Extracting Infrared Absolute Reflectance from Relative Reflectance Measurements

2012 ◽  
Vol 66 (6) ◽  
pp. 680-684
Author(s):  
Susan L. Berets ◽  
Milan Milosevic
Keyword(s):  
Absolute Reflectance ◽  
Reflectance Measurements

Absolute reflectance measurements by a modified cavity phase-shift method

2002 ◽  
Vol 73 (4) ◽  
pp. 1697-1701
Author(s):  
S. Mogg ◽  
N. Chitica ◽  
G. Plaine ◽  
M. Hammar
Keyword(s):  
Phase Shift ◽  
Shift Method ◽  
Phase Shift Method ◽  
Absolute Reflectance ◽  
Reflectance Measurements

scholarly journals Reflectometers for Absolute and Relative Reflectance Measurements in the Mid-IR Region at Vacuum

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1169
Author(s):  
Jinhwa Gene ◽  
Min Yong Jeon ◽  
Sun Do Lim
Keyword(s):  
Fourier Transform ◽  
Diffuse Reflectance ◽  
Standard Uncertainty ◽  
Integrating Sphere ◽  
The Third ◽  
Systematic Uncertainties ◽  
Infrared Spectrometer ◽  
Reflecting Surfaces ◽  
Absolute Reflectance ◽  
Reflectance Measurements

We demonstrated spectral reflectometers for two types of reflectances, absolute and relative, of diffusely reflecting surfaces in directional-hemispherical geometry. Both are built based on the integrating sphere method with a Fourier-transform infrared spectrometer operating in a vacuum. The third Taylor method is dedicated to the reflectometer for absolute reflectance, by which absolute spectral diffuse reflectance scales of homemade reference plates are realized. With the reflectometer for relative reflectance, we achieved spectral diffuse reflectance scales of various samples including concrete, polystyrene, and salt plates by comparing against the reference standards. We conducted ray-tracing simulations to quantify systematic uncertainties and evaluated the overall standard uncertainty to be 2.18% (k = 1) and 2.99% (k = 1) for the absolute and relative reflectance measurements, respectively.

Optical properties of potassium acid phthalate

1997 ◽  
Vol 12 (5) ◽  
pp. 1262-1267 ◽  
Author(s):  
Davide Comoretto ◽  
Laura Rossi ◽  
Alessandro Borghesi
Keyword(s):  
Optical Properties ◽  
Near Infrared ◽  
Normal Incidence ◽  
Infrared Region ◽  
Visible Range ◽  
Direct Inversion ◽  
Potassium Acid Phthalate ◽  
Absolute Reflectance ◽  
Reflectance Measurements ◽  
Acid Phthalate

Potassium acid phthalate (KAP) crystals are promising as substrates for the growth of highly oriented films of conjugated polymers with exceedingly high and fast nonlinear optical response. We report the KAP optical properties (real and imaginary parts of the refractive index ñ = n + ik) in the near infrared and visible range deduced by ellipsometric measurements and direct inversion of transmittance and near-normal incidence absolute reflectance measurements. In the infrared region n was also deduced by the interference fringes.

A simplified two layer model for light diffuse reflectance in thin skin fruits

2010 ◽  
Vol 6 (1) ◽  
pp. 35-72 ◽  
Author(s):  
António Brázio ◽  
Ana Cavaco ◽  
Rui Guerra
Keyword(s):  
Diffuse Reflectance ◽  
Incident Beam ◽  
Layer Model ◽  
Total Reflectance ◽  
Spatially Resolved ◽  
Thin Skin ◽  
Two Layer Model ◽  
Absolute Reflectance ◽  
Reflectance Measurements ◽  
Reflectance Profile

A simple model of light diffuse reflectance in thin skin fruits is presented. The model is based in a semi-infinite two-layer geometry (skin and flesh) and introduces simplifications due to the fact that the first layer is very thin. The flesh is described in terms of the usual reduced scattering and absorption coefficients µs′ and µa but the skin is modeled by simple reflection (R), absorption (A) and transmission (T) coefficients. The problem of diffuse reflectance is thus reduced to the problem of determining the four constants µs′, µa, R and T. It is shown that the problem can be solved by using absolute reflectance and spatially resolved reflectance measurements simultaneously. The coefficients µs′ and µa are determined by the usual fit of the diffuse reflectance profile (photons re-emitted from the flesh far from the incidence point) to the diffusion approximation. The coefficients R and T are determined by a second fit involving the total reflectance profile (photons reemitted both from skin and flesh), the incident beam profile and the diffuse reflectance profile calculated according to the previously determined values of µs′ and µa. The anisotropy of the light re-emitted by the fruit can also be roughly compared with the Lambertian expected behavior. In order to test the model we have followed a population of 22 ‘Rocha’ pears along a period of two weeks. We have then performed the population averages along the time and checked the plausibility of the values obtained for µs′, µa, R and T according to the expected fruit physiological changes along ripening. The results show that all parameters are physically acceptable and evolve in time according to the expected fruit ripening physiology.

scholarly journals The Colors of Mixtures of Dental Opaque Porcelains

1989 ◽  
Vol 68 (9) ◽  
pp. 1319-1322 ◽  
Author(s):  
J.M. White ◽  
W.J. O'Brien
Keyword(s):  
Color Space ◽  
Human Tooth ◽  
Integrating Sphere ◽  
Vertical Movements ◽  
Tooth Color ◽  
B Values ◽  
Color Range ◽  
Standard Observer ◽  
Absolute Reflectance ◽  
Reflectance Measurements

The colors of mixtures of dental opaque porcelains and modifiers were measured with use of the CIE L*a * b* uniform color space. Mixtures of dental porcelains were tested to duplicate the range of human tooth colors. Vertical movements in the yellow and blue directions were obtained. Horizontal movements in the red and green directions were achieved. Reflectance measurements were made with use of a spectrophotometer with an integrating sphere. Spectrophotometer measurements were converted to absolute reflectance and then used to calculate CIE a* b* values for a 2° standard observer and for illuminant C. Movements in the yellow, red, blue, and green directions for adequate simulation of the tooth color range can be demonstrated with use of dental opaque and modifier porcelains.

Forensic applications of IR infrared microscopic internal reflection spectroscopy

1992 ◽  
Vol 50 (2) ◽  
pp. 1528-1529
Author(s):  
Edward G. Bartick ◽  
John A. Reffner
Keyword(s):  
Specular Reflection ◽  
Forensic Analysis ◽  
Attenuated Total Reflection ◽  
Internal Reflection ◽  
Standard Size ◽  
Ir Microscopy ◽  
Ir Analysis ◽  
Plastic Explosives ◽  
Internal Reflection Spectroscopy ◽  
Reflectance Measurements

Since the introduction of commercial Fourier transform infrared (FTIR) microscopic systems in 1983, IR microscopy has developed as an important analytical tool in research, industry and forensic analysis. Because of the frequent encounter of small quantities of physical evidence found at crime scenes, spectroscopic IR microscopes have proven particularly valuable for forensic applications. Transmittance and reflectance measurements have proven very useful. Reflection-absorption, specular reflection, and diffuse reflection have all been applied. However, it has been only very recently that an internal reflection (IRS) objective has been commercially introduced.The IRS method, also known as attenuated total reflection (ATR), has proven very useful for IR analysis of standard size samples. The method has been applied to adhesive tapes, plastic explosives, and general applications in the analysis of opaque materials found as evidence. The small quantities or uncontaminated areas of specimens frequently found requiring forensic analysis will often be directly applicable to microscopic IRS analysis.

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