Laser ceilometer signal processing means

In a pulsed-laser lidar, comprising a pulsed laser source for projecting toward a target a pulsed laser beam through a turbid medium bearing a distribution of suspended particles;

• radiation collector means for gathering target return radiation scattered from the pulsed laser beam by the target, superimposed upon background return radiation scattered from the pulsed laser beam by the distribution of suspended particles;
• electro-optical detector means for receiving said superimposed return radiations gathered by said collector means and transducing said superimposed return radiations to a corresponding electrical signal pulse waveform comprising a target signal pulse, from received and transduced target return radiation, superimposed upon a background signal waveform, from received and transduced background return radiation;
• and
• output means for receiving and presenting said electrical signal pulse waveform as a measure of at least one target attribute such as presence, range or magnitude, the improvement comprising:
• electrical signal processing means, intermediate said electro-optical detector means and said output means, said electrical signal processing means applying, to said electrical signal pulse waveform, a time-distributed signed electrical weighting function having negligible total weight within a total time interval which can contain said electrical signal pulse waveform and said time-distributed signed electrical weighting function having alternations of sign separated by time intervals of the order of the width of said target signal pulse.