Investigation of spherical aberration effects on coherent lidar performance

Hu, Qi; Rodrigo, Peter John; Iversen, Theis Faber Quist; Pedersen, Christian

doi:10.1364/oe.21.025670

Cited by 12 publications

(9 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To achieve optimal spatial overlap between the transmit beam and the BPFM, a monostatic lidar geometry is Equation ( 6) has a similar form as the CDL signal-to-noise ratio [18]. Therefore, some important aspects about CDL systems can be adopted for the sFPI-DDL: good optical alignment of the transmit beam and the BPFM is necessary in order to maximize the return signal; analysis of the optimal truncation ratio of a monostatic sFPI-DDL is the same as that of the monostatic CDL [15,16]; optical aberrations in sFPI-DDL should be minimized in order to prevent significant broadening of the spatial confinement [11,29].…”

Section: Experiments and Resultsmentioning

confidence: 99%

“…It is assumed that both transmit and receive beams have Gaussian profiles and are focused by a 50 mm aperture lens without aberration. The normalized targetplane irradiances in Equation ( 6) are calculated numerically by following the approach implemented in [29]. The half width at half maximum Γ of the weighting function is obtained by fitting the result with a Lorentzian function…”

Section: Theorymentioning

confidence: 99%

See 1 more Smart Citation

CW Direct Detection Lidar with a Large Dynamic Range of Wind Speed Sensing in a Remote and Spatially Confined Volume

2021

Self Cite

View full text Add to dashboard Cite

A novel continuous-wave (CW) direct detection lidar (DDL) is demonstrated to be capable of wind speed measurement 40 m away with an update rate of 4 Hz using a fiber-based scanning Fabry–Perot interferometer as an optical frequency discriminator. The proposed CW DDL has a large dynamic wind speed range with no sign ambiguity and its sensitivity is assessed by comparing its performance with that of a CW coherent detection lidar (CDL) in a side-by-side wind measurement. A theoretical model of the spatial weighting function of the fiber-based CW DDL is also presented and validated experimentally. This work shows that the CW DDL has a spatially confined measurement volume with a Lorentzian axial profile similar to that of a CW CDL. The proposed DDL has potential use in various applications in which requirements such as high-speed wind sensing and directional discrimination are not met by state-of-the-art Doppler wind lidar systems.

show abstract

Section: Experiments and Resultsmentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

CW Direct Detection Lidar with a Large Dynamic Range of Wind Speed Sensing in a Remote and Spatially Confined Volume

2021

Self Cite

View full text Add to dashboard Cite

show abstract

“…In a monostatic Doppler lidar with matched LO and transmit beams, "focusing of the beam gives rise to a spatial sensitivity along the beam direction that depends on the inverse of beam area; it follows that the sensitivity rises to a peak at the beam waist and falls symmetrically on either side" [20]. The sensitivity function Q used by Banakh, Smalikho et al [44] is an exact Lorentzian, and (once we make the necessary adjustments in notation) it is the same Lorentzian used by Sonnenschein and Horrigan [2], Frehlich and Kavaya [23], Qi Hu et al [45], and others. We contrasted this with Lindelöw's description of "collection efficiency", which departs from the "1/area" rule.…”

Section: Discussionmentioning

confidence: 99%

Coherent Focused Lidars for Doppler Sensing of Aerosols and Wind

Hill¹

2018

Remote Sensing

View full text Add to dashboard Cite

Many coherent lidars are used today with aerosol targets for detailed studies of e.g., local wind speed and turbulence. Fibre-optic lidars operating near 1.5 µm dominate the wind energy market, with hundreds now installed worldwide. Here, we review some of the beam/target physics for these lidars and discuss practical problems. In a monostatic Doppler lidar with matched local oscillator and transmit beams, focusing of the beam gives rise to a spatial sensitivity along the beam direction that depends on the inverse of beam area; for Gaussian beams, this sensitivity follows a Lorentzian function. At short range, the associated probe volume can be extremely small and contain very few scatterers; we describe predictions and simulations for few-scatterer and multi-scatterer sensing. We review the single-particle mode (SPM) and volume mode (VM) modelling of Frehlich et al. and some numerical modelling of lidar detector time series and statistics. Interesting behaviour may be observed from a modern coherent lidar used at short ranges (e.g., in a wind tunnel) and/or with weak aerosol seeding. We also review some problems (and solutions) for Doppler-sign-insensitive lidars.

show abstract

“…We used the median absolute deviation, MAD (Huber and Ronchetti, 2009;Leys et al, 2013), to distinguish outliers in the bivariate distribution of estimated f and D. MAD can be calculated using…”

Section: Outlier Removalmentioning

confidence: 99%

Methodology for deriving the telescope focus function and its uncertainty for a heterodyne pulsed Doppler lidar

et al. 2020

View full text Add to dashboard Cite

Abstract. Doppler lidars provide two measured parameters, radial velocity and signal-to-noise ratio, from which winds and turbulent properties are routinely derived. Attenuated backscatter, which gives quantitative information on aerosols, clouds, and precipitation in the atmosphere, can be used in conjunction with the winds and turbulent properties to create a sophisticated classification of the state of the atmospheric boundary layer. Calculating attenuated backscatter from the signal-to-noise ratio requires accurate knowledge of the telescope focus function, which is usually unavailable. Inaccurate assumptions of the telescope focus function can significantly deform attenuated backscatter profiles, even if the instrument is focused at infinity. Here, we present a methodology for deriving the telescope focus function using a co-located ceilometer for pulsed heterodyne Doppler lidars. The method was tested with Halo Photonics StreamLine and StreamLine XR Doppler lidars but should also be applicable to other pulsed heterodyne Doppler lidar systems. The method derives two parameters of the telescope focus function, the effective beam diameter and the effective focal length of the telescope. Additionally, the method provides uncertainty estimates for the retrieved attenuated backscatter profile arising from uncertainties in deriving the telescope function, together with standard measurement uncertainties from the signal-to-noise ratio. The method is best suited for locations where the absolute difference in aerosol extinction at the ceilometer and Doppler lidar wavelengths is small.

show abstract

Investigation of spherical aberration effects on coherent lidar performance

Cited by 12 publications

References 10 publications

CW Direct Detection Lidar with a Large Dynamic Range of Wind Speed Sensing in a Remote and Spatially Confined Volume

CW Direct Detection Lidar with a Large Dynamic Range of Wind Speed Sensing in a Remote and Spatially Confined Volume

Coherent Focused Lidars for Doppler Sensing of Aerosols and Wind

Methodology for deriving the telescope focus function and its uncertainty for a heterodyne pulsed Doppler lidar

Contact Info

Product

Resources

About