scholarly journals Laser Imaging Nephelometer for aircraft deployment

2021 ◽  
Author(s):  
Adam T. Ahern ◽  
Frank Erdesz ◽  
Nicholas L. Wagner ◽  
Charles A. Brock ◽  
Ming Lyu ◽  
...  
Keyword(s):  
Polarized Light ◽  
Field Measurements ◽  
High Temporal Resolution ◽  
Light Sources ◽  
Laser Imaging ◽  
Instrument Function ◽  
Scattering Coefficients ◽  
Smoke Plumes ◽  
Linearly Polarized ◽  
Polarization Of Light

Abstract. Validation of remote sensing retrievals of aerosol microphysical and optical properties requires in situ measurements of the same properties. We present here an improved imaging nephelometer for measuring the directionality and polarization of light (i.e. polarimetry) scattered at two wavelengths (405 nm and 660 nm) with high temporal resolution. The instrument was designed for airborne deployment and is capable of ground-based measurements as well. The Laser Imaging Nephelometer (LiNeph) uses two orthogonal detectors with wide-angle lenses and linearly polarized light sources to measure both the phase function, P11(θ), and degree of linear polarization, -P12/P11(θ). In this work, we will describe the instrument function and calibration, as well as data acquisition and reduction. The instrument was first deployed aboard the NASA DC-8 during the 2019 FIREX-AQ campaign. Here, we present field measurements of smoke plumes that show that the LiNeph has sufficient resolution for 0.24 Hz polarimetric measurements at two wavelengths, 405 and 660 nm, at integrated scattering coefficients ranging from 50–80,000 Mm−1.

scholarly journals Patterns and properties of polarized light in air and water

2011 ◽  
Vol 366 (1565) ◽  
pp. 619-626 ◽  
Author(s):  
Thomas W. Cronin ◽  
Justin Marshall
Keyword(s):  
Polarized Light ◽  
Natural Scenes ◽  
Circularly Polarized Light ◽  
Circularly Polarized ◽  
Current State ◽  
Visual Systems ◽  
The Earth ◽  
Predictable Pattern ◽  
Linearly Polarized ◽  
Polarization Of Light

Natural sources of light are at best weakly polarized, but polarization of light is common in natural scenes in the atmosphere, on the surface of the Earth, and underwater. We review the current state of knowledge concerning how polarization and polarization patterns are formed in nature, emphasizing linearly polarized light. Scattering of sunlight or moonlight in the sky often forms a strongly polarized, stable and predictable pattern used by many animals for orientation and navigation throughout the day, at twilight, and on moonlit nights. By contrast, polarization of light in water, while visible in most directions of view, is generally much weaker. In air, the surfaces of natural objects often reflect partially polarized light, but such reflections are rarer underwater, and multiple-path scattering degrades such polarization within metres. Because polarization in both air and water is produced by scattering, visibility through such media can be enhanced using straightforward polarization-based methods of image recovery, and some living visual systems may use similar methods to improve vision in haze or underwater. Although circularly polarized light is rare in nature, it is produced by the surfaces of some animals, where it may be used in specialized systems of communication.

scholarly journals Light Intensity Control Using Polaroids

2022 ◽  
Vol 10 (1) ◽  
pp. 585-589
Author(s):  
Mansi Kadam
Keyword(s):  
Light Intensity ◽  
Light Wave ◽  
Polarized Light ◽  
Light Sources ◽  
Variable Intensity ◽  
Unpolarized Light ◽  
Propagation Of Light ◽  
Intensity Control ◽  
Pass Through ◽  
Polarization Of Light

Abstract: In today’s era of illuminating devices, there are a wide variety of devices available in aesthetics but the none with variable intensity of light. Using the basic principle of polarization of light using a Polaroid filter or polarizer, the designing of a light intensity control was done. The polarizing angle of the filter decides the intensity of the light that would pass through the filters. According to the principle of propagation of light, the electric and magnetic vibrations of a light wave occur perpendicularly to each other. A light wave that is vibrating in more than one plane is known as unpolarized light. The light emitted by the sun, by a lamp or a tube light are all unpolarized light sources. The other kind of wave is a polarized wave. A Plane polarized light vibrates on only one plane. The process of transforming unpolarized light into the polarized light is known as polarization. Using the same principle and with the use of a LDR (light dependent resister) as a sensor to sense the intensity of the surrounding light and then rotate the polaroid filter sheets accordingly using a stepper motor for the required change in intensity. The sensing and sending of feedback and subsequent rotation of the Polaroid filter sheets would be automated by ATMEGA32 microcontroller and L293D. Keywords: Polaroids, LDR, Light Variation, ATMEGA32, L293D

scholarly journals Why do horseflies need polarization vision for host detection? Polarization helps tabanid flies to select sunlit dark host animals from the dark patches of the visual environment

2017 ◽  
Vol 4 (11) ◽  
pp. 170735 ◽  
Author(s):  
Gábor Horváth ◽  
Tamás Szörényi ◽  
Ádám Pereszlényi ◽  
Balázs Gerics ◽  
Ramón Hegedüs ◽  
...  
Keyword(s):  
Polarized Light ◽  
Degree Of Polarization ◽  
Polarization Sensitivity ◽  
Host Animal ◽  
Linearly Polarized ◽  
Imaging Polarimetry ◽  
Host Detection ◽  
Vegetation Region ◽  
Two Parameters ◽  
Polarization Of Light

