3D Glasses Overview - Passive Polarized vs Active Shutter

If you have a 3D TV you need to use the right glasses

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

Although 3D viewing at home has fallen out of favor with TV makers and many consumers, there is still a small-but-loyal fan base, and there are still millions of sets in use around the world and the 3D viewing option is still available on many video projectors, and, there is still a flow of 3D movie titles available on Blu-ray Disc.

What all 3D TVs and video projectors have in common is that you need special glasses in order to view the 3D effect.

What 3D TVs and Glasses Do

3D TVs and 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 displays the left and right eye information on the TV or projection 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 receive the separate images and pass them properly to the left and right eye.

3D glasses work by providing a separate image to each eye. The brain combines the two overlapping images into a single image, which appears to be in 3D.

Types of 3D Glasses

  • 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 that 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: These glasses 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 syncs 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 jaggies artifacts on the edges of objects may be noticeable, mostly with text and straight line geometric shapes.

The 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 the brand or model TV/video projector you purchase will determine which type of 3D glasses are required.

When 3D TV was introduced, Mitsubishi, Panasonic, Samsung, and Sharp took the Active Shutter glasses route for 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 used mostly the Active system but offered some TVs that use Passive.

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 was up to the manufacturer.

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 provided glasses with the set or projector or offered them as an accessory that had to be purchased separately. Although production of 3D TVs has ended, 3D glasses are still available, but prices will vary. As mentioned previously, 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 that are branded for one brand of TV or video projector, 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, they will not be able to borrow each other's 3D glasses.

3D Without Glasses is Possible But Not Common

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

However, progress has been made as no-glasses 3D is becoming available on some smartphones, portable game devices, and there are a limited number of large screen TVs available for both consumers and commercial use from Stream TV networks and IZON technologies.