HMD Project – Part 6

Prototype Alpha

From pre-purchase research I knew that none of the projectors on the market would focus at a distance close enough to produce a 33mm image.  This was the reason I demolished those projectors, you see.  Lenses, from proper optical suppliers, cost a packet, £20 – £60 a pop for the budget ones.  Not knowing anything about optical engineering I knew that I would need a selection of lenses to try out.  Having broken my fair share of IT equipment, I knew that projectors contained plenty of glass stuff.  See; I’m not so mad.

An image with a 4:3 aspect ratio, which has a diagonal size of 33mm, according to Pythagoras, or at least my wild interpretation of his theorem, will be 27mm X 20mm in size.  So, this is the target.

33mm image from pico

33mm image from pico

Well, that wasn’t so hard, now, was it?

As you can see that image is about 7cm away from the projection source, so I am going to have to use a mirror, in order to mount the projector vertically.

I made a test mount, using a mirror from one of the projectors, obviously.

Mirror mount

Without too much effort, I was able to get the pico steady and aligned, and an image around the size I wanted:

image via mirrorimage via mirror

By Jove! We may be onto something here.

Without further ado, I attached the rig, somewhat precariously, to the headset, just to see.

To stabilise the paper & foam based modelling  material, I used a base-board of 3mm acrylic.  By the way; at this stage I was beginning to realise that glue guns rock!

prototype mountedprototype mounted

Now to turn it on… Ouch!  Turn it off, turn it off!  Lower the brightness, set lamps to eco-mode and try again.

VR4 prototype displayVR4 prototype displayVR4 prototype display

Not bad.  Not too bad at all.

Now I just have to workout how to mount two of these buggers, and a VGA cable without breaking the current optic mounts.  It’s also worth noting, that since I bought two different projectors to scrap, none of the lenses, or mirrors are the same – which could be interesting.  Also these Samsung projectors have a few drawbacks which I’ll highlight in the next part… suffice to say, they have caused me to swear.

I also need to find a rear projection material, I have tried all sorts, but so far nothing gives anything like good enough results, even pro-grade film is very grainy.  This issue may result in a complete re-designing.

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2 Responses to HMD Project – Part 6

  1. Leeroy says:

    Seems to me like you rock. Yes, I’m quite sure you rock very much.

    I’m very disappointed in the market of “pico projectors” because the concept is poor. You’re not often in a room with no ambient light and with a decent sized plane surface and a place to set your gear. Brightness sucks, screen sizes are modest so you can’t show it to a lot of people… It’s broken.

    Now VRDs, now we’re cooking. I’d like to try and build a helmet featuring a half-silvered mirror catching a laser image (from something already available like Microvision’s ShowWX)… so that I can have heads up display information while riding a bike! B-)

    That’s because I’m still waiting for Brother’s AirScouter and Microvision VRDs, and I won’t like paying a lot of money for the hip factor and the very low weight. I don’t care about extremely low weight because I favor mounting to a helmet to flimsy little glasses.

    Basically I’ve never tried retinal projection of a virtual image and I really want to know it’s doable in real life scenarios.

    Applications like navigation, Augmented Reality overlay, text display, etc would really achieve their potential with virtual retinal display technology.

  2. Leeroy says:

    … but uhmm – it’s critical the the image be see-through.
    And of course on a helmet the display would be retractable, you’d flip it out of your way when you don’t want to use it (and want a clearer view at the real surroundings).

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