V-Rtifacts

How-To; Teardowns; Tutorials

Mnemonic’s MRG2.2 Upgrade – Augmented Reality + Kinect

Several months ago I shipped off an MRG2.2 to Mnemonic in the Ukraine. He said he wanted to do a few mods and some experimenting. Little did I know that he would put together a totally sweet augmented reality system, where the view inside the VR helmet combined the real world outside the helmet with computer generated interactive 3D objects. Interaction comes through a gyroscopic head tracker AND a Microsoft Kinect. I’ll let the video and the photos explain further:

and here’s what the modified MRG2.2 looks like from the inside and outside:

The Kinect is enabled through FAAST software from the University of Southern California MxR.

WOW!

It’s All In Between The Eyes

If you look yourself in the eyes, you’ll start to realize that your eyes and your head are different than anyone else’s. The spacing between your eyes, known as the interpupilary distance is about 65mm, but this varies from 50mm to about 75mm, depending on who’s eyes you’re looking through. Also the position of your eyes, relative to the shape of your head is unique; some people have eyes that are more inset, or perhaps bulging outward.

The designers of VR helmets have to deal with all this variation in the human phenome. Everyone has a sweet spot where the two lenses of a VR helmet are perfectly aligned with their eyes. Similarly, each of us want the lenses to be positioned as close as possible to our eyes (to achieve wide field of view), without discomfort. If you wear eyeglasses, you need to have room to fit your glasses between your eyes and the lenses.

So… let’s look at how one helmet design deals with these issues:

Teardown – Virtual Research V6

1995 brought us the V6 head mounted display from Virtual Research, the successor to the excellent design of the VR-4. The V6 doubled the overall resolution while retaining the great optics, field of view, comfort, and ease of use originally found in the VR-4. In addition to improved image quality, the V6 refined many of the mechanical elements pioneered in the VR-4, greatly simplifying these mechanical elements. The VR-4 had quite a number of circuit boards inside the helmet, but the control box could have been built completely from Radio Shack components. The V6 moved almost all the electronics into the control box, leaving the helmet with a minimum of electronics.

The V6 manufacturing process did not require any expensive tooling, such as injection molds. The plastic parts are either thermoformed or milled in a machine shop. The metal parts are either stock or machine shop fabricated. Great for short and medium run products! The VR-4 used extremely thin thermoform plastic for light blocks and circuit board mounts. This plastic tended to crack and break off over time. The V6 totally eliminates this thin plastic and uses sheet metal (anodized aluminum) and milled plastic instead.

The V6 was followed shortly by the V8, again doubling the resolution. The V6 and V8 share the same control box, power supply, and mechanical components. The V8 adds a small fan inside the helmet shell to cool the electronics and LCDs. The displays and driving electronics are from Epson.

Specs in the brochure…

3D Photo Tools

If you’ve been into 3D still photos for a while, no doubt you’ve come to love StereoPhoto Maker, a great (free) Windows based tool for aligning, cropping, correcting and adjusting 3D digital pictures. But when you’re done fooling with the pixels, how can you share them with the world? Everybody seems to have a different 3D viewing system.

Not long ago, I ran across Phereo.com, a new (free) 3D photo sharing site (think Flickr, but for stereoscopic images.) You can upload stereoscopic photos in a variety of formats, and then anyone can view them in a wide selection (their selection) of formats and sizes.

Phereo is still in public beta testing, but they’ve said that it comes out of beta on Nov. 1. Looks like it’s hosted on Amazon EC2, so I assume there’s plenty of storage and horsepower to back it up.

Phereo 3D images can be embedded in your own web pages. That alone got me wound up enough to write and publish 3D Pix, a WordPress plugin which handles all the embedding work and upgrades the WordPress post editor with an “Insert 3D Pix” button to make posting super simple.

All these photos were shot with my Fuji W3 at 10 megapixels per eye, but the W3 is the subject of another (forthcoming) post. Until then….

Setup A Fastrak – Fast!

