New car mirror avoids 'blind spot'

A new car side-view mirror may eliminate the "blind spot" in traffic without distorting the perceived distance of approaching cars, a U.S. journal reports. Research presented in the Optical Society of America's journal Optics Letters describes a design for a mirror that would be free of blind spots, have a wide field of view, and produce images that are accurately scaled to the true size of an approaching object. A curved mirror, such as used on the passenger side of U.S. vehicles, can show more angle of view but make any object seen in it look smaller in size and farther away than it actually is, which is why such mirrors always carry the warning "Objects in mirror are closer than they appear." U.S. and Korean researchers have proposed using a "progressive additive" optics technology commonly used in "no-line multifocal" eyeglasses, where it simultaneously corrects nearsightedness and compensates for reduced focusing ability. The car mirror design would feature a curvature where the inner zone is for distance viewing and the outer zone is for near-field viewing to compensate for what otherwise would be blind spots. "The image of a vehicle approaching from behind would only be reduced in the progressive zone in the center," Hocheol Lee at Hanbat National University in Korea said, "while the image sizes in the inner and outer zones are not changed." Such a design, the researchers said, would offer a greatly expanded field of view, more reliable depth perception and no blind spot.