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Need advice on my DIY FPV HMD project

Posted: Mon Apr 15, 2013 9:35 am
by Grix
One of the first things I wanted to do with the rift when after I heard about it was fly FPV aircrafts. However, I was very disappointed when I found out that this was not possible with the rift, at least not without modifications and pretty costly signal adapters. (If you want to read about it, see http://www.mtbs3d.com/phpBB/viewtopic.php?f=140&t=16366 )

Therefore I looked into making a DIY HMD made specifically for immersive FPV flying. And by immersive I mainly mean higher FOV than the usual Fatshark goggles etc. They just look like a big screen in front of you, nothing like the experience the rift offers.

After some research, this is what I'm thinking:

Two of these screens, one for each eye: http://www.aliexpress.com/item/NEW-High ... 60928.html
It's a pretty goofy screen, and not exactly the lightest, but a single screen like the rift uses is too much trouble, one would need software to modify the video into SBS images etc. etc.
Pros for the screen I linked:
1) Extremely cheap,
2) Perfect size (Distance between the centers of the two screens next to each other are almost exactly 65mm, a normal IPD),
3) Decent specs (640*480 per eye is pretty much the highest an FPV pilot will need), and
4) it takes direct RCA input which is what the video receiver uses. The only thing I regret is that it could be lighter and less bulky.

I haven't decided on lenses yet. Does anyone have any ideas? At first I was thinking these: http://www.ebay.com/itm/251148139033
But they are pretty expensive.. With international shipping they cost almost as much as the screens. Are fresnel lenses better, maybe? The image quality doesn't need to be perfect, it's not like FPV video is super HD..

I guess foamcore and skigoggles should work as a housing.

Then I was thinking splitting the image from the video receiver to both screens using a simple RCA splitter adapter.

Total cost is only around $120.

Would this work? Would you guys change anything?

Re: Need advice on my DIY FPV HMD project

Posted: Tue Apr 16, 2013 3:42 am
by Grix
Bump.. Does no one have any input? Should I just order everything and hope it works?

Re: Need advice on my DIY FPV HMD project

Posted: Tue Apr 16, 2013 4:13 am
by geekmaster
I bought two of those screens from amazon, which were listed as 920 pixels horizontal resolution, after seeing a youtube video of it used with a Raspberry Pi, and all the tiny text during bootup was quite readable.

But my two arrived with HORRIBLE resolution. I opened one, and looked up the part number of the LCD panel, which was only 320x240 (not enough to work with a RasPI). I complained to amazon, and they yanked the product specs from the listings for that product (for all sellers). They said I could get a refund, but the return shipping would be a significant part of the purchase price, so I kept them.

So beware of the resolution, since new units seem to be substituting a MUCH lower resolution LCD panel...

I also bought a pair of fisheye backup cameras at the same time, for FPV use.

Re: Need advice on my DIY FPV HMD project

Posted: Tue Apr 16, 2013 4:34 am
by Grix
Damn.. That pretty much spoils this plan. There are proper 3.5 inch 480p panels out there but they are very expensive, $100 each. 5 inch screens are cheaper but I don't think it will be easy to get 100% stereoscopic overlap. I would be easier to just find a solution for the rift I guess.

Re: Need advice on my DIY FPV HMD project

Posted: Tue Apr 16, 2013 10:02 am
by geekmaster
Grix wrote:Damn.. That pretty much spoils this plan. There are proper 3.5 inch 480p panels out there but they are very expensive, $100 each. 5 inch screens are cheaper but I don't think it will be easy to get 100% stereoscopic overlap. I would be easier to just find a solution for the rift I guess.
There may be old stock somewhere, with the old high-resolution LCD panels. But good luck finding them. You really need a photo of it showing a screenful of text (like RasPi boot messages) to see if it is an old unit. The new ones are worthless for text or fine detail. And near the eyes in an HMD, those pixels would look like an RGB checkerboard!

Re: Need advice on my DIY FPV HMD project

Posted: Tue Apr 16, 2013 4:25 pm
by PalmerTech
Those 320x240 screens are everywhere, we use them on ModRetro all the time. They are dirt cheap, but not much use for VR.

The legitimate 480P displays are all in the $80+ range, there are none that can compete on price with those dirt cheap QVGA res panels.

I would not rule out using the Rift. A fast capture card feeding into a well optimized video player could have pretty low latency.

Re: Need advice on my DIY FPV HMD project

Posted: Tue Apr 16, 2013 4:44 pm
by geekmaster
The LCD displays are bought are the exact ones shown in this YouTube vid (from links to amazon at his website):

http://www.youtube.com/watch?v=HR-qS_ZHn0o

The YouTube product specs listed it as 920 pixels horizontal res (and the text is readable as you can see in the video above).

The ones I received were only QVGA, and the RasPi boot text is completely unreadable (just two or three pixels per letter).

It would be nice to find the ones show in the video. The price did seem "too good to be true", but apparently some people did get the better displays at that low price.

Re: Need advice on my DIY FPV HMD project

Posted: Tue Apr 16, 2013 5:51 pm
by PalmerTech
The text does look reasonably legible in the video, I am about 90% certain that the screen he is using is QVGA, though. I have used that exact same model of screen before.

Can the size or font of the boot screen be altered? Perhaps you are experiencing some other problem? I have played SNES games on these screens, and despite the low res, fine text is pretty readable.