For many years, and perhaps still today, the Polhemus Fastrak was/is the reference standard for low lag, high accuracy six degrees of freedom (6DOF) tracking. Used extensively to track head mounted displays and data gloves, this magnetic tracker was used in most VPL systems and all the 1rst generation Virtuality systems.

For fun, here’s a video showing how to setup and test a 4 sensor Fastrak.

How To Buy LCDs (in 1995)

Jeremy Oliver advises how to purchase LCD displays for your next homebrew VR helmet. (Hint: take all your optics to Montgomery Wards and try every TV and camcorder on the shelf!)

Jeremy’s less than successful experience with Radio Shack suggests a big thumbs down, but what did I know; my first DIY leveraged their Pocketvision-27 (still wondering about models 1-26?)

And now I’ll turn the podium over to Jeremy:

Dear Dreamer and Garage VR Enthusiasts:

DO NOT USE LCDs from the Sega GameGear and/or the Atari Lynx.  They are not NTSC compatible.  The GameGear can be made NTSC compatible with the TV tuner that is an accessory sold separatedly but you will find that you are paying more than for most pocket LCD TVs in the market.  Besides if you went ahead and use a pair of Sega GameGear as viewers for a HMD, I am sure that you will be displease by the coarse resolution.  The Atari Lynx has more res than the GameGear but it is still inadequate for VR immersion.

Using a pair of VictorMaxx Stuntmaster would work but the resolution is even worse.

DO NOT BUY LCDs from Radio Shack.  I am sorry that if some of you would disagree with me on this but I am talking from experience.  One of my first HMD was built from hi-res 3.3″ LCDs I hacked from some pocket TVs I bought from Radio Shack and now it doesn’t work because I can’t find replacement parts that only Radio Shack sold.  I lost about $170 because some small surface mounted diodes and transistors were damaged by my novice soldering skills.

I then lost $30 to long distance phone calls pursuing these parts all over America and even Japan.  I could have easily fixed my damaged TV sets if only Radio Shack was cooperative of giving me the neccessary information I would have needed to make my own power supply to run the LCDs.  This information I seeked was just the values of a handful of crucial surface mounted devices.  Now Radio Shack does not have 85% of the parts I would have needed if the damage was worse.  That is why I say don’t buy from Radio Shack.

STICK WITH THE MAJOR BRANDS like Sony, Casio, JVC, Sharp, etc.  They manufacture their own products and you have a better chance finding parts from them down the road when you may need them (the backlight for example).

HOW TO PICK LCDs:

Go to your local elctronics stores and check out anything with LCDs (e.g.  pocket TVs, camcorders, and even laptops).  Really examine these LCDs if you don’t care what others think take your optics with you.  I would stand in Montgomery Wards really eyeballing the LCD TVs and camcorders with my assortment of fresnel, arcrylic, glass lenses.

Once you make your list, get in contact with as many technicians/TV repairmen you can who are knowledgeable of LCD products.  Ask them what is the complexity of disassembling these LCD products from their housing and modifying them to lightweight and still functional.  Then ask if they have the service manuals to these LCD products in their shops so that you can hopefully see them for yourself.

Service manuals that have many illustrations and schematics will save you alot time, money, and heartaches.  DO NOT BUY any LCDs without looking at its service manual.  This will give you an idea how to strategically disassemble/modify the LCD product for HMD use.  Also try to milk the technician for as much information as possible, I learn more about electronics and video technologies from all the technicians I have met that reading a good book.  They probably can probably give you some better ideas too

Now call the manufacturers for prices of the LCDs, all neccessary parts to give it a composite video signal, and the servie manual.  Try to find out how many years these parts will be available.  I highly advise that you don’t buy soon to be discontinued products because of the uncertainty of available parts.

Once you decide what LCD to use make sure you want to go along and build a HMD because no matter what you still going to spend some money and invest alot of your time putting it together into a decent working HMD.  Really think it over

If you decide to do it…I am with you every step of the way.  If you have any questions just e-mail me.  I even have some circuits that you can put together that will enhance the performance of your HMD.

