Depolarizing metrics for plant samples imaging

Abstract

Optical methods, as fluorescence microscopy or hyperspectral imaging, are commonly used for plants visualization and characterization. Another powerful collection of optical techniques is the so-called polarimetry, widely used to enhance image contrast in multiple applications. In the botanical applications framework, in spite of some works have already highlighted the depolarizing print that plant structures left on input polarized beams, the potential of polarimetric methods has not been properly exploited. In fact, among the few works dealing with polarization and plants, most of them study light scattered by plants using the Degree of Polarization (DoP) indicator. Other more powerful depolarization metrics are nowadays neglected. In this context, we highlight the potential of different depolarization metrics obtained using the Mueller matrix (MM) measurement: the Depolarization Index and the Indices of Polarimetric Purity. We perform a qualitative and quantitative comparison between DoP- and MM-based images by studying a particular plant, the Hedera maroccana. We show how Mueller-based metrics are generally more suitable in terms of contrast than DoP-based measurements. The potential of polarimetric measurements in the study of plants is highlighted in this work, suggesting they can be applied to the characterization of plants, plant taxonomy, water stress in plants, and other botanical studies.

Influence of temporal averaging in the performance of a rotating retarder imaging Stokes polarimeter

“…Dark intensity noise, as shown in Eq. (13), depends on the integration time ∆t: u dark = I dark ∆t. We are interested in relating it with the integration angle interval, which is the magnitude analyzed in the figures of the paper.…”

“…There are applications, such as in tissue structural analysis [3,[13][14][15][16], where various illumination wavelengths are used. If a conventional non-achromatic retarder is applied, the effective retarder retardance changes with the applied wavelength.…”

Accurate polarization preparation and measurement using twisted nematic liquid crystals

“…Light reflection and scattering is fundamanetally affected by incident polarization [1]. Manipulating the state of polarization can significantly improve optical resolution [2] and visualization of anisotropic structures in biomedical imaging [3,4]. Polarization modulation enhances information capacity in optical communication [5] and represents a building block of quantum communication and quantum information processing [6,7].…”

Training in polarization through a virtual learning environment

“…For this reason, polarimetry, being the measurement and interpretation of the polarization of transverse waves or of the polarimetric transfer function of materials, is widely used in a large number of applications, as for instance, for the characterization of the optical parameters (index of refraction, thickness, absorption coefficient, roughness, etc.) of materials structured in thin films [2][3][4][5] , in remote sensing 6 , applications in astronomy 7,8 , for medical applications 9,10 , in biophotonics [11][12][13][14][15][16] , among many others.…”