By Alfred Poor, dealnews contributor Today, you have two main choices when buying a new HDTV with stereoscopic 3D support: shutter glasses or passive retarder technology. Both approaches are designed to deliver different images to your left and right eyes, which your brain then combines to create the illusion of a three-dimensional image. But a third choice may be on the horizon. Which solution will win out for your 3D TV purchasing dollars? Here's how the battle lines are being drawn: Shutter Glasses The most common available kind of 3D glasses on the market now are shutter glasses, also known as "active glasses." These were first available for some rear-projection HDTVs from Panasonic and Samsung, among others. Mitsubishi still makes DLP models with this feature. [Model WD-65638 available from Walmart for $899 is one example.] The system is also used on most of the plasma and LCD flat panel HDTVs with 3D support, with models from Sony, Samsung and Panasonic. One problem with shutter glasses is that they can be clunky and expensive, priced at $150 to $200 each. This situation is improving now that Samsung recently cut the price of a pair of shutter glasses to just $50 (which is less than the cost of a quality pair of good sunglasses these days). The glasses still need power, which means recharging or changing the batteries. Passive Retarder The passive retarder approach polarizes the light from the display in two different directions, alternating direction from one line of the pixels to the next. LG has championed this approach, and builds the panels this way for their own 3DTVs [Model 55LW5600 available from Crutchfield for $2,400 is one example] as well as for Vizio's new models that use the passive retarder technology. [Model XVT3D650SV available from Dell for $3,500 is an example.] The advantage of this approach is that you can wear inexpensive passive glasses that look basically like sunglasses (but are not exactly the same as the glasses you get for 3D movies in theaters). [Model AG-F200 available from Vann's for $22 is an example.] They don't need to be recharged, obviously, but they work because have special polarization in each lens that blocks the image intended for the other eye, and only transmits the image intended for that eye. One problem with this technology is that only half of the resolution of the screen reaches each eye. This is no problem for 3D content that has been encoded as "over/under" where each image is delivered in half resolution, compressed vertically. Some content is encoded "side by side," however, which means that the left and right images are compressed horizontally. In this case, you only get one quarter of the full 1080p resolution. It's not clear how much of a problem this reduced resolution will be for consumers. Keep in mind that the majority of HDTV owners watch standard definition DVDs on their sets all the time, and many think that they're watching high definition images. A Third Way The best of both worlds might be to have a television that delivers the full resolution to each eye, but still lets you wear inexpensive and lightweight passive glasses, just like you can in your local cinema. It appears that you may get that choice before long. At the Society for Information Display conference last week in Los Angeles, I saw a technology demonstration that's the result of a partnership between Samsung and RealD. Samsung is one of the world leaders in LCD panel technology, and while not as famous, you may also recognize RealD's name because it's one of the most popular technologies for stereoscopic 3D cinema in this country. Together, they came up with a way to switch the polarization of the image from an LCD HDTV, and do it fast enough that you see a 3D image. The trick is to put a second LCD panel in front of the main one. This has no color filters, and simply switches the polarization from one direction to the other. The end result is a 3D-capable HDTV that you can watch using the same passive glasses that you'd use for a RealD cinema screening. This may seem at first to be an expensive add-on, and you're probably right. On the other hand, the price of LCD TV panels is still falling and this would be a lot simpler solution than what's being used now. The patterned retarder approach also requires an additional layer; while it probably costs less than a second LCD panel, it also requires more precise positioning which could boost the manufacturing costs. At this point, Samsung has not made any announcement about pricing or ship dates for a commercial product. I suspect that it will proceed with the project, as the display looked great to me. It offers many of the best features of shutter glasses and passive retarder technologies, and if the price premium is not too great, it should be an attractive third choice. Photo Credit: Alfred Poor. About the photo: This 46-inch 3D-capable LCD HDTV was created jointly by Samsung and RealD, and displayed at the Society for Information Display conference, Display Week 2011, in Los Angeles. The screen uses a novel technology to rapidly alternate the polarization of the image so that you can wear inexpensive passive glasses and still see a full-resolution high-definition image in stereoscopic 3D. Alfred Poor, known on the Web as the HDTV Professor, is an independent technology industry analyst and freelance writer based in Pennsylvania, specializing in PC-compatible microcomputer hardware and software products. He was a contributing editor to PC Magazine and Computer Shopper, and currently is a columnist at HDTV Magazine.