When it comes to the much-talked-about lack of a rear window in the new Polestar 4, you’ll soon find that the digital rearview mirror the Swedish battery-electric-vehicle maker opted for as a substitute is more than a tech novelty.
The Polestar 4, already available overseas but arriving this fall for North America, has a sleek “SUV coupe” form – frameless doors, a more aerodynamic silhouette...and yes, no rear window. The form was accomplished by Polestar engineers shifting the structural header at the back of the roof to a spot well behind passengers’ heads instead of directly over or ahead of them. The lack of much rear glass and the structural configuration gives the SUV something more akin to a trunk lid than a liftgate.
The technology behind the vehicle’s rearview mirror camera substitute isn’t entirely new but has a new twist. It’s an evolution of what racecars and cargo vans have relied on for many years – and what its supplier, Michigan-based Gentex, originally launched in 2015 for the 2016 model year. Gentex says its digital rearview mirror camera-based system now is offered in over 130 different vehicles from more than 30 different brands.
But the Polestar 4’s system takes the notion of digital eyes a step further: It will be the first American mass-market passenger vehicle not to have a traditional mirror to flip back to. In most of today’s vehicles with the Gentex digital rearview system, a user can opt out, so to speak, by flipping a tab to turn the camera view off and return to a mirror view.
The progression in the technology comes as the screen mounted within the Polestar 4’s unit has a 1480x320 resolution, cropped from a 1920x1280 resolution, on an 8.9-in. (23-cm) display, while the 2.5-megapixel camera enables a 121-degree field of vision – far greater than what you might be able to crane your neck around to with a traditional rearview mirror setup.
The unit in the Polestar 4 has Gentex’s second-generation version of its digital rearview mirror camera system, with the new camera unit plus custom image signal processing able to purge LED headlight flicker, cut glare and sharpen the view in all weather and lighting conditions.
Gentex’s camera used in the Polestar 4 has a water-repellent coating, as well as an antireflective one, and the supplier says a unit with an OLED screen and additional water-shedding tech is in development.
Better Eyes, But it Puts Eyes to the Test
How well does it all work? After driving one of the first North American-spec Polestar 4s in July in an afternoon thunderstorm and downpour, WardsAuto finds visibility with the camera system is far better than it might be through a rear window in such a situation.
The team behind the Polestar 4 admits that adapting to the rearview display may be one of the biggest initial hurdles for drivers. If a person sometimes needs reading glasses, shifting the field of focus to the rather close mirror can be disorienting at first, although, after about an hour, we mostly adapted to the setup.
According to Gentex, research shows that 82% of users acclimate to using a digital display within a few days or less, while 94% acclimate to it within a few weeks of driving.
Its Own Camera, Leaving Safety Systems Be
As Polestar’s product lead Christian Samson underscores, the strategy to use a camera instead of have a rear window with a traditional rearview mirror doesn’t cut costs or materials, as the car’s design takes hatch glass and essentially shifts it to the roof – which in top-spec versions can cloud or clear electrochromatically. But it gives the Polestar 4 a better combination of attributes than other such SUV coupes to give it a competitive edge, the brand contends. The vehicle has up to 300 miles (483 km) of range on the EPA test cycle from 94 kWh of usable battery capacity.
To capture the back field of view, two rear-facing cameras are mounted atop the roof, near the rear, with one of those dedicated to the rearview display. “We wanted this stream to be an independent stream, not impacted or conflicting or disturbed by more control units handling the images in different ways,” explains Ola Aldensjö, the product manager for Polestar 4, who describes the system as “fairly disconnected from the rest of the electrical architecture.”
Next to all the cameras and active-safety systems already installed within the Polestar 4, the two rearview side mirrors on the Polestar 4 seem like vestiges of the past. With digital side mirrors not yet legal in the U.S., that future is coming into view for Americans much more slowly.
