Optical sensor for odometry tracking to determine trajectory of a wheel

An optical sensor system mounted in a wheel arch in a car for counting an outer surface of a wheel covered with evenly-spaced wheel treads to determine trajectory of the wheel, the optical sensor system comprising:

• a first optical sensor mounted in the wheel arch above the wheel for performing a plurality of counts corresponding to respectively capturing a plurality of images of the wheel according to the wheel treads;
• a first clear casing mounted in the wheel arch between the wheel and the first optical sensor, but not touching the wheel;
• a second optical sensor mounted in the wheel arch on one side of the wheel for performing a plurality of counts corresponding to respectively capturing a plurality of images of the wheel according to the wheel treads;
• a second clear casing mounted in the wheel arch between the wheel and the second optical sensor, but not touching the wheel;
• a third optical sensor mounted in the wheel arch on the other side of the wheel for performing a plurality of counts corresponding to respectively capturing a plurality of images of the wheel according to the wheel treads;
• and
• a third clear casing mounted in the wheel arch between the wheel and the third optical sensor, but not touching the wheel;
• wherein the captured images are compared with a reference image to determine a 2D displacement, a calculation is performed to convert the measured 2D displacement of the wheel from its original position into a distance the wheel travels along a path in order to determine the wheel trajectory, the wheel trajectory is determined by calculating a turning degree of the wheel according to a trigonometric manipulation of the captured 2D displacement, the calculated turning degree and at least a distance between a front wheel axle and a rear wheel axle of the car are utilized to determine a turning curve along which the wheel moves, the turning curve being centered on a point where an extended line from the rear axle crosses a perpendicular line to the front axle.