Arduino Glasses a HMD for Multimeter

My lipo finally arrived.

And charging ...

The main challenge was to build it with easy to find parts, but the lens is a problem. I had a pair of perfect lenses (the lens on the right. A plan convex lens with a size of 33mm and a FL of 100mm), but these are difficult to find. In China I had the possibility to buy them by 100 pieces min. order.
So I took the weekend for a few optical tests and the winner is.... the lens of my magnifying head glasses. There are 3 lenses in the set, but the one we need is the big one with a magnifying of 3,5.

The frame of these head magnifier will be used to hold the data glasses.

And the price of the whole thing is about 10$.

It has a focal length of 12cm so that the way from the screen to the lens will be 8,1 cm, with a magnifying factor of 3,. On picture 2 you can see how I found the focal length.

I made the data glasses work, but it was more a trial an error challenge. So I took a google crash course in optics.

First of all I had to understand the difference between a real and a virtual image with lenses. Then a very important thing is, that a human eye can only focus an object with a distance of min 25cm.

And all what I needed was this formula (1/f) = (1/s2) + (1/s1) where f is focal length of the lens s1 is object distance to the lens and s2 is the distance of the virtual image.

I will build now Version III based on this calculation.

Today the result of my lenses tests. All the easy to find lenses does not give the result I want.
The only one which works is the one from the video, the lens from a cheap Chinese 3d viewer.
Problem is, that I have no technical data about this one, what makes it difficult to rebuild the glasses for other users, so that I ordered 2 other models of lenses for testing.

I found the time to try 2 lenses. Google cardboard lens and another one laying around here.
The google lens is not the best choice, so I will try a few other lenses
Here now the B2 version with lens and screen mounted. Works but I'm still not satisfied

Version II of my Arduino Glasses. Again build out of cardboard. Goes much faster than a 3d Printer (if I had one)
I added a sort of clip to attach it to the glasses. Hopefully I will add the lens and the screen this evening.

Now it's sure, the Google cardboard lens has a shorter focal point. So I had to redesign my prototype and it seems to work. Need to cut the lens.

It seems that the lens I used is not the same as the lenses in a google cardboard.

This is not what I wanted, I want to build this item that everybody can rebuild it.

I used for my first prototype, witch works, a lens from these cheap 3d glasses.

And this was the testsetup.

And now I has to redo the tests with original google cardboard lenses.

There is still a little ghost picture in the screen, so that I try another optic system. Looks better for the moment, but I have to change the lens -> screen setup.

I searched and found a lens with f=45mm, and I trimmed it to the correct size.

I could not resist to test it instantly, and the result is stunning. I tried to photograph it, so that you can imagine the result.