Gleaning the Prism

Category : Life through Glass, Photo & Video · (3) Comments · by May 24, 2013

The Google Glass prism is a fascinating piece of technology, but how does it work?  Read on and learn more…

Prism new2

Martin Missfeldt created this infographic to describe how the Glass prism works.  The graphic is from February, before Glass was available to anyone outside Google.  Martin’s theories were based on the Glass patent and various other sources listed at the bottom of the graphic.  However, I suspect he did not have the benefit of seeing a good photo of the Glass prism (like mine) which might account for this major oversight.


This image has been posted hundreds of thousands of times (according to a Google image search), even on popular tech sites like Mashable, but has anyone noticed this?

Glass Angle

The angle of the screen is backwards!

The relationship between the prism and the eye is not really accurate either.  Here’s a photo of me looking through Glass.  Compare it to the illustration above.  The screen was positioned for best visibility before the photo was taken.

Glass Worn 1

Here’s another look:Glass Worn 2

And why is the face of the prism directly across from the projector curved convexly and mirrored?  You can see how reflective it is in this shot below:Prism new B

Perhaps it was mirrored to deflect sunlight that would otherwise diffuse the image on the screen.  Or maybe it’s so inquisitive people like me can’t look into the projector.  But that doesn’t explain why that surface is convex.

So how does the prism work?

Well, there’s a reason I started by saying “Read on and learn more” instead of “Here’s the answer”.  There are currently several players in the wearable tech game and I don’t think Google wants to expose their hand quite yet.  I’m sure many companies hope to copy the Glass prism, and while imitation may be the highest form of flattery, flattery doesn’t win the game.


(3) comments

[…] I noticed a surprising revelation about the Glass prism and how it works.  Details and more photos on GlassAppZ: […]

[…] Reshared post from +Laura Ockel I noticed a surprising revelation about the Glass prism and how it works.  Details and more photos on GlassAppZ: […]

8 years ago · Reply

The mirrored and curved end controls the focus point of the display. The light goes through the slanted half silvered mirror, hits the end and is focused back on the half mirror and into the eye from the left side. When drawing light rays remember that the angle of incidence must equal the angle of reflection.

On the original diagram the diverging rays hit a flat mirror and should then continue to diverge rather than converge as shown in the diagram.

Leave a Reply

Your email address will not be published. Required fields are marked *