Noise creates polarization artefacts

Temple

How

et al. 2018

Sci Nat

In recent years, the study of polarisation vision in animals has seen numerous breakthroughs, not just in terms of what is known about the function of this sensory ability, but also in the experimental methods by which polarisation can be controlled, presented and measured. Once thought to be limited to only a few animal species, polarisation sensitivity is now known to be widespread across many taxonomic groups, and advances in experimental techniques are, in part, responsible for these discoveries. Nevertheless, its study remains challenging, perhaps because of our own poor sensitivity to the polarisation of light, but equally as a result of the slow spread of new practices and methodological innovations within the field. In this review, we introduce the most important steps in designing and calibrating polarised stimuli, within the broader context of areas of current research and the applications of new techniques to key questions. Our aim is to provide a constructive guide to help researchers, particularly those with no background in the physics of polarisation, to design robust experiments that are free from confounding factors.

Section: How Polarised Light Is Measuredmentioning

confidence: 99%

Polarisation vision: overcoming challenges of working with a property of light we barely see

Temple

How

et al. 2018

Sci Nat

“…Polarization was measured at the same position using a UV-transmissive calcite linear polarizer (Glan-Thompson; GTH5M-A: Thorlabs GmbH, Germany) coupled to a spectrometer (FLAME-S-UV-VIS) via a light guide (P1000-2-UV-VIS; Ocean Optics). Spectra were recorded for four polarizer orientations in order to estimate Stokes parameters S 1 and S 2 (Foster et al ., 2018) and each measurement repeated ten times and averaged (Supplement S1.2) to minimise the effects of sensor noise (Tibbs et al ., 2018). Prior to Stokes parameter estimation, median spectrometer response for each polarizer orientation was weighted by the absorption spectrum of an insect photopigment with a maximum absorbance at 365 nm, calculated using the Stavenga template (Stavenga, 2010), and integrated across the region of the spectrum from 380–450 nm.…”

Section: Methodsmentioning

confidence: 99%

Orienting to Polarized Light at Night—Matching Lunar Skylight to Performance in a Nocturnal Beetle

Kirwan

Jundi

et al. 2018

Preprint

A degree-of-polarization threshold for orientation behaviour is 15 reported for nocturnal dung beetle Escarabaeus satyrus in the context 16 of measurements showing changes in the degree of polarization of 17 skylight with lunar phase. 18 Abstract 19For polarized light to inform behaviour, the typical range of degrees of 20 polarization observable in the animal's natural environment must be 21 above the threshold for detection and interpretation. Here we present 22 the first investigation of the degree of linear polarization threshold for 23 orientation behaviour in a nocturnal species, with specific reference to 24 the range of degrees of polarization measured in the night sky. An 25 effect of lunar phase on the degree of polarization of skylight was 26 found, with smaller illuminated fractions of the moon's surface 27 corresponding to lower degrees of polarization in the night sky. We 28 found that South African dung beetle Escarabaeus satyrus 29 (Boheman, 1860) can orient to polarized light for a range of 30 degrees of polarization similar to that observed in diurnal insects, 31 reaching a lower threshold between 0.04 and 0.32, possibly as low as 32 2 0.11. For degrees of polarization lower than 0.23, as measured on a 33 crescent moon night, orientation performance was considerably 34 weaker than that observed for completely linearly-polarized stimuli, 35 but was nonetheless stronger than in the absence of polarized light. 36

“…Spectra were recorded for four polarizer orientations in order to estimate Stokes parameters S 1 and S 2 (Foster et al, 2018) and each measurement was repeated 10 times and averaged ( Fig. S2) to minimize the effects of sensor noise (Tibbs et al, 2018). Prior to Stokes parameter estimation, median spectrometer response for each polarizer orientation was weighted by the absorption spectrum of an insect photopigment with maximum absorbance at 365 nm, calculated using the Stavenga template (Stavenga, 2010), and integrated across the region of the spectrum from 380 to 450 nm.…”

Section: Polarized Light Stimulusmentioning

confidence: 99%

Orienting to polarized light at night—matching lunar skylight to performance in a nocturnal beetle

Journal of Experimental Biology

Kirwan

Jundi

et al. 2018

For polarized light to inform behaviour, the typical range of degrees of polarization observable in the animal's natural environment must be above the threshold for detection and interpretation. Here, we present the first investigation of the degree of linear polarization threshold for orientation behaviour in a nocturnal species, with specific reference to the range of degrees of polarization measured in the night sky. An effect of lunar phase on the degree of polarization of skylight was found, with smaller illuminated fractions of the moon's surface corresponding to lower degrees of polarization in the night sky. We found that the South African dung beetle Escarabaeus satyrus can orient to polarized light for a range of degrees of polarization similar to that observed in diurnal insects, reaching a lower threshold between 0.04 and 0.32, possibly as low as 0.11. For degrees of polarization lower than 0.23, as measured on a crescent moon night, orientation performance was considerably weaker than that observed for completely linearly polarized stimuli, but was nonetheless stronger than in the absence of polarized light.