New display technology for 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.
A head-up display (HUD) overlays information on a normal view of the road. For example, symbols can be used to show the car's current speed or the distance to the vehicle ahead without the driver having to look away from the road.
The new projection device, developed by Light Blue Optics uses a technique called holographic projection that allows it to be far smaller than current in-car HUD systems.
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.
Existing HUDs require relatively large liquid-crystal arrays and optics to generate an image. In a BMW 5 Series, the size is about five litres. The new device is about one-tenth of the size.
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. The technology could work equally well on a forward-facing display such as a windshield.
