Picosecond pulsewidth direct detection lidar for imaging applications

摘要

In this paper, the development of a novel picosecond pulsewidth direct detection lidar for velocimetry and hardtarget imaging applications is discussed. The lidar system comprises of a high-speed fiber coupled laser, novelinterleaved three-dimensional (3D) scanner, fiber coupled receiver with optical pre-amp module and a high-speeddigitizer. The laser is a pulsed Erbium-doped fiber laser that operates at 1.55 microns wavelength, 10 MHz PRF, 60picosecond pulse width and 8 W of output average power. The scanner is a multi-faceted polygon type that operatesat scan speeds of 10000 lines per second. The system utilizes a state-of-the art 40 GS/s digitizer. The picosecondlidar allows high resolution volumetric measurement of temporally and spatially resolved 3D airspeeds in windtunnels for capturing a 3D time-accurate map of aerosols or other seeding particles in the airflow using elasticbackscatter from a rapidly scanned lidar beam with a narrow field-of-view. Preliminary testing inside wind tunnelhas generated promising results for aerodynamic applications including visualizing flow characteristics around testtargets. The lidar provided dynamic measurements of complex flow, including the downstream evolution of a wingtip vortex. A 3D image processing algorithm was used to correlate the motion of aerosol features between successiveframes and to extract 3D airflow profiles. In this paper, details of lidar instrumentation configuration is discussedfollowed by results of high-speed 3D hard target imaging of various test targets.