Polarized Projection HMD

[STRZ]

My idea for an HMD was to use dual pico-projectors and polarized lenses. That way each eye can get its own screen and you can adjust and overlap the views as much as you want (physically) which would solve a lot of the issues of using either 1 screen or 2 separate LCDs.

Good idea, where do you get pico projectors capable to project an image small enough and with sufficent resolution? The minimum i found on the consumer market is 5.9" 480p 1:1 throw ratio ( Microvision Showwx+ laser projector )

They offer kits for developers to embed into a device http://www.microvision.com/pico_project ... index.html" onclick="window.open(this.href);return false;

In the end of this year they plan to launch a 3d 720p green laser pico projector, and when it's available and not overly expensive i'll try to make a HMD.

A mini curved screen about 6 inch away in front of a helmet to fill the view you would get through a visor, and maybe demagnifying glasses/lenses if focusing is to difficult was a idea i had. To blend the projectors and warp the image i'd use immersive display lite 2 wich can be bought for 50$

Maybe a naive plan compared to what others do, but why shouldn't it work?

[Bishop51]

Yeah, the whole high resolution Pico market is going to change design possibilities in a radical way I think. I think you're all bang on about the curved screen and polarized lens setup. That's the future right there (well, that is until they FINALLY start manufacturing affordable, flexible OLED technology). That's what bugs me about the major players out there, Sony, LG and others have high resolution, flexible screens working in the labs yet VR doesn't seem to be on their radar for potential uses at all.

[PalmerTech]

Split this off from the PR2 thread, since it merits a place for dicussion.

One of the difficulties I have experienced with this design is that it is quite bulky, and puts weight pretty far away from the face. Part of that is because I have insisted on using rear projection, though.

[WiredEarp]

I'm still fairly sure you will need some sort of lenses in there to increase the virtual distance between your eyes and the screen. I believe focusing at 6" will cause eyestrain very quickly. Put your head up 6" away from your monitor and see how long you find it comfortable!

Re minimum throw distance, couldn't additional lenses be placed inline of the output lens to change the focus on LED pico projectors? Or, swap out the current lens entirely. I dont know if this would be possible with a laser based one however...

[STRZ]

Re minimum throw distance, couldn't additional lenses be placed inline of the output lens to change the focus on LED pico projectors? Or, swap out the current lens entirely. I dont know if this would be possible with a laser based one however...

In fact the laser ones from Microvision have infinite focus, meaning that you have not to adjust focus it if changing distance. Maybe that there is some tolerance to go smaller if the image doesn't get to bright.

Contrast is oled like with those lasers, really stunning. The only disadvantage is visible specle with the current model ( the new ones should do it better ).

Front weight wouldn't be a problem i think, because the screen will be mounted to a motorcycle helmet wich can be balanced easy.

Don't know if any flexible fresnel like glasses exist wich work the reverse way as the fresnels, to mount instead of the visor in front of the projection screen. But it wouldn't disturb me having a bigger screen further away away in front as long as it doesn't interfere with my arms holding the steering wheel or the wheel itself. Important is that it fills the FOV you get through a Racing Helmet.

I would mainly use it for racing sims, that's a very cool genre for HMD stuff or if not to say the genre wich best translates from reality into VR i'd say. Having a high periphal vision there give you an edge over your opponents aswell because the fastest reaction is dependent of your subconsciousness if you drive looking ahead like you should driving a car.

Check out C.A.R.S wich is currently still in alpha stage and can be had for 10$, a sim with state of the art graphics, already good to get hooked with simracing.

[youtube-hd]http://www.youtube.com/watch?v=wJnGbJgO ... KRUJOghsvA[/youtube-hd]

[brantlew]

Whoa, that's pretty sick! I don't even play racing sims but I wanna play that.

[STRZ]

It's an open community project ( Community assisted racing sim ), with liitle amount of cash you can join there and make sure the implement some state of the art headtracking features. ith a membership ( basic membership is 10€ ) you get the right to download alpha and beta builds.

Everbody can bring in ideas into this sim, later when it's done and ready for sale you get cash in relative to what you have invested, meaning that you most propably earn cash because when it's released it will be a sureshot.

