Correlation based optical ranging and proximity detector

A method of detecting and ranging objects from a source location comprising steps of:

• transmitting a transmission signal from a ranging detector at said source location, including modulating said transmission signal in accordance to a binary code having an autocorrelation function with negative sidelobes;
• subsequent to said step of transmitting said transmission signal, receiving a return signal by said ranging detector at said source location;
• cross-correlating said return signal with a first correlation signal and a second correlation signal to produce a first autocorrelation signal and a second autocorrelation signal, said first and second correlation signals being time-delayed versions of said binary code, said second correlation signal being further time-delayed than said first correlation signal by a preselected bit period;
• combining said first and second autocorrelation signals in a manner at least partially based on a signal summing to derive a summed signal;
• combining said first and second autocorrelation signals in a manner at least partially based on a signal differencing to derive a difference signal;
• and
• processing said summed and difference signals by a processor of said ranging detector to determine presence of a target, said presence being defined by relative amplitudes of said summed and difference signals.

A system for detecting presence of objects at a vicinity from a source location comprising:

• a code sequence generator configured to generate a binary code having an autocorrelation function with negative sidelobes;
• a transmitter electrically coupled to said code sequence generator to emit an electromagnetic signal that is representative of said binary code;
• a receiver operatively associated with said transmitter to receive a return electromagnetic signal;
• a first correlator connected to said receiver and said code sequence generator designed to compare said return signals with a first correlation code to produce a first autocorrelation signal, said first correlation code being said binary code with a selected time delay, said selected time delay defining a predetermined proximity from said source location being monitored;
• a second correlator connected to said receiver and said code sequence generator designed to compare said return signal with a second correlation code to produce a second autocorrelation signal, said second correlation code being said first correlation code with a one-bit period delay;
• calculating means electrically coupled to said first and second correlators for summing and subtracting said first and second autocorrelation signals in order to output a sum signal and a difference signal;
• and
• a processor connected to said calculating means to analyze said sum and difference signals, said processor configured to determine whether said return signal is an echo of said emitted electromagnetic signal from a target at said predetermined proximity by the analysis of said sum and difference signals.