ANALYSIS: Tomorrow’s rearview mirrors

By Matthew Beecham | 19 June 2012

A wing mirror that eliminates the blind spot for drivers has received a US patent, writes Matthew Beecham. The subtly curved mirror, invented by Drexel University mathematics professor Andrew Hicks, increases the field of view with minimal distortion.     

Traditional flat mirrors on the driver’s side of a vehicle give drivers an accurate sense of the distance of cars behind them but have a very narrow field of view. As a result, there is a region of space behind the car, known as the blind spot, that drivers can’t see via either the side or rearview mirror.

It's not hard to make a curved mirror that gives a wider field of view – no blind spot – but at the cost of visual distortion and making objects appear smaller and farther away.

In explaining where his inspiration came from, Hicks told just-auto: “As a postdoc from 1996-99 in the GRASP Lab at UPenn, under Ruzena Bajcsy, I worked on vision based control systems for robots. Specifically I was supposed to work on robot soccer. An early idea was to mount a spherical mirror above each robot and point the camera up at it. This would give the robot a panoramic view of the scene. I used a ball shaped mirror that I got from Edmund Optics for $20 and it worked pretty well, but the image was very distorted and many pixels in the image were wasted in the sense that the robot saw a big image of itself. I decided to design the mirror so that it saw what I wanted it to see instead.”

Hicks’ driver’s side mirror has a field of view of about 45 degrees, compared to 15 to 17 degrees of view in a flat driver’s side mirror. Unlike in simple curved mirrors that can squash the perceived shape of objects and make straight lines appear curved, in Hicks’ mirror the visual distortions of shapes and straight lines are barely detectable.

Hicks, a professor in Drexel’s College of Arts and Sciences in Philadelphia, US, designed his mirror using a mathematical algorithm that precisely controls the angle of light bouncing off of the curving mirror. “It gives a wide-field of view, given the position of a driver’s eye relative to it, and without the distortion that is common in spherical mirrors that you might see on large vehicles, such as trucks or buses.”

In the US, regulations dictate that cars coming off of the assembly line must have a flat mirror on the driver’s side. Curved mirrors are allowed for cars’ passenger-side mirrors only if they include the phrase “Objects in mirror are closer than they appear.”

Because of these regulations, Hicks’ mirrors will not be installed on new cars sold in the US anytime soon.  The mirror may, however, be manufactured and sold as an aftermarket product that drivers and mechanics can install on cars after purchase. “We’ve had a lot of interest from entities that deal with aftermarket products,” he adds.  Indeed, since being awarded the patent, Hicks says he has received “quite a bit of interest” from other regions of the world.

Some countries in Europe and Asia do allow slightly curved mirrors on new cars. So when could we see it on the road Professor? “Hopefully very soon!”