Questions related to Reflectance Spectroscopy
I study on some kind of infrared barrier and I don't know how to calculate normalized reflectance spectra weighted by human body radiation?
For example you can see results of this article but authors did not mention the calculation method:
I have come across a few machine learning algorithms, for prediction of soil chemical properties such as pH, EC, Available nutrients. But, rarely the use of diffuse reflectance spectroscopy assisted by machine learning algorithms. can anyone suggest me some papers regarding the application of different ML techniques in Pre-processing and prediction of pedological properties in hyperspectral imagery.
I am currently designing an optical setup to perform measurements of reflected light (BRDF actually) and I am asking myself if I should consider a "focused on-sample" light beam or a collimated one. What are the influence of collimated and/or focused light on the signal after reflection ?
PS : I am considering diffuse reflection.
Thank you very much
either low or high band gap will give good NLO properties?
I have synthesised boron compounds and I investigated the band gap values using diffuse reflectance spectroscopy further I want to go for SHG NLO application. Thus how to help the band gap values for NLO application.......
Dear more experienced colleagues,
I do external reflection FTIR measurement of waxes on a polyethylene substrate (ski waxes on UHMWPE ski base). I'm wondering why peaks associated with for example C-F stretching peaks in case of fluorinated wax, or Si-O-Si and Si-C peaks in case of silicone-based wax do not have the derivative-like shape (as clearly seen for C-H peaks in the spectra), which is associated with the surface reflection. The shape has rather transmission/absorbtion-like shape, but is pointing up towards higher reflectance and not down, as would be the case if the IR light would be reflected from the PE substrate (which is not expected due to the similar refractive indexes of the waxes and the PE substrate). What is the physical explanation of such behaviour?
Thank you for any help!
Two years ago, during my PhD defense one of the members of the committee asked me what diffuse reflectance is. I said diffuse reflectance is a type of surface reflectance (the other is specular reflectance) whose angle of reflection is independent on the angle of incident radiation. Diffuse reflectance is often observed with radiation incident on a mat or dull surface such as paper, tissues whereas specular reflectance is observed with radiation incident on a polished surface such as a mirror. This is a perfect text book definition
(ref Optical thermal response of laser irradiated tissue, A J Welch or Modern techniques in applied molecular spectroscopy by F. Mirabella)
However, my answer did not sit well with the committee, especially the “surface” part. They argued if diffuse reflectance is a surface reflectance than why diffuse reflectance spectroscopy (DRS) is used to detect tissue abnormality 300-400 micron underneath the surface? They came to agree that diffuse reflectance is “radiation that undergoes scattering and absorption events in tissue and comes back to the surface to be detected by detector”
Just a few days ago, the same question is asked: what is diffuse reflectance? My answer is the same. Once again, there was lots of confusion.
Today, to put my mind to rest I am posting my explanation here. Again, diffuse reflectance is a type of surface reflectance (nobody can change that definition). The name diffuse reflectance spectroscopy (DRS) itself is quite confusing.
DRS collects not only the diffuse reflectance but also the remission. In clinical application of DRS, remission is frankly much more important because it tells us how light propagates within the tissue, and thus help us draw a picture of tissue components (scatterer, absorber). By the textbook, remission is the process in which light is scattered within the tissue, leaving tissue and propagating toward the detector. Therefore, remission is the result of complicated light propagation within the tissue.
This is, partially, why fiber optics DRS with fiber tip in contact with tissue plays an important role. The math is complicated. Principally, contact point of measurement DRS reduces chances to collect surface reflectance and increases chance to collect remission. DRS gave out-standing spectral resolution but not so much spatial information. So, there comes bundle of fibers in an optical probe that likely give enough spatial information to detect tumor margin.
Two tissue samples with different optical properties but same surface structure will have similar diffuse reflectance but different remission. As the results, different DRS signal is collected.
Next topic: Raw fluorescence signal that was not corrected for tissue attenuation is useless.
I need information concerning the penetration and reflection capacity of ultraviolet and infrared radiation wavelengths on different most common materials.
Can somebody recommend a book to learn about? I'm especially interested in spectrogroscopy with a city environment materials and albedo.
USGS provide two kind of major Data sets, which are collection 01- Level 01 and Level-02 data. In Level-02 data All the other visual bands are process to surface reflectance but why panchromatic band isn't process? My question is how to process panchromatic band to surface reflectance? Can you suggest the method for me?
Reflectance can be used for remote-sensing of the presence of algae in water bodies. But is there any advantage in using reflectance over absorbance in the laboratory settings? I am interested in measuring algal pigment composition and content.What additional or superior information can I get from reflectance compared to absorbance?
