Given the FOV im after and the screen size double mirrors will be very difficult i think. I need a few more mirrors to play around with. AT least i know how to make front surface now if i find something usefull.

How did you find the gigaware projector? I didnt hold much hope of use for a hmd, any chance of a mini passive setup with 2 or just not enough lumens? Have you had a look inside to consider brighter leds?

Ive also ordered a cheap vga-tv converter box and a 3.5 inch reversing lcd to play with

Radioshack sells the Gigaware projector for $99. I saw one, saw it had VGA and was 640x480, so I pulled the trigger. I actually bought it to use for HMD experimentation, truth be told... Mini passive setup would be very interesting. The problem is, the lumen output is already really low. Yes, there are brighter LEDs out there, but they need fan cooling and eat a lot more power, and the gain is really not very high (The LED in it is actually already far more powerful than most consumer garbage). Right now, I am trying to figure out how possible it would be to make a rear projection setup, one projector for each eye. The guts of the projector are very, very light, so it could be mounted as far as a foot or so in front of the eye and still not be a huge issue. Basically, I would want a small dome of rear projection material for each eye, and have each projector mounted in front of it. Rear projection helps hide screen door effect from low resolution, so might actually work decently.


You have no idea how many LCDs and bits of optical display I have picked up over the past years, especially these past few months. I work on portable game system conversions, but this HMD hobby has me working hard. I am just terrible at documenting it.

What really excites me is those new laser based PicoProjectors. Boy oh boy do I want to get one... I have some serious plans laid out.

I know, I'm so close to pulling the trigger on the Show WX (which just came out). I'm sure it could be useful somehow.

You could use penta prisms. They reflect at 90 degrees and don't flip the image. However, those things might be too heavy and too expensive. You might want to look at internet surplus stores for used optics to pay less. I'm not sure it would work in an hmd because you could look toward the wrong surfaces of the prism.

Another solution would be to use two regular mirrors. You could have the screens on each side of your head pointing forward, one mirror would reflect the light 90 degrees toward your nose and the other mirror would reflect toward the eyes. Reflecting two times will flip the pic twice so it will not get flipped. You can use 90 degrees prisms instead of mirrors to get better picture quality. It might not work if the light path is too long for your optics.

Some pics added.

I don't really get how this works. You would have to mount those huge displays on a helmet and scale the image with some lenses to be far away, but seem large to the eyes to focus them.
I don't understand how such an optic works. Can someone explain this "prism"- solution
I would love to build such a HMD on my own. I have a budget of ~ 1000Euro.
I want a resolution like 1280x720 and >40° FOV.
I search desperately to find small, but high res displays. Getting something like 640x480 or 800x600 does not really make sense as i could get a vr920 or z800.

If anyone could post working hardware, i would build it.

My current problem with this build is not the focus but that the screens together are too wide overal. This means my eyes need to point outwards for it to work. I have yet to do more work either with prisms or mirrors. I am also waiting on a 3.5 inch lcd for testing.

Check these displays here- http://stores.shop.ebay.com.au/VitroLig ... QQ_armrsZ1

You could go for the vr920 or z800 but you would be better of with a 3d 22inch monitor as the view will be bigger.

Does it need to be 3D capable? Okta has a great project here, but I have a 1280x800 HMD with 85 degree FOV that I made using a heavily modified MRG2.2. It is not done, but I can finish it up pretty fast, it is already in the "working fine" stage. Would you be interested in it? If so, PM me.


I wish you luck Okta, update us when you can!

I have a 22 inch iz3d monitor at the moment.

Of course the HMD should be 3D. This is the most important point. Hey we are at MTBS3D here! I don't think the MRG can be modified to stereoscopic.

I had a z800 and sold it because it hat so bad game support. Now 2 years later it doubled in price and we have iz3d drivers now.
I thinking about rebuying one but it has so low resolution and the support in iz3d driver does not seem to work perfect as i read.

The link you posted for the ebay displays has only low resolution displays. The best resolution/size choice would be the 4.8inch 1024x600 display, which is still rather large.

Can someone post optics which would fit such a display? I don't have any idea how to place a display so close to the eyes and make it focusable by the eyes. Is there some technical document available here at the forums to understand how HMD optics work.

I have a few magnifying glasses at home and made a simple try with those. Besides magnifying they also makes it possible to view things at a closer distance but at a cost of distortions in the periphery. The lenses needs to be kept closer to your eyes than the display to work properly.
If i use more than one the viewing distance decreases but i also get more distortion. I don't know if you can circumvent this by using different lenses.
So i guess you should only need a pair of convex magnifying lenses but you'll also get peripheral distortion. Do anyone know if you have this using standard hmd's?
I can't say i know too much about optics on higher levels than this so leave this open for other suggestions!

