Since 2008, Sony has been one of the main forces behind the 3D TV campaign. But so far many consumers have balked at the high price and the need to wear glasses.

Try as they might, Panasonic and Sony have yet to convince consumers that 3D TV is a necessity.

Released today, a new study commissioned by The NPD Group found that while people know more about 3D TV now, they're not generally any more convinced of why they need one.

A year and a half into the 3D TV era kicked off by Sony and Panasonic and since joined by others, 45 percent of people who said they wouldn't buy a 3D TV said the reason is it is too expensive. And 42 percent of people said the reason they wouldn't buy one is because they don't want to wear glasses. That's an increase in both categories--just six months earlier only 37 percent said price was the inhibiting factor in their purchase, and 32 percent said wearing glasses was. But interestingly, the increase of people who were hung up on 3D glasses was larger than people who thought the TVs were too expensive.

This NPD study follows a survey Nielsen conducted last fall that found, among other things, that 90 percent of respondents said they wouldn't want to wear glasses for 3D TV because it would hinder multitasking--like working on a laptop, or other things people generally do while sitting in front of the TV.

And therein lies the main problem with 3D TV. The prices of the sets will eventually fall--in fact it's already happening, more on that in a moment--but we're still not that close to not wearing 3D glasses while watching a 3D television at home. And unlike HDTV, which went from the new must-have feature to commodity item in less than half a decade, 3D TV still doesn't feel like it's anywhere near becoming as ubiquitous as HD despite the best efforts of TV makers.

"In the earliest days of HD, price was clearly the number once concern for people who might otherwise have an interest in the technology," Ross Rubin, NPD analyst who wrote the report, said in comparing the evolution of HDTV to 3D TV. "But in 3D we have this added wrinkle of the glasses."

The cost of buying a 3D TV for your own living room is lower than it's ever been--you can get can a 3D plasma TV for around $1,200 now. Sure, that's still twice what you can buy a regular plasma TV for, but it's a significant decrease from the $3,000 price tag of a year ago. Plus, there is a wider range of sizes available, and more manufacturers making them, which means they all start trying to beat each other on price, bringing down the price tag even further.

So what are manufacturers doing to combat the glasses issue While they can't make 42-inch 3D TVs work sans glasses just yet, there's a whole group of companies looking to make having to wear those pesky glasses less painful on your eyes and your wallet.

Samsung said starting later this month it will include two free pairs of lighter weight, rechargeable active-shutter glasses with its new 3D TVs. And instead of additional glasses being $130, they're now $50 a pop.

An example of the active-shutter 3D glasses those polled say inhibits them from buying a 3D TV.

There have also been attempts at making "universal" 3D glasses that can be bought once and used on TV at home and in the theater.

Trendy glasses maker Oakley is also trying to get a piece of the action. Last fall the company introduced a pair of 3D lenses that look like regular sunglasses, and work with passive polarized 3D TVs. That means you don't need to recharge them like battery-operated active-shutter 3D glasses. They're charging $120 for them, but Oakley also promises their optical experts built them so they won't strain your eyes.

However, these tweaks to 3D glasses technology are a short-term solution. The real endgame for all of this is auto-stereoscopic or glasses-free 3D TV.

Nintendo 3DS is the first real mainstream product that's an example of this. As a handheld gaming device, it's small. But it does produce a reasonable way of experiencing 3D without glasses for just $250. And some in the 3D industry see it as a sort of gateway for 3D outside of a movie theater.

Part of the reason people say they wouldn't want 3D glasses is that those people "are not seeing the value proposition of having 3D at home yet," argues Phil Lelyveld, manager of the Consumer 3D Experience Lab at USC's Entertainment Technology Center.

Most people have still not been exposed to 3D outside a movie theater and can't imagine what that would be like at home or why they need it, he says. "Which is why I see the 3DS as an important gateway to experiencing 3D in the home" for less than the cost of buying a TV set.

While glasses-free Nintendo may be a great place to start, it's a long way from an affordable glasses-free 3D TV most people would want in their living room.

Sharp&39's glasses-less 3D works well. But right now it only works at a size best suited to mobile devices, not TV sets.

TV makers are working on it though. Toshiba started selling a glasses-free TV in Japan in December, but it's at the rather unenticing size of 20 inches. The Japanese TV maker had told The Wall Street Journal in December that a 40-inch version would be ready by April, but Toshiba did not respond to a CNET request for comment on that. And there's no expected ship date for stores outside Japan.

Another TV maker, Sharp, is also working on glasses-free models, but like Toshiba's current offering, size is an issue. The 3.8-inch and 10.6-inch prototypes the company showed last fall worked rather well, but at the current size they're much better suited to mobile devices than a living room. The same can be said for LG, also working on smaller glasses-free 3D options for mobile devices.

There's a lot of research being done on the glasses-less 3D front. A good indication of how important this area of technology is going to be Apple is one of the companies researching it, as shown by the patent the company filed late last year. But it's still not ready for prime time. Or mainstream audiences.

"At the screen sizes that are prevalent in consumer living rooms today and in particular for 3D, where manufacturers have been pushing the 'bigger is better' agenda for enjoying the immersion effect, we seem to have some way to go," said NPD's Rubin. "It's probably a few years before we see affordable glasses-free 3D TVs competitive to what (3D with) glasses offer today."