Intensity-modulated, stepped frequency cw lidar for distributed aerosol and hard target measurements

Abstract

A compact frequency-modulated, continuous wave (FM-cw) lidar system for measurement of distributed aerosol plumes and hard targets is presented. The system is based on intensity modulation of a laser diode and quadrature detection of the return signals. The advantages of using laser diode amplitude modulation and quadrature detection is a large reduction in the hardware required for processing and storing return signals as well as the availability of off-the-shelf integrated electronic components from the wireless and telecommunication communities. Equations to invert the quadrature signal components and determine spatial distributions of multiple targets are derived. Spatial scattering intensities are used to extract aerosol backscatter coefficients, which can then be directly compared to microphysics aerosol models for environmental measurements. Finally, results from laboratory measurements with a monostatic FM-cw lidar system with both hard targets and aerosols are discussed.

Monitoring Automotive Particulate Matter Emissions with LiDAR: A Review

“…For this application, a LiDAR approach needs to be employed to properly account for the variable spatial distribution and location of the vehicle plume and for the range-dependence of the backscattered signal. An interesting development, based on intensity-modulated, stepped frequency CW LiDAR, was proposed by Simpson et al [50]. The system, based on CW laser diode operating at 660 nm, showed potential for its low cost and simplicity; however, to our knowledge, data and analysis from the operational on-road deployment of the system are not currently publicly available.…”

Application of lidar techniques to time-of-flight range imaging

“…Intensity modulated SFCW lidar has been employed by Simpson et al [25] for resolving multiple translucent sheets, and we show that SFCW can be applied to ToF range cameras for full field video frame rate range cameras. Standard lidar processing algorithms are applied to estimate the velocity of moving objects and the distance of stationary objects.…”

“…A slight modification to FMCW is stepped frequency continuous wave (SFCW) radar, In which a single frequency is emitted at a time, with an increase in frequency for each step. SFCW is common in ground penetrating radar where the signal to noise ratio (SNR) is important and there are more relaxed measurement times [24], and SFCW has been demonstrated in lidar by Simpson et al [25]. The relationship between the modalities from radar that we consider for ToF are illustrated in Fig.…”

Fourier Analysis on Transient Imaging with a Multifrequency Time-of-Flight Camera

“…In remote sensing, Simpson et al [23] introduce an Amplitude Modulated Continuous Wave (AM-CW) technique with discrete stepped frequency in Lidar system and use inverse Fourier transform to recover the scattering function of the environment across time. In fluorescence lifetime imaging microscopy (FLIM) [24], timeresolved fluorescence light can be captured and reconstructed by either time domain techniques [25] or frequencydomain techniques [26].…”