Diffuse Reflectance and Transmittance

Höpe, Andreas

doi:10.1016/b978-0-12-386022-4.00006-6

Cited by 23 publications

(19 citation statements)

References 38 publications

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“…Larger spheres scatter the light more uniformly than smaller ones . Because of this, the measured total amount of light reflected/transmitted on a sample is better averaged, which is known as better spatial integration of the light emanating from the sample .…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic evaluation of the colour play effect of thermochromic liquid crystal printing inks

Jakovljević

Lozo

Gunde

2016

Coloration Technology

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Colour changes of a thermochromic liquid crystal (TLC) ink printed on a black substrate are clearly observed by the naked eye, and therefore it is reasonable to expect that every approach recommended for colour measurements of samples with solid colour would be appropriate. In addition, the published spectroscopic analyses of TLC inks do not provide any guidance or limitations for the measurement geometry. On the other hand, our study demonstrates that spectroscopic measurements of such samples are not so straightforward. When using the most simple and commonly used measurement equipment with a directional illumination and viewing approach, the temperature‐dependent spectral features resolve in a narrow spectral region that gives only a small part of the colour play effect. Detection of the entire effect requires the use of integrating spheres, which spatially integrate the radiant flux reflected on a sample in any direction; better results are obtained by spheres of larger diameter. The comparision of spectroscopic and colorimetric results obtained when different measurement geometries are applied on the same sample may demonstrate certain properties of the liquid crystal material inside microcapsules and help in understanding some details of the optical properties of the ink layer.

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Section: Resultsmentioning

confidence: 99%

Spectroscopic evaluation of the colour play effect of thermochromic liquid crystal printing inks

Jakovljević

Lozo

Gunde

2016

Coloration Technology

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“…• Irregularities of the sample-surface: bumps, gaps or slants. Remitted intensities change considerably under grazed incidence angles as quantified by Lambert's Cosine law [1,3]. With a severely disturbed matte surface, Lambertian behavior cannot be assumed anymore and diffuse reflectance is affected by geometrical instead of material specific effects.…”

Section: Experimental Difficultiesmentioning

confidence: 99%

“…Diffuse reflectance spectroscopy (DRS) of (nanoscaled) powders is a widely applied, powerful tool in material sciences and industry [1][2][3]. The scattered intensity of an incident light beam is scanned as a function of the wavelength over the sample and the data set is analyzed with respect to its macroscopic optical characteristics, such as the overall reflectivity.…”

Section: Introductionmentioning

confidence: 99%

“…The success in the determination of the absorption features goes along with a thorough knowledge on the relation between the diffusely reflected (remitted) signal intensity and the optical properties of the dielectric materials as well as the powder characteristics including particle size distribution and filling factor. The particular type of light-interaction with powders has been addressed worldwide in a series of theoretical studies over the last decades (cf., e.g., [1][2][3][4][5][6][7][8][9][10][11][12][13][14]). Alike, an innumerable amount of experimental methods and procedures for powder sample preparation have been developed and can be found as an established state-of-the-art tool in nearly any physico-chemical laboratory today.…”

Section: Introductionmentioning

confidence: 99%

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Absorption and Remission Characterization of Pure, Dielectric (Nano-)Powders Using Diffuse Reflectance Spectroscopy: An End-To-End Instruction

et al. 2019

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This paper addresses the challenging task of optical characterization of pure, dielectric (nano-)powders with the aim to provide an end-to-end instruction from appropriate sample preparation up to the determination of material remission and absorption spectra. We succeeded in establishing an innovative preparation procedure to reproducibly obtain powder pellet samples with an ideal Lambertian scattering behavior. As a result, a procedure based on diffuse reflectance spectroscopy was developed that allows for (i) performing reproducible and artifact-free, high-quality measurements as well as (ii) a thorough optical analysis using Monte Carlo and Mie scattering simulations yielding the absorption spectrum in the visible spectral range. The procedure is valid for the particular case of powders that can be compressed into thick, non-translucent pellets and neither requires embedding of the dielectric (nano-)powders within an appropriate host matrix for measurements nor the use of integrating spheres. The reduced spectroscopic procedure minimizes the large number of sources for errors, enables an in-depth understanding of non-avoidable artifacts and is of particular advantage in the field of material sciences, i.e., for getting first insights to the optical features of a newly synthesized, pure dielectric powder, but also as an inline inspection tool for massively parallelised material characterization.

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“…In order to determine the aperture absorption, we measured the reflectance of one of the apertures using a commercial spectrophotometer in an 8°:di-configuration (that is, 8° angle of incidence, hemispherical collection with both specular and diffuse components included. )[17] The results of this reflectance measurement are shown in Fig. 5.…”

Section: Calculating Cavity Absorptance From Dhrmentioning

confidence: 99%

Optical reflectance of pyrheliometer absorption cavities: progress toward SI-traceable measurements of solar irradiance

et al. 2016

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We have accurately determined the absorptance of three pyrheliometer cavities at 532 nm by measuring the residual reflectance using an angle-resolved bidirectional reflectometer. Measurements were performed at normal incidence as a function of viewing angle and position on the cavity cone. By numerically integrating the measured angle resolved scatter (ARS) over both direction and position and accounting for an obstructed view of the cavity, we determined that the effective cavity reflectance was between 8 × 10−4 and 9 × 10−4. Thus, the absorptance of the three cavities ranged from 0.99909 ± 0.00014 to 0.99922 ± 0.00012 (k = 2 combined expanded uncertainties). These measurements, when extended over the spectral range of operation of the pyrheliometer, are required to establish SI traceability for absolute solar irradiance measurements.

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Diffuse Reflectance and Transmittance

Cited by 23 publications

References 38 publications

Spectroscopic evaluation of the colour play effect of thermochromic liquid crystal printing inks

Spectroscopic evaluation of the colour play effect of thermochromic liquid crystal printing inks

Absorption and Remission Characterization of Pure, Dielectric (Nano-)Powders Using Diffuse Reflectance Spectroscopy: An End-To-End Instruction

Optical reflectance of pyrheliometer absorption cavities: progress toward SI-traceable measurements of solar irradiance

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