3D HUDs Drive Automotive Progress
The 3D Heads-Up Display (HUD) is just one of the photonic-based technologies revolutionizing the driving experience of tomorrow.
September 25, 2024 by Coherent
As the automotive industry evolves, the integration of advanced technologies has become crucial to enhancing safety, convenience, and the overall driving experience. One such innovation that has garnered significant attention is the 3D Heads-Up Display (HUD). Combining photonics, optics, and laser technologies, 3D HUDs represent the cutting edge of in-car display systems. Here we’ll learn about how HUDs work, how they’re built, and what future trends are likely to shape them.
Heads-Up Display Basics
A 3D HUD is a type of augmented reality (AR) display which projects critical information into the driver’s visual field, allowing them to read it while still keeping their eyes on the road. Automotive HUDs are similar to head-mounted AR displays, but with one very clever twist. Instead of requiring the viewer to wear glasses, they use the vehicle windshield as the “glasses” to combine the display output with the real-world view.
As a result, the HUD display appears as a “virtual screen” that seems to float in the driver’s line of sight, typically a few feet (one to two meters) in front of the windshield. Integrating the HUD display into the real-world view reduces driver distraction, namely, the need to look away from the road to read dash mounted displays.
A display engine creates an image which is projected out using various lenses, mirrors, or both, on to a combiner integrated into the windshield. The driver then sees the reflection of the projected display superimposed on their normal view through the windshield.
Photonics: The Heart of HUDs
Photonics, the science of light generation, manipulation, and detection, is central to the functionality of HUDs. Key photonic elements in HUD displays include:
Laser diodes and LEDs are primary light sources. Laser diodes, in particular, are favored for their brightness, efficiency, and compact size, enabling the creation of high-resolution displays. By combining red, green, and blue laser diodes, full-color displays with wide color gamuts and high brightness levels are achieved. |
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These optical structures guide light from the source to the display surface. Advanced materials and fabrication techniques ensure minimal light loss and high image quality. |
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These include lenses and mirrors that manipulate light to create the desired image. Diffractive optical elements (DOEs) are often used to achieve precise light shaping and steering. |
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Beam Steering |
Solid-state beam steering mechanisms, such as micro-electromechanical systems (MEMS) mirrors, enable precise control of the laser beams, creating dynamic and high-resolution images. |
Optics: Shaping the Visual Experience
A variety of other optical components play a pivotal role in projecting the HUD image onto the windshield (and then on to the driver’s eyes) while maintaining clarity and focus. These optical elements include:
Projection Lenses |
These lenses magnify the image generated by the light source, projecting it onto the windshield at a size that is easily readable by the driver. |
The combiner is a partially reflective surface that overlays the projected image onto the real-world view. Advanced combiners use holographic optical elements (HOEs) to ensure high transparency and minimal distortion. |
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These non-traditional lens shapes allow the optical system to more readily correct for the curved shaped of the windshield. This results in more compact and efficient HUD designs, enhancing the field of view and image quality. |
3D HUDs
Traditional HUDs show 2D information – that is, they look like a phone screen, tablet or any other flat panel display. The next exciting development in HUDs is 3D (stereoscopic) displays, which provide a more immersive and interactive experience. By creating depth perception, 3D HUDs enhance situational awareness, improve reaction times, and enable delivery of richer content.
To produce a 3D HUD, the system must create and project two slightly different images – one for each eye – thus mimicking how human eyes perceive depth in the real world. The challenge is to channel each image to the appropriate eye (left image to left eye, and right image to right eye), and to keep these aligned so that they continuously appear to the viewer as a single, 3D image – even as the driver’s eyes change position.
One way this can be accomplished is by using technology that already exists in many vehicles today. It’s the driver monitoring system (DMS), which, amongst other things, tracks driver head and eye movements.
The display is overlaid with an optical element that only allows each eye to see just certain pixels. This can be a parallax barrier, microlens array, lenticular lens, holographic optical element (HOE), or other spatially selective optic. The display is then told to put all the left image information in pixels that are solely visible to the left eye, and vice-versa for the right eye.
However, because the driver’s head isn’t stationary, the set of pixels that are visible exclusively to each eye constantly changes. So, the eye-tracking data from the DMS is used to continuously update the display and shift which pixels contain the left and right eye views. This maintains the proper 3D effect even as the driver shifts position.
A more sophisticated approach that has just recently come into use is the so-called “light field display.” These simultaneously produce many more than just two images (a left and right eye view). They also use some sort of optic to channel each of these views within a narrow angular range.
The result is that, at any viewing position, each eye sees a single, unique view. These views are created so that the left and right eye views always form a “stereo pair” – an image with the proper parallax (depth) information for the viewer to interpret it as 3D. As the viewer’s head shifts, they see different pairs of views – but, again, they are always a pair that the viewer will perceive as 3D.
Light field 3D HUDs typically provide a more natural and continuous 3D viewing experience which can be seen from multiple viewpoints. This enhances realism and reduces any eye strain. However, they are more complex, costly, and can consume more power than 3D HUDs based on pixel shifting.
Seeing More with 3D HUDs: A Glimpse into the Future
The addition of depth perception to the HUD display allows it to present much more data to the driver without it becoming visually overwhelming. In fact, since we are naturally wired to see depth, the information shown in a 3D HUD is actually much easier to understand, and less likely to confuse.
What can be expect in our future 3D HUDs? An obvious possibility is navigational data. This is already incorporated into most 2D HUDs. But, again, the 3D display eliminates any visual ambiguity about exactly “where the arrow is pointing of today.”
LIDAR data can also enhance the functionality of 3D HUDs. For example, it can identify obstacles and highlight dynamic elements, like other cars, people, or animals, likely to cross the vehicle’s path. This real-time information can be projected onto the HUD, providing drivers with critical, situational awareness and allowing for timely, informed reactions to potential hazards.
Data from the web can also be dynamically displayed. For instance, the HUD could be instructed to highlight restaurants as they come into view, indicate parking areas with available spaces, display prices at filling stations, provide dynamic information about EV charging stations, and more.
3D HUDs: Immersive, Informative, Safer
3D Heads-Up Displays will revolutionize the automotive industry by providing an immersive, informative, and safer driving experience. With the integration of cutting-edge photonics, optics, and laser technologies, 3D HUDs are poised to become a standard feature in modern vehicles. As advancements continue and new trends emerge, the future of driving will undoubtedly be shaped by these innovative display systems, making the roads safer and journeys more enjoyable for everyone.