I measured the transmissivity, absorptivity, and reflectance
parameters of samples using a Jasco V-670 UV-VIS-NIR Spectrophotometer. However, the reflectance values seemed unusual and incorrect.
The reflectance of a crystalline silicon (c-Si) 500 μm thick 2" wafer was measured for the region 0.25 μm to 1.8 μm. However, reflectance was reported as > 100% between 1.2 μm to 1.8 μm and 0.25 μm to 0.36 μm, with the overall mean reflectance for the measured spectra is 127%. See figure attached.
As I understand it, there are a few possibilities for what could be happening here: (a) a poor baseline that contains significant absorbances in the regions in question; (b) emission from the sample; (c) the device itself might need a different accessory to measure specular reflectance; or (d) high levels of specular reflection.
Of the four possibilities, I believe (d) is the most likely. The background reference used will have had very little specular reflection, but as the c-Si sample is a smooth, polished surface it might be quite high. A description of the issues this specular reflectance can cause is described by Blitz . He also discusses the fact that Kubelka-Munk theory ignores specular reflectance completely, which may produce anomalous results.
Has anyone encountered this issue before? And if so, what did you do to solve, mitigate, or overcome the issue? Furthermore, are there perhaps any better alternatives to measure the reflectivity of a smooth, polished sample?
Any help or advice would be appreciated! Thanks in advance.
 J. P. Blitz, “Diffuse Reflectance Spectroscopy,” in Modern Techniques in Applied Molecular Spectroscopy: Techniques in Analytical Chemistry (F. M. Mirabella, ed.), ch. 5, pp. 185–219, New York: John Wiley & Sons, 1998.
HOPG is a good substrate for growth of h-BN. One major application of h-BN is single photon emission which can be used for telecom wavelength. Can anyone give me any insight about the absorption quality(if there is any) of HOPG at 1550 nm.
For polymer film samples, if reflectivity and transmissivity in the mid-infrared region (here, 4 to 16 micrometers) are desired, and using a FTIR & ATR spectrometer (Bomem MB Serie Hartmann & Braun) :
1-Is it possible to use the output spectrum to evaluate the reflectivity and transmissivity?
2-Should not the baseline be corrected by OMNIC Software? Using normalize scale is not allowed?
3-If there are more than 100% reflection in some cases, what corrections should be made? Thanks*
Example: fig 2-f in this article:
I am trying to calculate the optical band gap, valance and conduction band energy levels of my sample. I found that optical band gap can be calculated using kubelka-munk function and diffuse- reflectance spectroscopy. Also, I find that the valane band energy levels can be driven from valance band XPS method, but i was not able to find more details. So, this is my question:
for calculation of valance band energy using XPS analysis, i need to conduct specific kind of XPS analysis? how i can apply XPS plot to use valance band energy?
When imaging protein solutions (1ug/ml,10ug/ml,100ug/ml,1000ug/ml ; diluted with PBS buffer 7.4) on a gold surface, what is the optimal pretreatment(s) to separate out the effect of the buffer (in my case PBS) which interferes with bands of interest for proteins?
10ul of each concentration was dropped on a clean gold slide and allowed to dry for 24hr under Nitrogen purge, followed by FTIR-reflectance imaging.
Since samples with 1000ug/ml are highly concentrated, their signal appears very clear (Amide I, Amide II, Amide III, Amide A, Amide B), however at concentrations below and = 100ug/ml, protein signature is dominated by PBS buffer bands.
What kind of univariate or multivariate methods would you apply to
(a) identify protein pixels (remove interference of buffer, slide background if any)
(b) quantify protein pixels (eg. make PLSR model on 0ug,1ug,10ug,100ug,1000ug) and predict concentration level of an unknown dried protein sample?
Dear experienced researcher,
I will briefly explain my experiment and then ask two questions I have.
The solution of particular interest is transition metal oxides (TMOs), especially Molybdenum Oxide MoO3. The way I prepare it by using solution synthesis method and thus the actual composition of molybdenum oxide is of the form HyMoOx. Theoretically speaking, the absorption of the HyMoOx should be varying with the change in the oxidation state of Mo, where MoO3 has lowest absorption while HyMoO2 will have more absorption due to reduced bandgap.
What I want to do is to use UV-VIS spectroscopy to characterize the form of the solution. Since, I have no experience in it, I want to go through some literature that uses the same technique to do this or something similar? I failed to find any useful papers about it, if there are, please share them to me?
Second, to characterize the absorption of the solution, a high transparent container should be used. Can any one share with me the high transparent glass container or other container are suitable for this experiment setup?