Horseflies (Tabanidae) are polarotactic, being attracted to linearly polarized light when searching for water or host animals. Although it is well known that horseflies prefer sunlit dark and strongly polarizing hosts, the reason for this preference is unknown. According to our hypothesis, horseflies use their polarization sensitivity to look for targets with higher degrees of polarization in their optical environment, which as a result facilitates detection of sunlit dark host animals. In this work, we tested this hypothesis. Using imaging polarimetry, we measured the reflection–polarization patterns of a dark host model and a living black cow under various illumination conditions and with different vegetation backgrounds. We focused on the intensity and degree of polarization of light originating from dark patches of vegetation and the dark model/cow. We compared the chances of successful host selection based on either intensity or degree of polarization of the target and the combination of these two parameters. We show that the use of polarization information considerably increases the effectiveness of visual detection of dark host animals even in front of sunny–shady–patchy vegetation. Differentiation between a weakly polarizing, shady (dark) vegetation region and a sunlit, highly polarizing dark host animal increases the efficiency of host search by horseflies.

scholarly journals Metasurface of Combined Semicircular Rings with Orthogonal Slit Pairs for Generation of Dual Vector Beams

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1718
Author(s):  
Qian Kong ◽  
Manna Gu ◽  
Xiangyu Zeng ◽  
Rui Sun ◽  
Yuqin Zhang ◽  
...  
Keyword(s):  
Time Domain ◽  
Finite Difference Time Domain ◽  
Polarized Light ◽  
Orientation Angle ◽  
Fdtd Simulation ◽  
Dual Vector ◽  
Vector Beams ◽  
Linearly Polarized ◽  
Potential Applications ◽  
Difference Time

Manipulation of multichannel vector beams (VBs) with metasurfaces is an important topic and holds potential applications in information technology. In this paper, we propose a novel metasurface for the generation of dual VBs, which is composed of orthogonal slit pairs arranged on multiple groups of combined semicircular rings (CSRs). A group of CSRs include a right-shifted set and a left-shifted set of semicircular rings, and each set of semicircular rings has two halves of circles with different radii, sharing the same shifted center. Under the illumination of linearly polarized light, the two shifted sets of semicircular rings generate the two VBs at the shifted center positions on the observation plane. The slit units of each set are designed with independent rotation order and initial orientation angle. By adjusting the linear polarization of illumination, both two VBs with their orders and polarization states are independently controlled simultaneously. The principle and design are demonstrated by the finite-difference time domain (FDTD) simulation. The work is of significance for miniatured devices of VB generators and for related applications.

scholarly journals Formation of half-period surface relief gratings in azobenzene containing polymer films

2020 ◽  
Vol 126 (9) ◽  
Author(s):  
Joachim Jelken ◽  
Carsten Henkel ◽  
Svetlana Santer
Keyword(s):  
Polymer Film ◽  
Polymer Films ◽  
Surface Relief ◽  
Incident Light ◽  
Glassy State ◽  
Polarized Light ◽  
Half Period ◽  
Polarization Distribution ◽  
Linearly Polarized ◽  
Set Up

Abstract We study the peculiar response of photo-sensitive polymer films irradiated with a certain type of interference pattern where one interfering beam is S-polarized, while the second one is P-polarized. The polymer film, although in a glassy state, deforms following the local polarization distribution of the incident light, and a surface relief grating (SRG) appears whose period is half the optical one. All other types of interference patterns result in the matching of both periods. The topographical response is triggered by the alignment of photo-responsive azobenzene containing polymer side chains orthogonal to the local electrical field, resulting in a bulk birefringence grating (BBG). We investigate the process of dual grating formation (SRG and BBG) in a polymer film utilizing a dedicated set-up that combines probe beam diffraction and atomic force microscopy (AFM) measurements, and permits acquiring in situ and in real-time information about changes in local topography and birefringence. We find that the SRG maxima appear at the positions of linearly polarized light (tilted by 45° relative to the grating vector), causing the formation of the half-period topography. This permits to inscribe symmetric and asymmetric topography gratings with sub-wavelength period, while changing only slightly the polarization of one of the interfering beams. We demonstrate an easy generation of sawtooth profiles (blazed gratings) with adjustable shape. With these results, we have taken a significant step in understanding the photo-induced deformation of azo-polymer films.

Study of orientational order of some nematogenic compounds by spectroscopy methods using linearly polarized light

2005 ◽  
Vol 744-747 ◽  
pp. 307-313 ◽  
Author(s):  
D. Bauman ◽  
E. Chrzumnicka ◽  
E. Mykowska ◽  
M. Szybowicz ◽  
N. Grzelczak
Keyword(s):  
Orientational Order ◽  
Polarized Light ◽  
Linearly Polarized

scholarly journals III. On the Plane and Angle of Polarization of Light Reflected at the surface of a Crystal

1844 ◽  
Vol 15 (1) ◽  
pp. 37-65
Author(s):  
P. Kelland
Keyword(s):  
Polarized Light ◽  
The Subject ◽  
Polarization Of Light

The present Memoir is, to a certain extent, a continuation of one which the author presented to the Society in December 1838, and which has since been published in the thirteenth volume of the Transactions. Other motives, however, than the desire of completing the subject, have influenced him in producing the following analysis. A very important point in the hypothetical conditions which Fresnel assumed to hold with respect to polarized light, has, of late, been warmly combated in various quarters. Fresnel supposed that light polarized in a given plane consists of vibrations of such a nature that the motion is perpendicular to that plane. Neumann and other writers contend that the very opposite is the fact. We hope to be able to offer evidence of some little weight in favour of the former view; at the same time we do not pretend to shew the actual impossibility of the truth of the latter.

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