Good drivers do not put their faith in wing mirrors – the only safe way to overtake is to take a quick glance over one’s shoulder to check for vehicles approaching from behind – but an optical prescription for car wing mirrors could eliminate dangerous blind spots without distorting the perceived distance of other cars.
According to a paper published this week in the Optical Society journal Optics Letters, objects viewed in the new design of mirror appear larger making it easier easier to judge their distance and speed.
According to the Optics Society:
Today’s motor vehicles in the United States use two different types of mirrors for the driver and passenger sides. The driver’s side mirror is flat so that objects viewed in it are undistorted and not optically reduced in size, allowing the operator to accurately judge an approaching-from-behind vehicle’s separation distance and speed. Unfortunately, the optics of a flat mirror also create a blind spot, an area of limited vision around a vehicle that often leads to collisions during merges, lane changes, or turns. The passenger side mirror, on the other hand, possesses a spherical convex shape. While the small radius of curvature widens the field of view, it also causes any object seen in it to look smaller in size and farther away than it actually is. Because of this issue, passenger side mirrors on cars and trucks in the United States must be engraved with the safety warning, “Objects in mirror are closer than they appear.” In the European Union, both driver and passenger side mirrors are aspheric (One that bulges more to one side than the other, creating two zones on the same mirror).The inner zone—the section nearest the door—has a nearly perfect spherical shape, while the outer zone— the section farthest from the door—becomes less and less curved toward the edges. The outer zone of this aspheric design also produces a similar distance and size distortion seen in spherical convex designs.
Researchers at Hanbat National University in Korea and Portland State University in Oregon believe they have solved the problem by turning to the technology used in no-line multi-focal spectacles to produce a wing mirror with three zones: one for distance vision, one for close-up viewing and a middle zone making the transition between the two.
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