In the last few years, head-up displays (HUDs), which project information onto the driver’s view of the road, have started appearing in a few high-end cars. But a more compact kind of projection device, small enough to fit inside a rearview mirror, could see this kind of display more widely deployed.
The new projection device, developed by Light Blue Optics, based in Cambridge, UK, uses a technique called holographic projection that allows it to be far smaller than current in-car HUD systems.
Details of Light Blue Optics’s prototype were presented at the Society for Information Display’s Vehicles and Photons 2009 symposium, in Dearborn, MI. The prototype projects an image through a two-way wing mirror so that it appears to be about 2.5 meters away, superimposed over the reflected road scene. The picture appears to originate from a point in space in front of the mirror, only from a narrow perspective.
Holographic projection uses constructive and destructive interference of light to make up the picture, allowing the device to be much smaller.
Holographic projectors use liquid crystal on silicon (LCOS) to modulate beams of red, green, and blue laser light to create a complete image. Holographic projection does not actually involve creating a hologram, but rather uses principles of holography to create a projected image through optical interference.