It would be awesome to see implementions for VR coming from the scene itself, meaning from this forum

http://www.wmdportal.com/" onclick="window.open(this.href);return false;

[ERP]

I looked at this a while ago I couldn't come up with a reasonable way to physically package everything.
You'll need some sort of optics to adjust the throw ratio of the projector this is relatively easy enough if you use laser projectors. There offset is also less than ideal for mounting, usually 50%.
You'll also need a screen and some sort of optics to make viewing that screen comfortable.
Nice thing is the screen can be relatively large and curved which reduces the magnification needed you can probably get away with a single lens. That lens will still need to be mounted close to the eye if you want wide FOV.

As for polarization there will already be some in the output, so it may not be as simple as just sticking two filters in front of the projectors, you may have to use two aligned filters and a quarter wave retarder to rotate the polarization of one of the projectors.

[STRZ]

You'll also need a screen and some sort of optics to make viewing that screen comfortable.

Could something like this be any useful for focusing the big screen? http://www.rothervalleyoptics.co.uk/ant ... d1952.html" onclick="window.open(this.href);return false;

[Bishop51]

A lot of this can be accomplished with a single high res fresnel (3dLens f550) cut down to a wide format strip (something like a ski-goggle lens) and bent in a slight curve across the entire viewing plane. I have a few of these lenses and they bend with minimal distortion quite nicely. You can stick one roughly 6" from a monitor, put your nose up to it and have a very comfortable viewing experience.

The Pico's should probably be side mounted left and right and then projected out onto a curved screen. The great thing about this format is that the screen could be made very lightweight and you could push it out much further than a standard HMD. Some lightweight connecting rods to hold it out and a nylon light blocker stretched over the whole framework. If I can find some time I'll sketch something up!

The biggest hiccup would be working out the projection optics so that they can fill the screen this close and from a side mounted position.

The absolute best thing about this setup is that it would play nice with bread and butter display standards both 2D & 3D. It truly would be a plug & play HMD.

[STRZ]

A lot of this can be accomplished with a single high res fresnel (3dLens f550) cut down to a wide format strip (something like a ski-goggle lens) and bent in a slight curve across the entire viewing plane. I have a few of these lenses and they bend with minimal distortion quite nicely. You can stick one roughly 6" from a monitor, put your nose up to it and have a very comfortable viewing experience.

Yeah, that was what i was thinking of, good to know

The Pico's should probably be side mounted left and right and then projected out onto a curved screen. The great thing about this format is that the screen could be made very lightweight and you could push it out much further than a standard HMD. Some lightweight connecting rods to hold it out and a nylon light blocker stretched over the whole framework. If I can find some time I'll sketch something up!

I know what you mean, i have some constructions pictured in my mind, one of my first posts here i linked a YT Video from where i actually picked up the projection idea with the side mounted picos, since then i can't get this idea out of my head. Any input appreciated though, nice to have now some theorical progress

The biggest hiccup would be working out the projection optics so that they can fill the screen this close and from a side mounted position.

This could be done with image warping software i think, focus wouldn't be really a problem if using laser projectors. I thought in cross projection, the left pico onto the right half of the curved screen and the other one on the left overlapping each other a bit for soft blending using the warping software as well. Around 150° is possible this way with very little distortion due to warping the image correspondingly. It's like the big dual projector setups only small sized.

The absolute best thing about this setup is that it would play nice with bread and butter display standards both 2D & 3D. It truly would be a plug & play HMD.

Indeed.

But 3D isn't mandatory for me, if it's doable with the current laser picos without compromising FOV or resulution then it's great, but i prefer a higher resolution + high FOV, even if it is only 2d. My knowledge of what's doable with 3d using non 3d pico projectors is very limited though.

[cadcoke5]

I wonder if the idea of bouncing the projection off of a spherical mirror would help with the throw-distance issue. The idea has been used for video projection in planetariums. This guy has a really detailed FAQ about the subject, including both optical and software issues.

http://paulbourke.net/miscellaneous/domemirror/faq.html" onclick="window.open(this.href);return false;

Actually, he probably has much more technical information than you really want to know if you click his name at the top of the page.

As for the mirror itself, the planetarium folks need to get something fairly large. But, for a HMD, you obviously need something in the range of an inch or two diameter. Perhaps just getting a magnifying lens and then applying reflective coating would allow you to pick your own mirror specifications, since lenses are available in infinite variety. You can find coating instructions on many web sites. A small stick-on panoramic mirror, sold to stick onto your car's rear-view mirror would be a cheap way to experiment.

