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Optics - Part 1

A project log for £100 Google Glass using Raspberry Pi

DIY Google glass but done properly

michaelmcdonnellmichaelmcdonnell 08/20/2014 at 09:010 Comments

Hi its Michael here.  Sorry I haven't posted any updates in a while but I have been out in Egypt for the past month and a half and so have had very little access to the internet.

One of the major challenges in producing a system like Google Glass is the projection of the image so that it can be seen. If there was no need to be able to see through the image our job would have been incredibly simple as all that is needed is the stock high magnification lens that comes with the glasses. However, for our task we have decided that placing the screen to the side allows for a much greater ability for the image to be used simply as an overlay to the real world keep it augmented reality rather than virtual reality.

The main issue we had here was making sure that we could have the screen quite close to the eye while still having the image placed at the infinity focus point and still having the image large enough to see. We played around with various magnifying mirrors and some quite complicated mirror arrangements to try and find an ideal balance. Despite this, even with a 15x mirror, we were unable to properly bring the screen into focus at the desired size. The other problem with this set up is that we would have had to very carefully cut the mirrors to the correct size without affecting their optical properties.

During this experimentation however, we did stumble across one surprising fact. It happened while trying to test a setup of the mirrors and we needed one more which we couldn't find. To resolve this we decided to try using my glasses (for shortsightedness) instead. We found a curious effect that the image produced was far bigger and in fact the focus had been pushed too far away so that we were in fact looking at a virtual image which I could not focus on. This gave us an idea and so we managed to get a hold of different strength glasses and compared their effects on a reflected image. It turned out that the stronger the glasses the greater the magnification and focusing effect, with -3.50 glasses producing a large in focus image at a distance of about 3 inches. Now obviously this is too large a distance to have a reflecting screen from your face but it was still a start.

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