The most higher quality Stereo-HMDs have multi-lens setups per eye (e.g trilpets), so they are using a combination of different lens characteristics to obtain a wide FoV while still
providing an almost distortion-free picture.

Without deeper knowledge of optics i don´t see a possibility to resemble such a system in a Diy-manner.

When using a (stereo) single lens system you have to come to a compromise, that would be edge-distortion, lower FoV and lower resolution.

The minimum you would like to have here should be 640x480, that limits the display choice to displays 3,5" and above (if you want to keep the price somewhat low, this includes 1000$)

One of the better ones should be the Primeview PD035VX2.
With an active area of 72,0mm x 52.56mm you know that you should look for lenses that aproach these measures.
The display should preferably be even a little larger than the lens itself for better FoV.
Suitable lenses tend do to between from 8 to 20 diopters (2x-5x Magnification) with a focal length of roughly 5cm-10cm.

When using larger Displays, e.g. the 4,8" 1024x600 unit, you will most probably need some sort of prisma in addition to your magnifying lens to shift the two images together.
(Thats where the science starts... )

Eschenbach offers some high quality acrylic lenses that would fit 4,8" or larger displays.

If you want to experiment with lenses i would go with plano-konvex / bi-asperic /aspheric type of lenses. There is almost no way around playing with different kind of lenses to actually see what they can exactly do for you.

I decided to go the monoway (quite similar to palmers mod) since it can provide a more rewarding immersion because i prefer the wide FoV and higher Resolution over the stero3d.

Okta said that one of his most immersive experiences was with a large fresnel very close to his face in front of his monitor. I have just received different sized fresnels and did the similar, very impressive! I watched a gameplay video of an upcoming Sci-Fi Game (Black Prophecy) this way and the feeling of being there in the cockpit was so great (even though my handheld setup did miss some major keys for immersion ). 3D just can´t do this for me.

This is all a big "Afaik" since i just recently started reading and experimenting with such things.

If found the LeepVr.com Page especially useful for better understanding from the basics to the guts of an HMD. Very good!

I think it is next to impossible to diy a wide fov, high resolution stereo 3d headset without some very special tools, deep knowledge of optics and a big wallet for the two micro hd displays. But i wish everyone luck who tries nevertheless!

A very interesting HMD was the discontinued Wide5 by Fakelabs. From the looks of it they we´re using quite large displays, but i could never find any detailed technical documents.

Greetings,

Sin

Great post, SinSilla!

The real problem is not designing the optics, the knowledge is not too hard. Getting the right lenses made, though? That is the hard part... Lens fabrication is not something you can DIY easily, and making a mold for acrylic lenses costs tens of thousands of dollars.

I has also come to the conclusion that stereo3D is not possible to DIY with good specs at a decent price right now... Okta, I have been playing a bit with front surface mirrors, I think that is the key here. Basically, construct a box with two high res LCDs facing towards each other, and use matched size, light front surface mirrors to redirect the view towards the face, with circular magnification optics for each eye. Might be a bit fiddly to get working, but I know it is possible; Try researching some of the 3D photo viewers out there that use printed slides. Might even let you use our 7" screens! And actually, rear surface mirrors are probably fine for initial experimentation.

I had this idea with 3D Fotoviewers at the very beginning, however the fotos are very small which need also so small displays.

2 ideas:

1. What if we use a head mounted 7'' high resolution display and standard nvidia shutter infront for each eye. I guess the problem is to find a 120hz display of this size.
2. Mount 2x 7'' displays at 90° with a semi translucent mirror and go for a polarized setup.

1. Yeah not much chance of 120hz screens at the moment.

2. Nice idea! First problem for me is that none of my fresnels can be used becuase they destroy polarization but i will give this some thought, cheers!

What is so special about the Fresnet? Can't we use simple magnify glasses.

I think a simple glass at 45° in between the two displays whould be sufficient becaus everything is dark inside the HMD?? So one would need a special semi transparent mirror.

Anyone knows how the 7'' displays are polarised?

I pulled out some realD glasses and it seems they block the light on my screen when held at a 45 degree angle so it seems possible. Hopefully ill be able to give this some more time soon.
I have very little experience with polarized so it will be interesting.
Can anyone recommend cheap large filters say 100mm square?

Fresnels are special because they are very thin and light, but still manage to give a decent magnification even at large sizes. It´s pretty hard to find affordable lenses which would suit a 7" display. There is one 140mmx100mm bi-aspheric plastic lens (magnifies by 2) that i´m aware of that could be used somehow theoretically. But it costs 80€ each.

