Everything You Probably Didn’t Know About FOV In HMDs

VR headsets have been seeing new life for a few years now, and when it comes to head-mounted displays, the field of view (FOV) is one of the specs everyone’s keen to discover. Valve Software have published a highly technical yet accessibly-presented document that explains why Field of View (FOV) is a complex thing when it pertains to head-mounted displays. FOV is relatively simple when it comes to things such as cameras, but it gets much more complicated and hard to define or measure easily when it comes to using lenses to put images right up next to eyeballs.

Simulation of how FOV can be affected by eye relief [Source: Valve Software]
The document goes into some useful detail about head-mounted displays in general, the design trade-offs, and naturally talks about the brand-new Valve Index VR headset in particular. The Index uses proprietary lenses combined with a slight outward cant to each eye’s display, and they explain precisely what benefits are gained from each design point. Eye relief (distance from eye to lens), lens shape and mounting (limiting how close the eye can physically get), and adjustability (because faces and eyes come in different configurations) all have a role to play. It’s a situation where every millimeter matters.

If there’s one main point Valve is trying to make with this document, it’s summed up as “it’s really hard to use a single number to effectively describe the field of view of an HMD.” They plan to publish additional information on the topics of modding as well as optics, so keep an eye out on their Valve Index Deep Dive publication list.

Valve’s VR efforts remain interesting from a hacking perspective, and as an organization they seem mindful of keen interest in being able to modify and extend their products. The Vive Tracker was self-contained and had an accessible hardware pinout for the express purpose of making hacking easier.  We also took a look at Valve’s AR and VR prototypes, which give some insight into how and why they chose the directions they did.

Open Source Headset With Inside-Out Tracking, Video Passthrough

The folks behind the Atmos Extended Reality (XR) headset want to provide improved accessibility with an open ecosystem, and they aim to do it with a WebVR-capable headset design that is self-contained, 3D-printable, and open-sourced. Their immediate goal is to release a development kit, then refine the design for a wider release.

An early prototype of the open source Atmos Extended Reality headset.

The front of the headset has a camera-based tracking board to provide all the modern goodies like inside-out head and hand tracking as well as the ability to pass through video. The design also provides for a variety of interface methods such as eye tracking and 6 DoF controllers.

With all that, the headset gives users maximum flexibility to experiment with and create different applications while working to keep development simple. A short video showing off the modular design of the HMD and optical assembly is embedded below.

Extended Reality (XR) has emerged as a catch-all term to cover broad combinations of real and virtual elements. On one end of the spectrum are completely virtual elements such as in virtual reality (VR), and towards the other end of the spectrum are things like augmented reality (AR) in which virtual elements are integrated with real ones in varying ratios. With the ability to sense the real world and pass through video from the cameras, developers can choose to integrate as much or as little as they wish.

Terms like XR are a sign that the whole scene is still rapidly changing and it’s fascinating to see how development in this area is still within reach of small developers and individual hackers. The Atmos DK 1 developer kit aims to be released sometime in July, so anyone interested in getting in on the ground floor should read up on how to get involved with the project, which currently points people to their Twitter account (@atmosxr) and invites developers to their Discord server. You can also follow along on their newly published Hackaday.io page.

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Virtual Reality For Alzheimer’s Detection

You may think of Alzheimer’s as a disease of the elderly, but the truth is people who suffer from it have had it for years — sometimes decades — before they notice. Early detection can help doctors minimize the impact the condition has on your brain, so there’s starting to be an emphasis on testing middle-aged adults for the earliest signs of the illness. It turns out that one of the first noticeable symptoms is a decline in your ability to navigate. [Dennis Chan] at Cambridge Biomedical Research Centre and his team are now using virtual reality to determine how well people can navigate as a way to assess Alzheimer’s earlier than is possible with other techniques.

Current tests mostly measure your ability to remember things, but by the time that’s a problem, things have often progressed. The test has the subject walk to different cones and remember their locations, and has already proven more effective than the standard test.

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Safely Dive Into Your Fears With Virtual Reality

What makes you afraid? Not like jump-scares in movies or the rush of a roller-coaster, but what are your legitimate fears that qualify as phobias? Spiders? Clowns? Blood? Flying? Researchers at The University of Texas at Austin are experimenting with exposure therapy in virtual reality to help people manage their fears. For some phobias, like arachnophobia, the fear of spiders, this seems like a perfect fit. If you are certain that you are safely in a spider-free laboratory wearing a VR headset, and you see a giant spider crawling across your field of vision, the fear may be more manageable than being asked to put your hand into a populated spider tank.

After the experimental therapy, participants were asked to take the spider tank challenge. Subjects who were not shown VR spiders were less enthusiastic about keeping their hands in the tank. This is not definitive proof, but it is a promising start.

