidly moving shutters for each eye with the onscreen display rate.

These type of glasses are also more expensive than passive polarized glasses, ranging in price from $75 to $150 depending on the manufacturer.

Advantages of Passive Polarized 3D Glasses:

  • Lightweight
  • Inexpensive - About one third, to one quarter the price of Active Shutter glasses.
  • No flickering - which means less discomfort and eye fatigue over long view periods.

Disadvantage of Passive Polarized 3D Glasses

  • The 3D image that is viewed is one-half the resolution of a 2D image displayed on the same television (although proponents of passive glasses dispute this). This is because both left and right eye images are displayed on the screen at the same time. Check out the two sides of this issue represented by Joe Kane and Dr Raymond Soneira.
  • The presence of horizontal lines on the screen and some jaggie artifacts on the edges of objects can be noticeable, most notably with text and straight line geometric shapes.

Advantage of Active Shutter 3D Glasses:

  • The 3D image resolution is the same as the 2D image displayed on the same television. This is because the left and right eye images are displayed in a sequential fashion, in synch with TV or projector's screen refresh rate and the opening and closing of the LCD shutters in the glasses.

    Disadvantages of Active Shutter 3D Glasses:

    • Flickering due to rapid opening and closing of the LCD shutters may be detectable by some viewers, causing discomfort.
    • Heavier and Bulkier than Passive Glasses
    • Battery power required.
    • Expensive - Two or three times the price of Passive Polarized Glasses.

    The Glasses Have to Match the TV or Video Projector

    Depending on which brand and model TV or video projector you purchase, determines on what type of 3D glasses are required.

    When 3D TV was introduced, manufacturers, such as Mitsubishi, Panasonic, Samsung, and Sharp took the Active Shutter glasses route to their 3D TV products, at least with regards to LCD, Plasma, and DLP televisions (both Plasma and DLP TVs have been discontinued), while LG and Vizio promoted Passive Glasses for 3D LCD TVs, and Toshiba, and Vizio although mostly using passive glasses, some their LCD TVs did use Active Shutter Glasses.

    To make things even more confusing, Sony uses mostly the Active system, but offers some TVs that use Passive.

    One interesting thing to note is that due to the technology used to display images on Plasma TVs, only Active Shutter glasses can be used. However, both Active Shutter and Passive Glasses can be used with LCD and OLED TVs - the choice is up the manufacturer as to which they want to offer consumers.

    It is also important to note that consumer based 3D-enabled video projectors require the use of Active Shutter 3D glasses. This allows the projector to be used with any type of screen or flat white wall.

    Some manufacturers may provide glasses with the set or projector, or they may be an accessory that must be purchased separately. Manufacturers that do provide glasses with their sets normally provide one or two pairs, with the option of purchasing additional pairs as desired. Prices for the glasses will vary, at both the manufacturer's discretion and what type they are. As mentioned above, active shutter glasses will be more expensive (probably $75-$150 a pair) than passive polarized glasses ($5-$25 a pair).

    Also, another factor to take into consideration is that glasses branded for one manufacturer may not work another's 3D-TV or video projector. In other words, if you have a Samsung 3D-TV, your Samsung 3D glasses will not work with Panasonic's 3D-TVs. So, if you and your neighbors have different brand 3D-TVs, you will, in most cases, not be able to borrow each other's 3D glasses. For more details on why 3D Glasses for one brand 3D-TV may not work with another 3D-TV, check out the report from Big Picture and Sound.

    3D Without Glasses is Possible But Not Very Available...For Now

    There are technologies that enable viewing of 3D images on a TV (but not video projectors) without glasses. Such special application units exist, usually referred to as "AutoStereoscopic Displays". Currently, these displays are extremely expensive and, in most cases, you have to stand or site right in center or at very narrow angle from the center, so they are not good for group viewing.

    However, progress is being made as no-glasses 3D is becoming available on some cellphones, portable game devices, and is slowly becoming available for consumers in large screen TV form via Stream TV networks andIZON technologies.

    For more details on the sets offered by Stream TV Networks and IZON, as well as additional information on the current state of no-glasses 3D viewing, refer to my article Can I Watch 3D Without Glasses?

    For an in-depth look at what else you need to know about 3D, check out my Complete Guide to Watching 3D at Home.