Retroreflector identification with lidar

A method comprising:

• projecting a plurality of incident beams with an emitter;
• redirecting the plurality of incident beams with a mirror towards an external environment of the emitter;
• rotating the mirror with a motor, thereby adjusting an exit angle of the plurality of incident beams relative to a horizontal axis;
• receiving a plurality of reflected beams with a receiver, where the plurality of incident beams are reflected, as the plurality of reflected beams, by at least one object disposed in the external environment;
• generating an electrical signal with the receiver, where the electrical signal corresponds to a received strength of the plurality of reflected beams;
• receiving the electrical signal from the receiver with a processor;
• generating a histogram with the processor, where the histogram comprises a time-series data plot of the electrical signal such that the histogram depicts the electrical signal as a series of pulses;
• generating a plurality of curves that bound portions of the histogram with the processor, where each curve is associated with a corresponding pulse of the series of pulses;
• determining, for each curve of the plurality of curves, an area value correlating to an area of the histogram delimited by an associated curve of the plurality of curves, thereby producing a plurality of area values, with the processor, that are each associated with the corresponding pulse;
• generating an area table comprising the plurality of area values with the processor;
• classifying each of the plurality of area values that exceeds a retroreflector threshold as retroreflector points with the processor;
• and
• storing the histogram and the retroreflector points with a non-transient storage medium.

A system comprising:

• an optical sensor comprising:
• an emitter configured to project a plurality of incident beams that are reflected, as a plurality of reflected beams, by at least one object disposed in an external environment of the emitter;
• a mirror configured to redirect the plurality of incident beams towards the external environment;
• a motor configured to rotate the mirror, thereby adjusting an exit angle of the plurality of incident beams relative to a horizontal axis;
• and
• a receiver configured to receive the plurality of reflected beams and generate an electrical signal that corresponds to a received strength of the plurality of reflected beams;
• and
• an Electronic Control Unit (ECU) comprising:
• a processor configured to:
• receive the electrical signal from the optical sensor and generate a histogram comprising a time-series data plot of the electrical signal such that the histogram depicts the electrical signal as a series of pulses;
• generate a plurality of curves that bound portions of the histogram, where each curve is associated with a corresponding pulse of the series of pulses;
• determine, for each curve of the plurality of curves, an area value correlating to an area of the histogram delimited by an associated curve of the plurality of curves, thereby producing a plurality of area values each associated with the corresponding pulse;
• generate an area table comprising the plurality of area values;
• and
• classify each of the plurality of area values that exceeds a retroreflector threshold as retroreflector points;
• and
• a non-transient storage medium configured to store the histogram and the retroreflector points.