OH DARN

I forgot to discuss the use of VGA LCDs as viewers for HMD….well you probably have an idea what I was going to say.  If any of you want me to go into that possiblity, feel free to e-mail with that your request.  I pretty sure that I have pissed of some of you with this large byte letter…..I just hope that it was very helpful to some.

Sincerely,

Jeremy Oliver                         foliver@lonestar.utsa.edu

From: “Frank J. Oliver ” <foliver@lonestar.jpl.utsa.edu>
Newsgroups: sci.virtual-worlds
Subject: Re: TECH: Sega Game Gear LCDs
Date: Mon, 25 Sep 1995 20:00:21 -0500
Organization: The University of Texas at San Antonio
Message-Id: <Pine.SGI.3.91.950925185231.28828C-100000@lonestar.jpl.utsa.edu>

LEEP On The Cheap

Build your own LEEP style wide field of view head mounted display optics. Check out the instruction video and parts list below.

In the late 80’s and early 90’s wide field of view head mounted displays were all the rage; immersion was everything! The dominant HMD vendors, VPL Research and Virtual Research shared the same optical implementation: lenses from LEEP Systems. These wide angle optics (designed by Eric Howlett of LEEP), coupled with 2″ or 3″ LCD screens really did deliver a totally immersive visual experience…except that the resolution of the LCDs were so low that under this extreme magnification each pixel looked like a football; you were swimming is a sea of colored footballs!

LCD Screens and LEEP Optics

By the mid 90’s (and up to the present) a primary design criteria for head mounted displays was small size and light weight. Indeed there are entire head mounts that weigh only a few ounces and look almost like sunglasses. Sadly, immersion and wide field of view were abandoned. The new generation of head mounts had 20 – 30 deg. field of view. You felt like you were looking through a distant window.

For reasons which I will cover in a forthcoming post, wide field of view and small/light head mounted displays are mutually exclusive. Anatomy and physics bars the way.

Almost 20 years ago I demoed an early Virtual Research Flight Helmet complete with LEEP optics. Being very impressed but unwilling to drop six grand into my first head mount, I set about building my own. The Radio Shack LCD TVs that I found were very similar to the Sony TVs in the Flight Helmet and I set about installing everything in a Friday The 13th style hockey mask. The optics were my biggest challenge, but the answer was buried in Eric Howlett’s LEEP patent, not as a claim, but as a demonstration of how to achieve wide FOV with conventional optics.

So… here’s a brief video recreating that optical design from 1991. I’ve cheated a bit by using my Android phone as the LCD screen, but otherwise the optical path is essentially the same. Aside from the phone, there’s about $25 in parts for a single eyepiece and it can display almost 90 deg. (diag.) field of view. The lens mounting is extra cheesy, but it demonstrates the optics quite well, and only takes 5 min. to assemble. So without further ado…

In the video I mention that someone needs to write an Android application to make it into a fully tracked head mount. After editing the video I remembered and tried out a couple of popular Android apps: Google Sky and Layar, both of which use the position sensors for a full 3D view. They work great with this lens system!

Parts List:

  • Anchor Optics Plano Convex Lens AX73263 43mm dia. x 77.0mm FL – $10.50 (Eyepiece)
  • Anchor Optics Double Convex Lens AX73424 62.8mm dia. x 72.4mm FL – $13.50 (Objective)
  • 2″ PVC Coupler
  • Small Sheet of Polystyrene plastic – 0.030 Black Sheet

If you were building this for real, you’d spray paint all the plastic parts to a black matte finish. LEEP also beveled the edges of the eyepiece lenses to make a better fit with the nose. To reduce weight, switch from glass lenses to CR39 plastic lenses.

If you assemble 2 of these with LCDs, you may find that the eyepieces are too far apart to match your eye spacing. Simply turn the two optical assemblies so that the LCDs point slightly outward and the eyepieces come closer together. Then apply 3M Press-On Fresnel Prisms.

