How does the Glass display project the image onto the lens?

Google Glass uses a Field Sequential Color LCOS to project the rendered image through a lens and into the retina, as first determined by Karl Guttag in March 2013.

Basically, the image of each single color channel is synthesized by an LCOS array on a chip, while the illumination source is rapidly cycled through pure red, green, and blue LEDs, in synchronization with the color channel switching.

Each of these sequential images is passed through a series of lens elements that direct the resultant image to the user’s retina via the Glass display.  The result is that the user percieves a small translucent screen hovering at about arms length distance, as extended up and outward from the right eye. Since the colors are cycling very very quickly, the user perceives a full color video stream.

Here is a diagram of both the LCOS image generator, as well as the RGB lamps, and the lensing system:

structure of an FSC LCOS image generator

The determination of Glass utilizing an FSC LCOS is based on detailed analysis of the Google Glass Fashion Week video by Karl Guttag:

Sequential Red, Green, +Blue Fields Captured From Google YouTube Video DVF [through Glass]


Karl Guttag Glass Investigation:
Google Glass Is Using Field Sequential Color (FSC) LCOS (Likely Himax)

Himax LCOS displays:
: About Himax Display : :

original post: Quora


2 thoughts on “How does the Glass display project the image onto the lens?

  1. Karl Guttag

    Thanks for the reference to my site in your blog. I would like to point out that the diagram you showed with an X-Cube color combiner is not what anyone would use for near eye displays. For near eye field sequential color LCOS, they normally use a stack of films and maybe a Fresnel lens to spread the light from a set of red, green, and blue LEDs (some manufactures have the 3 leds in one package). Then the beam splitter is usually either a flat or curve polarizing “film” (sheet of plastic) that is very low cost and inexpensive.

    I took a diagram from a 2001 patent and labeled the key components. This is not exactly what Google is doing (as the diagram was from back in 2001) but it is probably similar.

    1. acroyogi Post author

      Thanks so much for both the original research and the clarification, Karl!

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