A License Plate Recognition and Speed Detection System - Index of

We briefly considered laser rangefinders, but decided they were too dangerous and
costly, even if we could obtain ones that were used by law enforcement. A special class of laser
is required for police laser radar detectors, which adds to their cost. The laser rangefinders used
for measuring distance on a golf course, for example, are not manufactured in a way that allows
them to be pointed at people. Thus, they would be extremely dangerous if used to measure
vehicle speeds. We would also have the problem of measuring the speed of an object since these
units are for distance only.
The traffic classifier units and traffic counters with road tubes, while less expensive than
the speed trailers and police radar units, have the major drawback of needing to place a portion
of the unit in the roadway. We felt that this would require special permission from the various
regulatory agencies (State Department of Transportation, State Traffic Commission, City of New
Britain, etc.) which may have taken a long time to be granted, if at all.
Both the PIR motion detectors and the ultrasonic rangefinder, while inexpensive,
have problems with the wide detection field and short effective distance. The camera system we
decided to use provides a quality image at distances from 50 to 500 feet, depending on which
camera lens is installed. Although the PIR detector could cover the shorter end of this range, it
would respond to any motion within a 60-degree field of view. The ultrasonic detector suffered
from an extremely short usable range, which did not exceed 10 feet.
This leaves us with the microwave radar units, of which we found two very inexpensive
types. Mattel Toys makes one for their Hot Wheels 1/64 in. scale cars (fig. 15), and the other one
is a kit made by Ramsey Electronics (fig. 16).
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