Importance

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Abstract

A highway line detection system which is insensitive to changes in road surface warns the driver of a motor vehicle when the vehicle is about to drift across either a center line or an edge line. A unit on each side of the vehicle directs light rays rich in infrared and red radiation downwardly toward the road surface, and includes a photoresponsive receiver responsive to the rays reflected from a painted line or mark. A valid center line or edge line has a width within a predetermined range of minimum and maximum widths and is recognized by the receiver to activate a suitable alarm, but other markings of greater or lesser width are discriminated against to prevent a false alarm. The receiver employs a series of photoconductive cells which are highly sensitive to radiation in the red and near infrared region; they are spaced horizontally on a line extending orthogonally with respect to the fore-and-aft axis of the vehicle in order to establish corresponding spaced points at which reflected rays are detected. Logic circuitry responsive to the photocell outputs activates the alarm if the combination of responding photocells is indicative of the reflection of received rays from a line on the road surface of at least said minimum width but no greater than said maximum width.

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First Claim