But fresnels do come with a drawback, the color reproduction and sharpness of fresnels, compared to other lenses, is decent at the utmost.

And btw, just wanted to let you guys know that Vitrolight offers the Hydis 5,6" 1280x800 for 150$ since a few days, no more need to pay 340$ (which would admittedly get you a much better controller, but it´s really huge).

@Okta

Don´t they say that cellophane foil can be used for changing polarisation? I would give it a try, i guess you should have some in the kitchen. ^^

Cellophane sometimes can work like a decent retarder. Which means that one foil gives you circular polarization and yet another gives you linear polarization. Depending on how you rotated them you can adjust the resulting polarizationangle at your own wish. An almost as good shortcut is usage of a simple retarder followed by a polarizer. This works well for rotating polarization up to 90°.
If you need to retain a "sharp" polarization you always need to use an extra polarizer after the retarders. Have yet to try simple cellophane but most household plastics i've tried didn't have a special polarizationalignment. They simply only messed up the polarized light.

Did some playing today and it looks like plannar mirror left/right is the way to go. Next trip to the hardware i will look for some long hinges to mount the screens and mirror together and start tuning.

Sounds good! Do you still use the 7" screens for this setup?

Yup same screens, one in front, other on right or left. Will need counter balancing.

Just curious; Why a side by side, as opposed to a 90 degree top/bottom setup like most planar display set ups?

LOL! You might end up like this guy:
http://3dvision-blog.com/diy-virtual-re ... -tracking/

Oops i didnt mean planner rather just stereo mirror. I think it will be easier than didling around with polarizers and a silvered glass. But im still open to trying it out at this point.

EDIT: Woops, never mind.

Octa, check this up, if you didn't saw it yet!
http://www.vrtifacts.com/hmds/leep-on-the-cheap/

That looks pretty cool. Unfortunately it doesnt appear that setup could work with 3.5 inch creens which are the smallest i can find at the moment. I am also wary of teh 3m fresnel sheet to provide enough offset.
I wish i could play with all those available lenses to get the size and focul distance right for 3.5 inch screens.

Anyone knows of any kind of optics emulation application? Something that would plot the paths of the light rays as they go through the lenses? That would make your life a lot easier.

Ide guess the resolution is in sub pixels and no info about a vga driver board

Playing with more lenses i am almost to the point i could use 2 3.5 inch screens tight together but the available ones have a 10mm or so bezel at the edges making it even harder >:(

My meccano will arrive soon and i will have a crack at some mirror setups,

Im intent not to let this go as i can see no help on the horizon from industry.

Big fov 3d hmd or death!!

Nope, not sub-pixels. That is a QHD display, exactly a quarter of the pixels contained in a full 1080p image. It looks perfect!

The only place I can find that will sell in low quantities wants over $900, though.

Hey man, any progress? Just wanted to check in.

Oh, and I have a favor for you, check your PMs!

Ok its not looking good. Ive tried several setups with mirrors and the best solution is single mirror left/right. The problem with using mirrors is that it increased the space and gets in the way of large lenses and makes teh resulting fov too small for what im after. Also having 1 mirrored screen means closing one eye during normal operation which is unacceptable.

Still more playing around with lenses to see if 3.5 inch screens are viable.

I never pursued this, but suspect the ideal solution is a front-surface concave mirror. I have no idea how such a mirror would behave when using it at an angle. Perhaps a lady's compact magnifying mirror would be a good test.

Joe Dunfee

Check out this article about military HMD's. This picture shows a curved clear mirror, apparently reflecting a display on the side of his head.

http://vresources.org/node/2468

Joe Dunfee

Update on OP.

Jon, not sure whats going on with that hmd?

It is just straight up reflecting an image from two screens using glass, maybe with a 20-30% mirror coating. Not high FOV or immersive, but useful for superimposing stuff on a real view.

Looks like great progress! Did you ever figure out the real native resolution of the screen?

Yeah i think they're 800x480.

Gotcha. Think you might try a non-fresnel lens? Your rig looks very modular for that.

Teh fresnels im using i scored at a 2 dollar shop. absolute bonus find as they are about 6.5 inchs and is seems you need to be pretty close to the screen size. Although they are very course and ruin the image a lot they are the best i have for now.

The biggest glass lens i have is a sqare 80mm one that is great quality but only about 3x. The killer with any lens for a single screen like this is it has to be BIG. You cant really use one lens for each eye as it adds convergance and each eyes ends up seeing its own side of the screen only so they lens needs to be big enough for both eyes to see through.

Are you using something different i can try as the imagine quality would be heaps better im sure?