[REQ] First steps to build a HMD?

[Issus]

Hi Guys,

I've been lurking here for awhile reading what I can however I'm having troubles figuring out where to get started. Unlike most people on here I'm not aiming for high resolution or stereo (even though it might be nice) as i'm just wanting to display composite video. I've been using a pair of goggles with very poor lenses and Kopin .44" displays (EStar EVG920) which have really bad blurring in the corners and a chromatic aberration. I also have a pair of Emagin Z800's but they are very impractical for using with composite video, especially outdoors.

I realise this is a forum for 3d enthusiasts but as far as I can tell, its the best place on the internet for discussions about DIY HMDs!

So, my aim is to make a HMD that is 640x480 resolution and I'm hoping to get a clear picture across the whole display. 40 degree FOV would be fine, but up to 60 degree FOV would be amazing.

I've found some suppliers of cheap LCDs however the smallest 640x480 displays haven't been 3.5" which I'm thinking is going to be too big?
Is there a place to get these smaller? I'm thinking 1.50-2" would be perfect.

I haven't been able to find a good place to find mirrors or lenses (but I haven't looked very hard either at this point). I'm not sure what optics I'll need though.

For now, my idea is to use two displays (which will let me do 3d later if I want), one for each eye mounted at right angles to my line vision, pushed as far back towards my ears/temples as possible in order to keep the forward area as small as possible. I was thinking that with 45 degree angle mirrors in front of the eyes this will give me the best HMD size? I can put the electronics between the V of the mirrors hopefully.

Is there a need for lenses between the eye and the mirror, or the mirror and the display?


I'm hoping to be able to do a very good build here, as a mechanical engineer friend who is a genius with SolidWorks will be helping me out (and hoping to get me to pay for a set of HMDs for him too haha). I have a large CNC router which can machine even small pieces to extreme accuracy (designed by said friend, built by me), a manual metal work lathe and I'm working on a 3d plastic printer (FDM type, hoping to have it working in a month). I've also got vacuforming tools and do a bit of rocketry stuff so I'm familiar with composites to make enclosures and parts from too. I really love designing and building my own things rather than using some store bought things that don't quite do what I want!

Really hoping the awesome community here can help me figure out the bits and pieces required to make an awesome HMD come to life!

[Issus]

So, i found these optics:
http://www.thorlabs.hk/NewGroupPage9.cf ... up_ID=4847
So far, thats the only place I've been able to find who sell online and are not us-only. The pricing isn't horrible but is certainly not too cheap. Still not sure what lenses I would need exactly, or how they would need to be configured. I'm guessing what I'm after with the lenses is to gain magnification, as at about 4" total distance with my described setup and a 3.5" lcd, I'm looking at only 27.6 degrees vertical FOV. This means, at about 2x magnification (if this is possible) I'd be hitting my target pretty much dead on.

So, is 2x mag too much to ask for? Would my view be getting too distorted?


For the mirrors, I've only found this site: http://www.fsmirrors.com/
It looks really terrible but the prices are much better than anything i can find on ebay! Thorlabs also sell convex and concave mirrors, but they are extremely expensive. If i could get a slightly convex mirror it could increase my FOV, or being that it's on an angle - it could completely destroy my view (and set me back a lot of money!)

http://www.ebay.com/itm/3-5inch-TFT-LCD ... 4603392ad1 appear to be what I want for a LCD. 3.5" appears to be the smallest size readily available for a 640x480 display.

[WiredEarp]

I use my Z800s for composite view, pretty cheap to get an AV converter... I have no issues with it (use it for FPV).

Re building a HMD, I think its about 2.5" that is the sweet spot according to PalmerTech iirc. Basically, a PR/Rift type design using 2 side by side screens is what you are wanting to build. I was tossing up the idea myself as it solves quite a few issues with the Rift, however, with the progress ive seen of people working on Rift drivers etc, it doesn't really seem that necessary. Also, the screens in this size are not amazing resolution unless you pay a lot (I think 800x480 3" was the best I could find when I looked), although prices on everything drop quickly and these screens are being used more in pseudo SLR type cameras. PalmerTech is leveraging the more reasonable prices of bigger displays (2x the size) and the fact that modern 3D uses SBS display (awesome idea) to bring the prices down on his solution and simplify the design.

