Correction technology of a polarization lidar with a complex optical system

Abstract

A complex optical system used in polarization lidars often modifies the input polarization of the return signal so that it may significantly impact depolarization estimates and introduce errors to polarization lidar measurements. In most cases, retardation, depolarization, and misalignment of the system exist at the same time and interact with each other. Polarization effects of the system cannot be represented by a simple correction coefficient, so they cannot be removed using a traditional calibration method. Detailed analysis and correction technologies were provided to remove systematic biases in estimating depolarization values from a polarization lidar owing to multiple optical components. The Mueller matrices from an emitter to a receiver were calculated, and the expression for an aerosol depolarization parameter including system polarization effects was derived and obtained. In addition, the correction algorithm based on the Mueller matrix was introduced and provided. A polarization lidar was established, and the polarization characteristics of its optical components were measured with a laboratory ellipsometer; then, the Mueller matrix of the receiver was calculated and obtained. Lidar observations were performed, and our correction algorithm was applied to lidar field data. The results show that the correction method can significantly remove systematic polarization effects.

Scanning polarization lidar LOSA-M3: opportunity for research of crystalline particle orientation in the ice clouds

“…The prism divides the beam into two components with orthogonal polarization, which are further divided along the wavelengths by dichroic beam splitters. Unlike the schemes in which the wavelength division is carried out before separation of polarization components, there is no distortion of the polarization state when reflected from dichroic elements, and there is no need to apply laborious calculations of the instrument vector and correction of the measured polarization (Di et al, 2016).…”

“…The task of observations in lidar networks is to monitor the optical and microphysical properties of aerosol, which requires restoring not only the backscattering coefficient but also the lidar ratio and attenuation. Therefore, a large number of lidars are designed as aerosol-Raman (Althausen et al, 2000;Whiteman et al, 2007;Reichardt et al, 2012;Groß et al, 2015; Haarig et al, 2017;Madonna et al, 2018) or multiwave highspectral-resolution lidars (HSRLs; Eloranta, 2005;Burton et al, 2015). Most of these lidars use dichroic beam splitters as wavelength dividers, and polarizing elements (film po-larizers) are installed after the beam splitters and deflecting mirrors (Nott et al, 2012;McCullough et al, 2018).…”

“…Most of these lidars use dichroic beam splitters as wavelength dividers, and polarizing elements (film po-larizers) are installed after the beam splitters and deflecting mirrors (Nott et al, 2012;McCullough et al, 2018). This leads to distortions in recording polarization components, which require complex procedures for determining the eigenvectors of polarization of the lidar and taking them into account when restoring the polarization state of scattered radiation (Alvarez et al, 2006;Haymann et al, 2012;Freudenthaler et al, 2009;Bravo-Aranda et al, 2016;Di et al, 2016;Freudenthaler, 2016).…”

Depolarization calibration and measurements using the CANDAC Rayleigh–Mie–Raman lidar at Eureka, Canada

“…For the CRL, our approach is to use Mueller matrix mathematics to more fully diagnose the optical properties of CRL's receiver as a whole, similar to the approach taken by Di et al (2016) and Liu and Wang (2013). We do not require the specific contributions of each receiver optic in order to understand our measurements for d. We also do not need to split the matrices into equivalent standard optics (e.g.…”

Low-Level, Liquid-Only and Mixed-Phase Cloud Identification by Polarimetric Lidar

“…These assumptions have been questioned for some optical systems, e.g. (Di et al, 2016), but have been directly measured for CAPABL with a transmitter polarization purity of 123:1 and a receiver polarization purity of > 800 : 1, resulting in an error of the depolarization ratio no greater than 0.8%.…”