Speckle effects on time-of-flight estimation of lidar pulses

Speckle effects particularly impact the performance of compact lidars. The surface roughness and slope spread a received laser pulse to contain M temporal speckle cells, distorting the pulse shape and degrading the centroid-based time-of-flight (ToF) estimation. Laser spectral broadening from repeated phase modulation increases M and improves the ToF estimation when the surface is significantly rough, but degrades the ToF estimation moderately when the surface is smoother. The solar background and dark noise contributions can be reduced by weighting the waveforms. Line-fitting and plane-fitting to multiple return waveforms are analyzed for precision retrievals of the range rate, slope, and range.