Electronics and Semiconductors

Fundamentals of laser HUDs for automotive

23 September 2021
Existing HUD technology is being improved to display brighter, clearer images that use AR to integrate into the real world. Source: AdobeStock

Head up displays (HUDs) were first created for defense aviation purposes many years ago. As with all technology these days, it is rapidly improving and being adapted to automobiles to present drivers with certain information like navigational and speed data. This is displayed on a see-through screen that is not intended to block the driver’s sight or distract the driver in any way.

This is one of the most important aspects of HUDs — to not distract the driver but to also be a useful resource for them while driving. Market research from BCC Research found that the HUD market is projected to increase from $2.7 billion to $8 billion in the next year. The two options below are what original equipment manufacturers (OEM) are using as their cutting-edge technology to create these new HUDs and improve the driving experience for everyone.

Laser-scanned MEMS displays

Within a laser-scanned microelectromechanical systems (MEMS) projector, every pixel is pulsed very quickly to generate full high definition (HD) resolution. The laser beam is constantly in focus, which means that the image it is displaying can be projected onto the windscreen without the need for any refocusing apparatus. This naturally reduces the complexity, cost, and size of the system, as many expensive optical parts and assemblies are not required.

Laser-scanned MEMS HUDs use electrical power when there are pixels that need to be projected. With the usual instrumentation and navigation information that they are required to display, projecting the necessary pixels onto the display is what uses the most energy. This method uses much less electrical energy than its predecessors, giving the system a decreased thermal profile and therefore reducing the need to remove heat from the assembly.

Laser diode drivers, for example the ISL8365 from Intersil, pulse a number of lasers (in this case four) up to 750 mA to project full HD video onto a windshield. These chips can work with a vast array of color laser diode setups, this gives HUD designers more flexibility to create a product that still has the required contrast, rich color, and brightness. To meet the thermal demands, there are three power-saving modes offered by the devices for low power loss and high efficiency.

DLP technology

DLP is a technology that is based on optical MEMS for display devices. Essentially, it is a digital micromirror device. Texas Instruments have adapted the technology behind their existing DLP Cinema projection system for use on automotive applications. This assembly includes digitally switchable, highly reflective, micrometer-sized mirrors (also known as micromirrors). This array of mirrors has 608 micromirror columns and 684 micromirror rows arrange in a diamond pixel configuration. Every micromirror is placed over a CMOS memory cell. The binary state of the CMOS memory cell after the mirror docking pulse determines the angular position of each micromirror.

The Texas Instruments chipsets target augmented-reality HUD and a wide field of view reaching 12 by 5 deg. This particular chipset’s (DLP3000-Q1) family includes a digital micromirror device (DMD), a DLPC12 controller and a DLP 0.3 inch wide video graphics array (WVGA). The controller is tasked with receiving the video input and converting the data in order to be displayed on the DMD, while also controlling the RGB light emitting diodes (LEDs) to generate an image in real-time. The controller also powers up and shuts down the DMD under direction from the temperature input or external system control from the DMD.

In cars by 2024?

An automotive AR HUD was unveiled recently that uses artificial intelligence (AI), similar to what Tesla has been using to develop their driver assistance systems like self-driving. This system shows the road ahead for navigation, but it also can inform the driver of other vehicles, foreign objects on the road, cyclists and pedestrians. It can even detect heights of underpasses, which will be essential information for those driving trucks or hauling tall trailers. Each feature is separately labeled in order to give the driver to best driving experience possible.

The HUD also has eye tracking, which ensures that the projected information will be in the perfect position at all times for the driver, no matter what direction they are looking in. It can adjust the display in under 300 milliseconds. This new technology will have to perform at an extremely high level of accuracy, in order to correctly show a path on the road, lane marking and arrows for where to turn. It will also have to deal with vibration and bumpy roads, which Panasonic (the manufacturer) assures it can deal with seamlessly and will stay locked on to the driver.

A system like this obviously uses advanced optical technology, and sensors will be used to identify objects at 33 feet and further even at night or in low light. 3D imaging radar will also help to capture a 180° view of the world for 300 feet in front of the vehicle. Holographic and laser technology will make 4k resolution projections possible on the vehicle’s windscreen. Panasonic say this HUD system will be integrated into vehicles in 2024 but neglected to mention which automotive manufacturer that they are working with.

Hyundai and Porsche have invested $80 million into WayRay, which is also promising a vibrant, immersive and…interactive HUD!? The specs for their particular HUD are similar to what Panasonic is offering, but what is more interesting is their plan to eventually make the entire windshield an AR immersive experience, but that is quite far down the road at this stage.

Do you think laser HUDs will become a staple in all new cars? Will it be like having real-life navigation showing you where to go on the road in front of you? Engineering360 would love to hear your thoughts!

To contact the author of this article, email engineering360editors@globalspec.com

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