Patent Application
20180321490
The disclosure relates to a display system for a motor vehicle, and, more particularly, to a head up display system for a motor vehicle.
Many automotive HUDs fall into one of two categories: windshield HUDs, where the projector is below the dash and the projected light is reflected from the windshield to be seen by the driver as a virtual image outside the windshield; and combiner HUDs, where the projector is mounted above the dash, and the transparent combiner through which the driver sees a virtual image is separate from the windshield. For styling purposes, there is reason to prefer a windshield HUD since the projector is hidden and there is not a separate combiner. The absence of a projector and combiner above the dash may also help meet safety requirements. However, the conventional shapes of some vehicle windshields do not allow a conventional windshield HUD to be implemented. For example, trains and buses often have large flat windshields. Race cars often have windshields with a low rake angle.
Conventional windshield HUDs utilize reflection from the front and back surfaces of the windshield. Such HUDs require the HUD projector to be located below the dash in a specific location. Some vehicles have windshields that do not allow a windshield HUD to be implemented. More package volume may be required than is available. An increase in the field of view of the HUD image increases the package volume required for the HUD projector.
Conventional windshield HUD packages often require more volume beneath the dashboard than is available. The required volume increases as the field of view increases. For a conventional windshield HUD, the HUD projector must be under the dash surface, where a ray from the driver's eye to the virtual image reflects from the windshield down to the dash. Typically, this location is close to the steering column.
Combiner HUDs are separate units, with a transparent combiner other than the windshield. However, combiner HUDs introduce styling issues and may make it more difficult to meet head-impact safety regulations.
HUDs that use a diffractive combiner in or on the windshield appear to have many of the same benefits as the present invention. However, when the sun shines on the diffractive combiner, it creates an effect in which the sunlight is separated into its various colors. The resulting artifact is distracting to the driver for particular directions of the sun relative to the vehicle. Because the present invention does not use diffraction, there is no such effect with the present invention.
The present invention may provide a windshield head up display (HUD) in a motor vehicle including partially reflective facets in or near a windshield. The partially reflective facets may direct light from a projector to a person's eyes, to be seen as a virtual image outside of the windshield.
HUD systems that use an array of microlenses on or in the windshield are superficially similar to the present invention in that such a system can be designed so that light from a small projector is seen by the driver. However, the faceted reflector according to the current invention directs the reflected light in a specific direction (typically not the direction light reflects from the windshield surface), while a microlens array spreads transmitted light into a range of angles.
In one embodiment, the invention comprises a motor vehicle including a windshield having a plastic layer sandwiched between two glass layers. The plastic layer has a partially reflective element therein. The partially reflective element passes a first portion of light received from a first direction and reflects a remainder of the light in a second direction. A projection arrangement projects a light field onto the partially reflective element such that a reflected portion of the light field is visible to a driver of the motor vehicle as a virtual image.
In another embodiment, the invention comprises a motor vehicle including a windshield having a glass layer with an outer surface and an inner surface. A plastic layer is attached to the inner surface of the glass layer. The plastic layer has a partially reflective element therein. The partially reflective element passes a first portion of light received from a first direction and reflects a remainder of the light in a second direction. A projection arrangement projects a light field onto the partially reflective element such that a reflected portion of the light field is visible to a driver of the motor vehicle as a virtual image.
In yet another embodiment, the invention comprises a motor vehicle including a windshield having a glass layer with an outer surface and an inner surface. A plastic layer is attached to the outer surface of the glass layer. The plastic layer has a partially reflective element therein. The partially reflective element passes a first portion of light received from a first direction and reflects a remainder of the light in a second direction. A projection arrangement projects a light field onto the partially reflective element such that a reflected portion of the light field is visible to a driver of the motor vehicle as a virtual image.
An advantage of the invention makes it possible for a HUD to be used with any windshield, regardless of the windshield's size or angle of orientation.
Another advantage is that it may provide a HUD system with a smaller package size for a given field of view, or a bigger field of view for a given package size.
Yet another advantage is that there are more locations at which the HUD projector can be installed.
A better understanding of the present invention will be had upon reference to the following description in conjunction with the accompanying drawings.
This invention is not limited so the HUD only displays a video image of a scene. As is known to the art, the image displayed to the driver may include text information, icons, symbols, or diagrams. The information displayed may include information such as vehicle speed, warning icons, navigation cues, and vehicle status. The information displayed may also be related to the scene viewed by the driver through the windshield, commonly known as augmented reality or a contact analog display, and the displayed virtual image may related to the driver's view of nearby objects.
The use of separate reflective surfaces for imaging, such as the facets, instead of the inner and outer surfaces of the glass as used in the prior art, may provide extra freedom and flexibility to optical designs incorporating the present invention. The extra freedom and flexibility may enable one or more of the following: implementing a windshield HUD in vehicles in which this would otherwise be impossible because of the shape of the windshield; reducing the package volume of the HUD projector; placing the HUD projector in locations under or around the dash where it would not be possible if the light were simply reflected from the windshield surface; and increasing the field of view of the HUD image that can be seen by the driver for a given package volume of the HUD projector.
One way to implement this invention is to use optical design software such as Zemax to create multiple optical designs for HUDs, each with a combiner, that step the distance from the driver's eye to the combiner. The combiners in all the designs may fill the volume of space to be occupied by the portion of the windshield that is to be used to reflect light from the projector to the driver to be seen as a virtual image. The intersection of the sequence of combiners with the volume to be occupied by the partially reflective facets may be determined. The combiners may need to be spaced close enough together to prevent noticeable gaps between the facets.
The partially reflecting surfaces can be created by: (1) using the optical design to fabricate a metal surface with the facets; (2) injection molding plastic to fabricate a transparent plastic part with the facets; or (3) over-molding with another polymer having a different index of refraction so the facets have the desired reflectivity. A coating of one or more films of controlled thickness may be deposited on the facets in order to enhance the reflectivity. The coating material may be one or more films of a metal, a metal oxide, a ceramic, and/or a polymer.
In one embodiment, the driver sees light reflecting from multiple facets along the line of sight. Optionally, the reflectivity of a facet may vary as a function of position, to avoid the perception of an edge to individual facets.
The foregoing description may refer to “motor vehicle”, “automobile”, “automotive”, or similar expressions. It is to be understood that these terms are not intended to limit the invention to any particular type of transportation vehicle. Rather, the invention may be applied to any type of transportation vehicle whether traveling by air, water, or ground, such as airplanes, boats, etc.
The foregoing detail description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom for modifications can be made by those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention.
This application claims benefit of U.S. Provisional Application No. 62/500,040 filed on May 2, 2017, which the disclosure of which is hereby incorporated by reference in its entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 62500040 | May 2017 | US |
