Wireless, Anyone?

The most common question I get asked when demonstrating the Sensics head-mounted displays is "Can you make them wireless?" Just like the transition from a corded phone to a cordless phone and then to a mobile phone, there are numerous reasons to wish that HMDs could be untethered: no more having to carry an 'umbilical cord' cable around, or worry about tripping over it; fewer distance limitations; greater freedom of movement.

The day of 'cutting the cord' is now here. During the first week of December, my company will demonstrate a wireless HMD at the I/ITSEC show in Orlando, and I can't wait to see the responses.

Imagine a virtual reality application to train NFL quarterbacks, who already wear helmets for a living. Let's attach a high-performance HMD to the helmet and let the quarterback move around while seeing next week's opposing defense. Maybe even add an eye tracker to make sure he is scanning the field correctly and looking at the right passing options. With tethered HMDs, this application is a problem: quarterbacks are so expensive these days, that teams might be concerned about having them trip over a cable or get tangled up. With a wireless HMD, many additional options are open.

The same is true for numerous other applications: driving simulators, maintenance trainers, infantry trainers, just to name a few.

What makes wireless video for virtual reality applications more difficult is the concern about latency and frame rate. If you are watching a movie on a TV at home, and that TV receives a wireless video signal from your PC, there is no problem if there is a consistent delay between transmit and receive. Who cares of the movie is 2 seconds delayed? But if you are wearing an HMD with a motion tracker, and the image changes based on your movements, you are on a strict latency budget. Too much latency, and you are likely to experience motion sickness. The same goes for frame rate, where interactive applications need high refresh rate.

Wireless, anyone? Come to Orlando.

Weight watchers

How much can an HMD weigh before using it becomes a long-term wellness risk? 1 lb? 2lbs? 3lbs? Is a 2 lb (1 Kg) HMD that has a front-loaded weight concentration better or worse than a 3 lb model that has a counterweight on the back to balance it? Should users be more concerned about neck strain from trying to balance an HMD or about neck compression from wearing a large weight on their head for more than a minute or two?

Clearly, the answer also depends on the expected usage scenario. If the HMD is to be used in a static position such as near a desk, a 'boom' arrangement might be just fine. Alternatively, if rapid movement or usage that is longer than 10 minutes is expected, the answer might be different.

When My company designed the panoramic, high-definition xSight (12 oz, about 300 grams), we decided to conduct our own experiments to determine what acceptable weight would be. The head-mounted portion of the xSight was modeled after a ski goggle and for the experiments we would wear ski goggles with fishing weight taped to their sides. We would sit through meetings and other parts of the work days wearing the ski goggles with fishing weights. It was clearly evident for each of us how much weight is acceptable and how much is not.

One concern when potential customers look at an HMD is that they use it for a minute or two at the trade show. Under these situations, even a 3 lb HMD might seem acceptable, though if the user would wear it for 10 minutes, weight would become a very big issue.

So - watch the weight of your HMD.

HMD Knowledge in a Bottle

We took the time to capture some of HMD knowledge in a fairly extensive document which can be obtained here. It summarizes hundreds of customer discussions regarding important attributes in professional HMDs, (NOT old-fashioned HMDs like the one in the picture) and many of the little things that make a big difference to HMD users, some of which you might not find on product spec sheets. In a way, we captured 'HMD knowledge in a bottle'. I'd love to hear back comments on where this white paper is wrong or right, and what else is missing.

Movie Night

In my virtual reality company, we demo our product to many people. It seems that everyone has their favorite movie including a head-mounted display. Some of the common ones we hear are:

• Disclosure
• The Lawnmower Man
• Star Trek (as in 'can you create a Holodeck?')
• Demolition Man (though no one remembers the name of the movie, only Stallone's HMD scene)
• Vanilla Sky

and an honorable mention to Forbidden Science, a late-night series that used one of our products as a prop.

The Year of the Lightweight HMD

I think it's time that the weight of professional HMDs (those with high resolution and wide field of view) gets measured in ounces (or grams) and not in pounds (or kilograms), and I think this will happen in  2009.

Weight is so important in HMDs that it is sometimes overlooked. Lower weight means greater comfort. It means the ability to wear the HMD for longer amounts of time. It means that you can almost forget you are wearing it. Balance (as opposed to front-heavy) is also important as it impacts neck strain. Sometimes, HMD vendors add a counter weight in the back to balance their front-heavy design, but that's clearly the wrong solution.

Why do professional HMDs have to be heavy? The traditional thinking is that this is like asking why a manned fighter jet has to be heavier than an unmanned plane (e.g. drone or UAV). The pilot and flight suit add about 100 Kg to the jet, but that's just the beginning. Now you need oxygen, and a seat that you can eject, and instrumentation you can read. Before you know it, you need larger engines to carry this weight and longer wings and more fuel, so the net difference is much larger than the weight of the pilot.

Traditionally, that has been the thought of professional HMD vendors. The idea was that if you want wider field of view, you need a large lens, and to minimize distortion it needs to be complex and heavy. If you needed high resolution, you had to use more expensive display elements that needed external lighting (and a way to diffuse the light so that it is even). Before you know it, professional started equating with heavy. Heavier designs meant larger (and yes, heavier) head mounts.

Not good. 

And not true. At least not for long. By using new types of displays, optics and components, professional is no longer heavy.  New products, such as the xSight weight about 10-12 ounces. Not quite as light as some of the consumer HMDs in the 'Skymall magazine', but getting there.

So will this be the year of the 'good enough' professional HMD that combines wide field of view, high definition and light weight? I hope so, and I think it will.