| 摘要 |
The proximity of a boundary of a roadway is detected optically by apparatus mounted to a vehicle (12). The apparatus includes an array of light sensitive elements (11) to receive light reflected from a transverse strip of the roadway. The output values of the light sensitive elements (11) are analysed by a microprocessor to detect substantial differences between neighbouring elements, indicative of the contrasting bright and dark portions on either side of the boundary, which may be a road edge or white line (13). The exposure time for the light sensitive elements is adjusted automatically, based on the minimum actual brightness level detected. The microprocessor is able to identify a white line by scanning the output values from the array of light sensitive elements to detect differences corresponding to a dark-to-bright transition and a bright-to-dark transition. If the distance between these transitions is within a predetermined range, the microprocessor identifies the feature as a line. A light shield (14) is mounted around the array of light sensitive elements, to minimise the effect of stray light.
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