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Understanding Google Glass


As Google Glass edges closer to becoming everyday augmented reality, we're curious to know more about how this new kind of connected camera works. 

We're grateful to Martin Missfeldt for breaking the technology down in an easily digestable infographic format. As he'll demonstrate below, Google Glass uses a mini-projector to transmit a semi-transparent prism directly to the retina within the eye.


Total comments: 6

The frame looks very crude and bulky.

The projector should be in the middle.

Think about it.



Infographic (Feb. 2013) is outdated. Figs. 2,4,5&6 of the infograph no longer reflect the glass project. Part 3.

Consider the (plane) reflecting surface inside the "glass cube", in front of your eye. In the 2nd. patent, the light 1st is transmitted through this, is reflected from the curved mirror, and then when coming back is reflected into the eye. How is this implemented (one way transmitted, other way reflected) ? Using light polarization. The (plane) surface is sensible to polarization and transmits one linear polarization while reflecting the "other linear polarization" (at 90 degrees). In the google glass’s 2nd patent, there is a quarter wave plate which is a layer into the optics that rotates the linear polarization by 90 degrees, in reflection.

This optical technology is not new. Google glass's 2nd patent optics is the optics inside a CD/DVD reader (same cube, one way transmitting other way reflecting; same quarter wave plate function), with a different function.


Infographic (Feb. 2013) is outdated. Figs. 2,4,5&6 of the infograph no longer reflect the glass project. Part 2.

You can see the differences between the 1st. and 2nd. Google glass patents from the images:
Go to the illustration of the evolutionary design in the end (the one with the sun glasses). Can you see that the reflecting surface is at 90 degrees, compared to the one in the infografic ? Can you see the end curved surface ?


Infographic (Feb. 2013) is outdated. Google glass currently implements an evolution of its 1st patent (US20130044042; infographic), supplemented by a 2nd patent (US20130070338; optical details).

The difference between the optical details in 1st (Fig.5) and 2nd patents (Figs.2&3) is that, in the 1st the image is directly feed into the viewers eye while in the 2nd is first retroreflected from a (curved) mirror-like surface, plus a quarter wave plate.

So the 2,4,5&6 figs. of the infograph no longer reflect the glass project.

In the 1st patent, the image is directly reflected into the viewers eyes. In the 2nd first it is reflected from a curved mirror-like surface which effectively puts its image in infinity. However, its rays are not allowed to go to infinity, since they are forced to be reflected into the viewer eyes. This is desirable since it relieves the stress from the eye: the eye needs not refocus.

wim hoppenbrouwers

thanks for sharing.



Very simple and clear explanation, many thanks to Martin!
It would be nice to correct the two typos, though (nerv, directely), so as not to mar the overall impression...

Total comments: 6
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