High-end VR equipment and homemade rigs are in the budget for many gamers and hackers, and our archives are an indication of how much the cutting-edge crowd loves immersive VR. We have been hacking 360 recording for nearly a decade, long before 360 cameras took their niche in the consumer market. Maybe when this concept is proven out a bit more, implementations will start appearing in our tip lines with hackers who helped their friends get over their fears.

Via IEEE Spectrum.

Photo by Wokandapix.

Immersive Augmented Reality On A Budget

By now we’ve all seen the cheap headsets that essentially stick a smartphone a few inches away from your face to function as a low-cost alternative to devices like Oculus Rift. Available for as little as a few dollars, it’s hard to beat these gadgets for experimenting with VR on a budget. But what about if you’re more interested in working with augmented reality, where rendered images are superimposed onto your real-world view rather than replacing it?

As it turns out, there are now cheap headsets to do that with your phone as well. [kvtoet] picked one of these gadgets up for $30 USD on AliExpress, and used it as a base for a more capable augmented reality experience than the headset alone is capable of. The project is in the early stages, but so far the combination of this simple headset and some hardware liberated from inexpensive Chinese smartphones looks to hold considerable promise for delivering a sub-$100 USD development platform for anyone looking to jump into this fascinating field.

On their own, these cheap augmented reality headsets simply show a reflection of your smartphone’s screen on the inside of the lenses. With specially designed applications, this effect can be used to give the wearer the impression that objects shown on the phone’s screen are actually in their field of vision. It’s a neat effect to be sure, but it doesn’t hold much in the way of practical applications. To turn this into a useful system, the phone needs to be able to see what the wearer is seeing.

To that end, [kvtoet] relocated a VKWorld S8 smartphone’s camera module onto the front of the headset. Beyond its relatively cost, this model of phone was selected because it featured a long camera ribbon cable. With the camera on the outside of the headset, an Android application was created which periodically flashes a bright LED and looks for reflections in the camera’s feed. These reflections are then used to locate objects and markers in the real world.

In the video after the break, [kvtoet] demonstrates how this technique is put to use. The phone is able to track a retroreflector laying on the couch quickly and accurately enough that it can be used to adjust the rendering of a virtual object in real time. As the headset is moved around, it gives the impression that the wearer is actually viewing a real object from different angles and distances. With such a simplistic system the effect isn’t perfect, but it’s exciting to think of the possibilities now that this sort of technology is falling into the tinkerer’s budget.

If you don’t want to go the DIY route, Leap Motion has been teasing an open source augmented reality headset which has us quite excited. We’re still waiting on the hardware, but that hasn’t stopped hackers from coming up with some fascinating AR applications in the meantime.

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Leap Motion’s Project North Star Gets Hardware

It’s been more than a year since we first heard about Leap Motion’s new, Open Source augmented reality headset. The first time around, we were surprised: the headset featured dual 1600×1440 LCDs, 120 Hz refresh rate, 100 degree FOV, and the entire thing would cost under $100 (in volume), with everything, from firmware to mechanical design released under Open licenses. Needless to say, that’s easier said than done. Now it seems Leap Motion is releasing files for various components and a full-scale release might be coming sooner than we think.

Leap Motion first made a name for themselves with the Leap Motion sensor, a sort of mini-Kinect that only worked with hands and arms. Yes, we’re perfectly aware that sounds dumb, but the results were impressive: everything turned into a touchscreen display, you could draw with your fingers, and control robots with your hands. If you mount one of these sensors to your forehead, and reflect a few phone screens onto your retinas, you have the makings of a stereoscopic AR headset that tracks the movement of your hands. This is an over-simplified description, but conceptually, that’s what Project North Star is.

The files released now include STLs of parts that can be 3D printed on any filament printer, files for the electronics that drive the backlight and receive video from a laptop, and even software for doing actual Augmented Reality stuff in Unity. It’s not a complete project ready for prime time, but it’s a far cry from the simple spec sheet full of promises we saw in the middle of last year.

A Low Cost VR Headset

Virtual reality systems have been at the forefront of development for several decades. While there are  commercial offerings now, it’s interesting to go back in time to when the systems were much more limited. [Colin Ord] recently completed his own VR system, modeled on available systems from 20-30 years ago, which gives us a look inside what those systems would have been like, as well as being built for a very low cost using today’s technology.

The core of this project is a head tracker, which uses two BBC Microbits as they have both the accelerometer and compass needed to achieve the project goals. It is also capable of tracking an item and its position in the virtual space. For this project, [Colin] built everything himself including the electronics and the programming. It also makes use of Google Cardboard to hold the screen, lenses, and sensors all in the headset. All of this keeps the costs down, unlike similar systems when they were first unveiled years ago.

The ground-up approach that this project takes is indeed commendable. Hopefully we can see the code released, and others can build upon this excellent work. You could even use it to take a virtual reality cycling tour of the UK.

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