Analytical function for lidar geometrical compression form-factor calculations

Stelmaszczyk, K.; Dell’Aglio, M.; Chudzyński, S.; Stacewicz, T.; Wöste, L.

doi:10.1364/ao.44.001323

Cited by 72 publications

(53 citation statements)

References 18 publications

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“…1a), with the constraint that A tilt ≤ RFOV − LBD, allows a decrease of the RFOV with constant DFO or a decrease of the DFO with constant RFOV (Stelmaszczyk et al, 2005). The optimum A tilt is either the one that minimizes the RFOV or the DFO respectively, and for both aforementioned cases becomes equal to…”

Section: Description Through Paraxial Approximationmentioning

confidence: 99%

“…There are several studies in the literature related to the determination of the overlap function of lidar systems analytically (e.g., Halldórsson and Langerholc, 1978;Jenness et al, 1997;Chourdakis et al, 2002;Stelmaszczyk et al, 2005;Comeron et al, 2011) or experimentally (e.g., Sasano et al, 1979;Tomine et al, 1989;Dho et al, 1997;GuerreroRascado et al, 2010;Wandinger and Ansmann, 2002). For the theoretical approaches, a good understanding of the actual light distribution in the laser beam cross section, and the characteristics of the receiving unit are needed to obtain an overlap profile with sufficient accuracy.…”

Section: Introductionmentioning

confidence: 99%

“…For the theoretical approaches, a good understanding of the actual light distribution in the laser beam cross section, and the characteristics of the receiving unit are needed to obtain an overlap profile with sufficient accuracy. Stelmaszczyk et al (2005) also proposed an analytical formula to decrease the DFO based only on the laser telescope geometry and specifically the introduction of a small inclination between the transmitter and receiver central axis. However, all the aforementioned theoretical studies provide information regarding the overlap function based explicitly on the laser telescope setup.…”

Section: Introductionmentioning

confidence: 99%

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Using paraxial approximation to describe the optical setup of a typical EARLINET lidar system

Kokkalis

2017

Atmos. Meas. Tech.

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Abstract. The mathematical formulation for the optical setup of a typical EARLINET lidar system is given here. The equations describing a lidar system from the emitted laser beam to the projection of the telescope aperture on the final receiving unit (i.e., photomultiplier or photodiode) are presented, based on paraxial approximation and geometric optics approach. The receiving optical setup includes a telescope, a collimating lens, an interference filter and the ensemble objective eyepiece. The set of the derived equations interconnects major parameters of the optical components (e.g., focal lengths, diameters, angles of incidence), revealing their association with the distance of full overlap of the system. These equations may used complementarily with an optical design software, for the preliminary design of a system or can be used as a quick check up tool of an existing lidar system. The evaluation of the formulation on a real system is performed with ray-tracing simulations, revealing an overall good performance with relative differences of the order of 5 % mainly attributed to the limitations of the thin lens approximation.

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Section: Description Through Paraxial Approximationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Using paraxial approximation to describe the optical setup of a typical EARLINET lidar system

Kokkalis

2017

Atmos. Meas. Tech.

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“…The overlap function can theoretically be modelled if the specifications and configuration of the optical elements of the lidar are known (Kuze et al, 1998;Stelmaszczyk et al, 2005). In practice, due to several unknown instrumental efPublished by Copernicus Publications on behalf of the European Geosciences Union.…”

Section: Introductionmentioning

confidence: 99%

An empirical method to correct for temperature-dependent variations in the overlap function of CHM15k ceilometers

2016

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Abstract. Imperfections in a lidar's overlap function lead to artefacts in the background, range and overlap-corrected lidar signals. These artefacts can erroneously be interpreted as an aerosol gradient or, in extreme cases, as a cloud base leading to false cloud detection. A correct specification of the overlap function is hence crucial in the use of automatic elastic lidars (ceilometers) for the detection of the planetary boundary layer or of low cloud.In this study, an algorithm is presented to correct such artefacts. It is based on the assumption of a homogeneous boundary layer and a correct specification of the overlap function down to a minimum range, which must be situated within the boundary layer. The strength of the algorithm lies in a sophisticated quality-check scheme which allows the reliable identification of favourable atmospheric conditions. The algorithm was applied to 2 years of data from a CHM15k ceilometer from the company Lufft. Backscatter signals corrected for background, range and overlap were compared using the overlap function provided by the manufacturer and the one corrected with the presented algorithm. Differences between corrected and uncorrected signals reached up to 45 % in the first 300 m above ground.The amplitude of the correction turned out to be temperature dependent and was larger for higher temperatures. A linear model of the correction as a function of the instrument's internal temperature was derived from the experimental data. Case studies and a statistical analysis of the strongest gradient derived from corrected signals reveal that the temperature model is capable of a high-quality correction of overlap artefacts, in particular those due to diurnal variations. The presented correction method has the potential to significantly improve the detection of the boundary layer with gradientbased methods because it removes false candidates and hence simplifies the attribution of the detected gradients to the planetary boundary layer. A particularly significant benefit can be expected for the detection of shallow stable layers typical of night-time situations.The algorithm is completely automatic and does not require any on-site intervention but requires the definition of an adequate instrument-specific configuration. It is therefore suited for use in large ceilometer networks.

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“…Geometrical optics has been employed analytically [12][13][14][15][16], through ray tracing [17,18], and in a hybrid approach along with diffraction theory [19]. These theoretical techniques are extremely useful for lidar system design; however, the success of these approaches for overlap calibration of a specific instrument in the field relies on reliable knowledge of system parameters.…”

Section: Introductionmentioning

confidence: 99%

Determination of overlap in lidar systems

Hey

Coupland

Foo³

et al. 2011

Appl. Opt.

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The overlap profile, also known as crossover function or geometric form factor, is often a source of uncertainty for lidar measurements. This paper describes a method for measuring the overlap by presenting the lidar with a virtual cloud through the use of an imaging system. Results show good agreement with horizontal hard target lidar measurements and with geometric overlap calculated for the ideal aberration-free case.

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Analytical function for lidar geometrical compression form-factor calculations

Cited by 72 publications

References 18 publications

Using paraxial approximation to describe the optical setup of a typical EARLINET lidar system

Using paraxial approximation to describe the optical setup of a typical EARLINET lidar system

An empirical method to correct for temperature-dependent variations in the overlap function of CHM15k ceilometers

Determination of overlap in lidar systems

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