Method and apparatus for detecting an object on a side of or backwards of a vehicle

A system for detecting an external obstacle within a given distance and spatial location on a side of or to the rear of a vehicle comprising:

• a rangefinder mounted on said vehicle for determining distance to an external obstacle within said spatial location including:
• a transmitter of pulses of electromagnetic light radiation having a narrow beam width and a given pulse frequency transmitted within said spatial location;
• a receiver that receives reflected light radiation pulses transmitted from the transmitter and reflected by said obstacle;
• a timing device determining the time interval between pulses transmitted by said transmitter and reflected pulses from said obstacle received by said receiver where the time interval is less than approximately 200 nanoseconds and is a measure of the distance to said obstacle, said timing device including a digital clock producing clock pulses and a clock pulse counter activated to count clock pulses upon initiation of transmitter pulses and stopped upon receipt of reflected pulses by said receiver, said clock pulses being a measure of said time interval and said time interval between said transmitted and received pulses being a measure of distance to said obstacle;
• a data averager connected to said clock pulse counter for maintaining a running average of time interval information of a plurality of successive transmitted and received pulses;
• and
• means for determining from said time interval information if the distance to said obstacle falls within a preset range between a lower distance bound and an upper distance bound, said means for determining distance within a preset range including a range gate discriminator receiving time interval information from said data averager;
• control means for controlling the operation of said rangefinder and providing an output from said rangefinder upon occurrence of reflected pulses within said range;
• and
• a display receiving said output and displaying the results of the distance determination to the operator of the vehicle.