Optical highway line detector

A detector for detecting light reflected from lines on a highway surface from a moving motor vehicle, comprising:

• a photodetector mounted to receive light reflected from the lines in a predetermined manner when the vehicle is properly within a lane but not otherwise;
• an alarm to, once enabled, provide an indication when light is received by the photodetector in other than the predetermined manner;
• and
• a dynamic impedance element electrically connected in series with the photodetector to maintain the photodetector in condition to detect light reflected from a line regardless of ambient illumination of the highway and line.

A detector for detecting light reflected from discontinuous lane dividing lines on a highway surface from a moving motor vehicle, comprising:

• a photodetector mounted to receive light reflected from the discontinuous lane dividing lines when the vehicle is properly within a lane but not otherwise;
• circuitry to produce a pulse for each lane dividing line sensed;
• logic circuitry to determine if a pulse is produced, indicating a line sensed within successive fixed periods of time in which it is expected that a line should be sensed;
• and
• an alarm to, once enabled, provide an alarm indication if the logic circuitry determines an alarm condition exists.

A method for detecting whether a vehicle is maintaining position in a highway lane marked by at least one set of discontinuous lane dividing lines on the highway surface, comprising the steps of:

• detecting, using a photodetector, discontinuous lane dividing lines marking the lane in which the vehicle is traveling;
• determining through logic circuitry if a line is detected in each of a succession of time periods in which it would be expected lines would be detected if the vehicle stayed in the lane and detected such lines;
• and
• giving an alarm if such lines are not detected in each of the expected successive time periods, such lines not being detected indicating the lines are not being sensed and possible drift of the vehicle out of the lane.