Detection of an obscurant on an environment surface by a lidar system

A method, comprising:

• emitting an output beam comprising pulses of light through a window;
• scanning the output beam across a field of regard of the system;
• detecting, through the window, received pulses of light corresponding to scattered reflection returns of a first part of the emitted pulses of light, wherein scattered reflection returns, if any, of a second part of the emitted pulses of light are below a detection threshold of the receiver;
• and
• determining whether at least a portion of the second part of the emitted pulses of light corresponds to an obscurant on an environment surface including by:
• receiving a new point cloud including a group of points corresponding to the environment surface;
• clustering at least a portion of the group of points to form a projected shape approximating at least a portion of the environment surface;
• clustering into an obscurant candidate cluster at least a portion of the second part of the emitted pulses of light that belong to projected locations within the projected shape;
• comparing the obscurant candidate cluster with a previously determined obscurant candidate cluster of a previous point cloud to determine whether a detected change from the comparison conforms to a detected physical movement of the system;
• and
• in response to a determination that the detected change from the comparison conforms to the detected physical movement of the system, classifying the obscurant candidate cluster as the obscurant on the environment surface.

A computer program product embodied in a non-transitory computer readable medium and comprising computer instructions for:

• emitting an output beam comprising pulses of light through a window;
• scanning the output beam across a field of regard of the system;
• detecting, through the window, received pulses of light corresponding to scattered reflection returns of a first part of the emitted pulses of light, wherein scattered reflection returns, if any, of a second part of the emitted pulses of light are below a detection threshold of the receiver;
• and
• determining whether at least a portion of the second part of the emitted pulses of light corresponds to an obscurant on an environment surface including by:
• receiving a new point cloud including a group of points corresponding to the environment surface;
• clustering at least a portion of the group of points to form a projected shape approximating at least a portion of the environment surface;
• clustering into an obscurant candidate cluster at least a portion of the second part of the emitted pulses of light that belong to projected locations within the projected shape;
• comparing the obscurant candidate cluster with a previously determined obscurant candidate cluster of a previous point cloud to determine whether a detected change from the comparison conforms to a detected physical movement of the system;
• and
• in response to a determination that the detected change from the comparison conforms to the detected physical movement of the system, classifying the obscurant candidate cluster as the obscurant on the environment surface.