Apple Wins a Patent for an advanced Head-up-Display that could project Holographic Imagery across the Windshield & Side Windows
Today the U.S. Patent and Trademark Office officially granted Apple a Project Titan patent relating to a vehicle's Head-up-Display. The twist in Apple's invention is that the Head-up-Display could be used on the passenger side portion of the windshield as well as vehicle side windows using a holographic optical element.
In Apple's patent background they note that vehicles such as automobiles are sometimes provided with head-up displays. Typical head-up displays project images onto the windshield of a vehicle. A driver of the vehicle can view the projected images while driving.
Head-up displays are typically used to display vehicle status information such as speedometer information. Head-up displays allow information to be safely displayed for a driver without requiring the driver to look away from the road ahead.
In conventional head-up displays, a virtual image is created by using a display in a dashboard to project light onto the front windshield of the vehicle at a given angle of incidence, which then reflects the light to the driver's eyes at an angle of reflection that matches the angle of incidence.
Since the position of the front windshield is generally a fixed design parameter, the display in the dashboard is precisely positioned to direct light towards the front windshield at a specific angle of incidence so that the light correctly reflects off of the windshield towards the driver.
Traditional head-up displays of this type can place undesirable restrictions on the location of head-up displays in the vehicle. For example, a conventional head-up display may be incompatible with the side window of a vehicle because light reflected off of the side window from a display reasonably mounted within the structure of the vehicle does not reach the user's eyes due to the law of reflection.
It would therefore be desirable to be able to provide improved head-up displays for displaying information for the occupants of a vehicle in a wider range of locations.
Apple's invention covers a head-up display that may include a display unit that produces the display output and an optical combiner on a vehicle window that directs the display output towards the viewer.
The optical combiner may be a holographic or diffractive optical element or may be an array of angled reflectors such as micromirrors embedded in an index-matching material.
Optical combiners formed from holographic elements may be configured to reflect light at an angle of reflection that, if desired, can be different than the angle of incidence, thereby allowing light to reach a viewer's eyes even when the head-up display reflects light off of a side window in the vehicle.
The diffraction order spacing of the holographic optical element may be controlled to reflect a given input angle to a desired output angle.
A holographic optical element may include volume holographic media such as photopolymers or holographic-polymer dispersed liquid crystal in which a reflective hologram has been written (e.g., using the interference of two lasers).
The holographic element may be a single layer that has been written with one or more colors or may be multiple layers where each layer has been written with one or more colors.
The holographic optical element may be non-switchable (e.g., may include a permanently encoded hologram) or may be switchable (e.g., may be adjusted by applying an electric field).
Optical combiners formed from angled reflectors may also be configured to direct light towards a viewer even when the optical combiners are formed on side windows of a vehicle. Each reflector in the optical combiner may be angled such that light is reflected off of each individual reflector according to the law of reflection and is directed towards the viewer's eyes.
Apple's patent FIG. 1 below is a side view of an illustrative vehicle with a head-up display; FIG. 3 is a side view of an illustrative head-up display on a side window of a vehicle.
To dive deeper into the finer details of this invention, review Apple's granted patent 10,866,414.