I am uncertain of how using a spherical mirror effects the focus distance. I.e. does it actually move the focus distance closer or further away?

A variation on the idea might be a cylindrical mirror.

For the eye optics, I had suggested just using normal reading glasses. They are available at Dollar stores, and have a variety of strengths. Even if you are young enough (or near-sighted enough) to not need them to view the image, using them would force your eye to focus on the image as though it were farther away. Normally, your eye's convergence and focus work in coordination with each other. It may be that violating this significantly would cause problems.

Regarding the field of vision through glasses. Many people are already used to having the world outside the perimeter of their glasses be out of focus. If the same thing happens in a HMD and their peripheral vision suffers, I don't think that is a significant problem. Though, I think it would be nice to have the image larger than the glasses field of vision.

Joe Dunfee

[WiredEarp]

Good point re the glasses FOV!

I've been thinking about using mirrors rather than optics to increase the fov etc myself... do mirrors cause the same color abberations as lenses can?

[PalmerTech]

Good point re the glasses FOV!

I've been thinking about using mirrors rather than optics to increase the fov etc myself... do mirrors cause the same color abberations as lenses can?

No, they are much better than lenses if you can manage to use them. Mirrors are great.

[WiredEarp]

Interesting, thanks PalmerTech. Another question - I believe you mentioned in another thread that optics are expensive due to molds etc having to handle cooling etc.

I was wondering, would it be possible to use a 3D printer to create lenses without all the hassle and expense of molds? I appreciate that there could well be issues with melt heat, etc, but it might well avoid the problems with heat, since you could build up the lens a layer at a time. No idea if home 3D printers would have sufficient resolution, but if not it could still be worthwhile for a company to use a higher res printer to do this, and they could then do limited lens runs for other people, without all the expense of molds etc.

[ERP]

Interesting, thanks PalmerTech. Another question - I believe you mentioned in another thread that optics are expensive due to molds etc having to handle cooling etc.

I was wondering, would it be possible to use a 3D printer to create lenses without all the hassle and expense of molds? I appreciate that there could well be issues with melt heat, etc, but it might well avoid the problems with heat, since you could build up the lens a layer at a time. No idea if home 3D printers would have sufficient resolution, but if not it could still be worthwhile for a company to use a higher res printer to do this, and they could then do limited lens runs for other people, without all the expense of molds etc.

The reason Lens are expensive is the molds have to be very precise, the same would be true of any additive method.
I don't know of a 3DPrinter even high end ones that could get even close to the accuracy required.

[WiredEarp]

I thought that would be the potential downfall. However, this might change in the future (3D printer quality, at least commercial ones).

Even with the current limitations, I wonder if you could print the lenses, then do a grinding stage to finish them off, just like homemade telescope makers make their lenses and mirrors by grinding them by hand.

Really shooting out stupid lens ideas now, but a 3rd idea would be to get flexible acrylic film molds made and fill them with a fluid with the right optical properties, saving all the hassle of molding the vast majority of the lens. Just a little bit stolen from Dr Laser, since I saw him in a vid use a oil filled, acrylic lens he made himself to replace a multi thousand dollar 'real' lens.

[STRZ]

A cousin studied biomolecular optics, now studying quantum optics, i should ask there

Do you mean this? http://vimeo.com/9168335" onclick="window.open(this.href);return false;

[WiredEarp]

Similar sort of thing, yep. Actually, those glasses are a pretty great idea for people in the developing world, since they can just be adjusted to work right for the user without needing eye tests etc. Although they wouldn't be able to correct astigmatism, they could still definitely help improve many peoples lives, who might not have access to optometrists etc.

[mAchiNE]

Interesting thread!

A lot of this can be accomplished with a single high res fresnel (3dLens f550) cut down to a wide format strip (something like a ski-goggle lens) and bent in a slight curve across the entire viewing plane. I have a few of these lenses and they bend with minimal distortion quite nicely. You can stick one roughly 6" from a monitor, put your nose up to it and have a very comfortable viewing experience.

FYI the f550 is no longer available from 3dLens.com I ordered some lenses form them at the end of last year and it was not on their site anymore and when I inquired about it they said they no longer sell it and they only had one left, which they sold to me.