System and method for speed estimation, detection and ranging using visible light in vehicles

A method for determining the speed of a vehicle, wherein is provided a photodetector, comprising the steps of:

• (a) determining values for K, γ, and d, where,
• K is a constant value that represents a minimum path loss at a reference distance,
• γ is a constant that represents a light power's rate of change as a function of distance, and,
• d is a constant that represents a distance between the vehicle's line of motion and a position of the photodetector;
• (b) reading said photodetector, thereby acquiring a Pr(t) value, where Pr(t) is a power level received from the vehicle at a time t;
• (c) performing step (b) a plurality of times, thereby acquiring a plurality of different Pr(t) values at a plurality of different time values;
• (d) using at least said determined values for K, γ, and d, and said plurality of Pr(t) values to obtain an estimate of said speed of said vehicle by solving the equation:
• (
• P
• r
• ⁡
• (
• t
• )
• K
• )
• -
• 2
• ⁢
• ⁢
• d
• 2
• =
• Vt
• +
• R
• o
• ,
• for V and R0, where
• V is an estimate of said speed of said vehicle, and,
• R0 is an initial range between the vehicle and said photodetector;
• and
• (e) displaying said speed estimate to a user using a display device in electronic communication with said photodetector.

An apparatus for determining the speed of a vehicle, comprising,

• (a) a photodetector, said photodetector at least for emitting a signal representative of a light power received thereby;
• (b) a CPU in electronic communication with said photodetector, said CPU at least for reading a signal from said photodetector;
• (c) a display device in electronic communication with said CPU;
• (d) computer memory in communication with said CPU, said computer memory containing a plurality of commands for executing at least the following steps
• (1) determining values for K, γ, and d, where,
• K is a constant value that represents a minimum path loss at a reference distance,
• γ is a constant that represents a light power's rate of change as a function of distance, and,
• d is a constant that represents a distance between the vehicle's line of motion and a position of the photodetector;
• (2) reading said photodetector, thereby acquiring a Pr(t) value, where Pr(t) is a power level received from the vehicle at a time t;
• (3) performing step (2) a plurality of times, thereby acquiring a plurality of different Pr(t) values at a plurality of different time values;
• (4) using at least said determined values for K, γ, and d, and said plurality of Pr(t) values to obtain an estimate of said speed of said vehicle by solving the equation:
• (
• P
• r
• ⁡
• (
• t
• )
• K
• )
• -
• 2
• ⁢
• d
• 2
• =
• Vt
• +
• R
• o
• ,
• for V and R0, where
• V is an estimate of said speed of said vehicle, and,
• R0 is an initial range between the vehicle and said photodetector;
• (5) displaying said speed estimate to a user using said display device.