Build Your Own 3D Shutter Glasses Controller for Field Interlaced Stereoscopic

There are tons of stereoscopic DVDs and VHS tapes on the market encoded as field interlaced stereo. Also, one of the easiest ways to make 3D video is with a camcorder (NTSC or PAL) and a NuView 3D adaptor (often selling on Ebay for less than $100.) For those of you who want to watch on a good old fashioned television, shutter glasses offer excellent 3D (but with some flicker.) Another use for NTSC/PAL shutter glasses is to preview on a field monitor when shooting 3D video.

3D glasses (wired) are a dime a dozen these days, but how do you synchronize them with the video fields of an NTSC or PAL TV signal. Today’s project shows you how to build and package a control circuit to do just that. It is simple and cheap, and the packaging is mighty rugged.

This fine example (pictured above) has endured about 7 years in the field shooting under all sorts of uncomfortable conditions. Its been to India, Thailand, Honduras, Mexico, Dominican Republic, and North St. Louis, to name a few.

Looking at the connectors and controls from left to right:

  • There’s 2 BNC connectors for video. They’re just a loop through. Plug your NTSC or PAL video source into either connector and your monitor into the other. The shutter control box will sense the video sync without altering the signal on the way to a color monitor.
  • The first toggle switch lets us reverse which image goes to which eye. Sadly, there seems to be no standardization of field interleaved stereoscopic video with respect to which video field gets which eye’s view. This switch lets us put either field to either eye.
  • The second switch turns the power on and off. In addition to an internal 9V battery, the control box can run off a 9-12 VDC wall wart or even a Anton-Bauer power pack.
  • The jack on the right is for external DC power. There’s a small green LED above it to let us know when the control box is turned on.

The control box will work with any brand of shutter glasses with a 3.5mm stereo mini plug such as the glasses shown below.

So… let’s get to the actual circuit. Fortunately it is quite simple; just 2 chips and a few other components. The metal case and toggle switches are the most expensive part of this project, but don’t worry, it isn’t much.

Shutter-Schematic

A quick description: Video comes in on the left through a coupling capacitor (C4) into an LM1881 sync separator chip. One of the outputs of this IC is an ODD/EVEN signal – binary logic for video field 1 or video field 2. Toward the right a CMOS 4030 quad exclusive-or chip is configured as a fast square wave generator. The frequency isn’t overly important, 500 hz to 1 khz is fine. The shutters on the glasses are made opaque by this square wave. The ODD/EVEN signal modulates this square wave flipping the shutters on and off. Opposing signals are generated for left and right eyes. A DPDT switch reverses the connections to the 2 shutters in the glasses.

The first few of these that I built were hand wired on perf board, but eventually I moved over to a printed circuit board. You can download the layout as a PDF. For short runs you can use Press n’ Peel Blue to make the board. In order to keep this a one-sided PCB, there’s 2 jumpers: J1 and J2. Don’t forget to install them.

The hardest part of the project is manufacturing the enclosure, mounting the parts and wiring everything up. Its just time consuming. I used a Hammond 1590B metal box which is virtually indestructible. You’ll need to drill holes for all the jacks and connectors. Measure each connector carefully. Aluminum is soft and you can drill all the holes with a small hand drill. Drill everything before starting to mount and wire things. Brush out all the metal shavings before starting with the components.

The PCB is just tacked down with double sticky-sided tape (the thick foamy type.)

You MUST keep the sleeve of the 3.5 mm shutter jacks insulated from the metal case. If you’re using a plastic case, you can use any old stereo jack, but with a metal case you’ll need special ones like these (above.)

Wiring up the switches, BNC connectors, and power jack is straightforward. Just follow the schematic. You can substitute panel mounted RCA jacks if you don’t like BNC.

I used kynar (wire-wrap wire) for all the signals and 24 gauge stranded for all the power.

The battery holder clip is held in with a 4/40 screw, nut, and lockwasher.

Parts Sources