Of course, if you build a cool one using mirrors, that would rock. Theres another guy on here who is making his own mirrors for a high FOV hmd. I think the problem is you will have trouble finding mirrors of the sizes/shapes you want...

[Issus]

My z800's have sunburn on one oled so not very good for motion as you have a black dot on the display

I was thinking of getting mirrors to the general outer dimension I want, and then perhaps using my CNC router to vscore the cutouts I want so they can be snapped off. I've never tried glass in the mill though, so I have no idea how it would go. I'm wondering if I can buy a cheap acrylic mirror and take the protective paint of the back of the metallised section with acetone or similar to give me a mirror. I realise that if the mirror manufacturer did their job properly this will give me a tin layer rather than silver, so it will tarnish over time but it would be a lot easier than glass as plastics are so very easy to machine.

I can't find a screen smaller than 3.5" with 640x480 resolution - as I've said I'd love to go smaller but it just doesn't seem possible right now with consumer level purchasing. If I was a big company I might be able to get something from sharp or someone... but I'm stuck with the Chinese suppliers and they appear to be years behind the game.

I looked at using a single larger display mounted in front, however whilst much cheaper this is a far deeper HMD, meaning more bulk and more weight out in front. I'd also need to get some sort of beam splitter or pentprisms to get my eyes to focus in the middle, rather than having to go crosseyed to look at the display A single 3.5" display would be awesome from a cost perspective though. If I could figure out the parts for this, it would be easier!

Side by side displays would need a 1280x480 lcd, and some sort of computer I guess to duplicate the image - I don't think this is technically feasable for me.

[Issus]

So, I Found this software, which looks like it does exactly what I want, but the base version costs $2500!
http://www.radiantzemax.com/en/zemax/zemax-se.aspx

Way out of my price range for this project. Has anyone come across a similiar, perhaps cheaper (<$100?) or free piece of software?

[Issus]

So, I found a telescope website that linked a bunch of different software, some of it is even free!

OSLO (http://www.lambdares.com/) looks pretty good, the EDU version is free for up to 10 elements which should have me covered perfectly!

http://www.skyscientific.com/index.htm
dbOptic also looks OK, and is under $100.

On the other end of the spectrum, up with Zemax we have OpTaliX (sounds like a 13 year old's player name I know!) At 2500CHF this is more than my yearly hobby budget just like Zemax.
http://www.optenso.com/index.html


Also of interest is this: http://savannah.gnu.org/projects/goptical
As a software guy, this could be made to accurately trace out exactly what i want, and maybe even trace it out pixel by pixel so i can see exactly how my picture would look. Sounds like a lot of effort though and i'm lazy.

[Fredz]

Why don't you simply use a 3D modeler that supports ray tracing for rendering ? Blender fits in this category and is free, you can simply model your lenses, affect them a refractive index and use textures to simulate the displays.

[Issus]

Thats a cool idea, I didnt realise you could do that I'll have to figure out what format solidworks can export as to get it to show up in blender.

I assume I'd want to position the camera where I expect my eye to be?

Thanks for the idea!

[Issus]

So it looks like 3.5" is the smallest LCD I can get with 640x480. I found an amazing 800x600 0.97" OLED, with a fantastic interface electrically that would have allowed really easy driving with composite video... alas it cost $1500 at a 1000 unit volume. Way way out of my budget. The cheapest 640x480 seems to be about $80 in single volume which better suits my project (actually the same one i linked to above on ebay.)

Now I need to figure out some optics, I think i'll need to get a book or two on it, as I'm struggling to find the information I need freely online

[cadcoke5]

I posted about this in another thread, so sorry about repeating it. www.surplusshed.com sells used lenses and has a pretty large inventory that is all cataloged. Prices are typically $4, and shipping is $5, regardless of number of lenses ordered.

Joe Dunfee

[Issus]

Thanks Joe, unfortunately I still don't know what lenses I need, plus, I'm not in the USA.

[Issus]

So I finally went ahead and ordered one screen + driver board. I figure this will give me a chance at seeing it physically so I can work out how to position the screens and then I'll look at getting some books on optic design

[PalmerTech]

I can send you some glass optics that will get you 46 degree FOV out of your current 0.44" displays, let me know if you are interested.