The A and O of this project is the Lens.
I need to create a virtual image at a distance of min 25cm, so the eye can focus the screen.
So the focal length and the magnification factor are very important.

A google cardboard lens with a focal length of 45 mm will be the first lens for my test, even that the magnification factor could be a problem. So the calculations are one thing the other one is.... just do it :)

To calculate the lens, I use this link