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After working for a year in stealth mode, holography pioneer and auto head-up display (HUD) developer Envisics showed off their advanced solution at CES 2019. I missed that demo, but the company invited me to their Detroit office to discuss the technology. What I saw was clearly the best auto HUD I have seen to date.
Today, almost all HUDs are image-based. An automotive HUD creates an image on a direct-view or microdisplay and then “projects” the virtual image to a fixed focal plane, typically at the front of the car. The Envisics approach uses a custom developed spatial light modulator (SLM), which is a modified microdisplay, designed to manipulate the phase of light. A hologram of the image you want to display is computed and the hologram pattern is driven to the SLM which is illuminated by a laser or LED.
The new second approach has the advantage of allowing all the light to be used in displaying content instead of blocking a lot of light as with the image-based approach. The downside can be the heavy computational load needed to calculate the phase hologram.
In our discussion, Envisics CTO Dr. Jamieson Christmas explained that you don’t want to compute the hologram by simply taking the Fourier transform of the image. That creates an amplitude hologram which is optically inefficient and has a large zero-order component – which manifests itself as a bright spot in the middle of the display.