I have reflectance spectra of a sample. R(w) (reflectance in wavelength 400-1000nm).
in keramers kroning analysis of the reflectance spectra, there is a shift phase integral:
w/pi(Int(ln(R(w))-ln(R(w')) / w^2-w'^2))dw)
I have R(w) but dont know what R(w') is.
Would you please somebody guide me, I interuppted in this part for MATLAB code write.
I cannot understand the difference between radiance and reflectance when measuring vegetation indices like NDVI.
I checked the definitions of Radiance and Reflectance - radiance is the radiation reaching the sensor and reflected by the surface whereas reflectance is the ratio of radiation striking the surface to the radiation reflected by the surface.
As far as I read, its better to calculate indices using surface reflectance values. Radiances are not suitable because they can be inaccurate due to atmospheric effects until the radiation reaches the sensor.
My question is, even if there were no atmospheric effects, how can vegetation index values calculated from radiance be similar to values calculated from reflectance? The two seem to be different things from their definitions. I would assume we would get highly varying vegetation index values.
So how is it still acceptable that people dont bother to convert radiances to reflectances before calculating vegetation indices?
The Labsphere's Spectralon is widely used as a reference when doing spectral measurements. It is close to Lambertian surface but not ideal Lambertian surface, so when doing photometric measurements, the reflectance dependency on emission angles should be corrected.
When the absorbance spectrum is recorded, it is found to be the same as that obtained from diffuse reflectance spectra after performing Kubelka Munk transformation. So, what is the advantage of kubelka munk over absorbance?
The synthesized materials are powders and thus diffuse reflectance was run rather than absorbance. I need to draw up Tauc plots to obtain the band gap. However, I have been struggling with the conversion of my data to the Kubelka-Munk graphs.
I have also tried to download UVProbe software but was unsuccessful.
I want to calculate the percentage content of water/ moisture present in human hair through Near Infrared Spectroscopy. any addition method has to be applied after spectra determinations to calculate exact / approximate water content ?
now i am doing my project based on the abortion of materiel (that material like sand witch modal that means three materials in three layers, i want individual absorption of materials), how to calculate scattering of light, problem is i am doing nano meter range, i want accurate absorption of light in material,excluding scattering losses
I am trying to characterize the surface reflectance of a thick semiconductor (i.e. transmission experiments are not applicable). As the sample is mounted in a cryostat I have no direct access and an integrating sphere cannot be used. Under these circumstances, what is a good way of measuring the surface reflection for extraction of the band-gap of the material (visible region)?
Thank you all in advance for your time and assistance!
Can I use MODIS corrected reflectance (true color) obtained from Worldview to track turbidity front? I do not want to know the concentration, only the position and area. Instead this, do I have to process the image from ocean color page?
Thank you in advance.
Recently,I am studying on the influences about IR light to human beings. Except the absorption curve about human body to IR light,any related information is well and needed.
I fabricate a silicon nanocone array and I want to measure reflectance spectrum but I don’t know exactly what to do. In order to measure the reflectance spectrum, the reference spectrum must be measured. To do this, I can use two kind of standard mirrors, Al mirror (specular) and PTFE mirror (diffuse). But I do not know what standard mirror I have to use for reference spectrum measurement. For this measurement, I use Reflection probe and 10X objective (dimension of nanostructure is 200µm). Could you please guide me how I can measure reflectance spectrum in the reflection geometry from my nanostructures?
I calculate the Reflection spectrum using equation which is attached.
Is it right?
I have done a number of reflectance spectroscopy studies using both a PIMA and more recently the Terraspec to study alteration minerals for epithermal deposits and geothermal systems. Both have smectite, illite-smectite, illite with variable chlorite, calcite and kaolinite. In these studies I have calculated various spectral parameters derived from both reflectance and hull quotient corrected / continuum removed spectra. Curiously, the calculated H2O/Al-OH depth ratio for the epithermal hosted in andesite for reflectance spectra show a better match with XRD results then the hull. However the opposite seems to be the case for the mostly rhyolite hosted geothermals. The shape of the hull differs between the two and it appears that for andesite there is typically a downward slope between 1900 and 2200 nm, whereas for the geothermal this interval is fairly flat / though the overall profile from 1200 to 2500nm is often convex. What is the cause of the continuum shape?
I should add, that the andesites are typically intensely altered and thus pale cream, white to pale - medium green / depending on chlorite content. Altered rhyolite from the geothermal shows the same range of colours.
I am using cary 100 UV-VIS diffuse reflectance spectroscopy with 70mm integrating sphere.when I place the standard in the sample port and measure the reflectance the value I am getting is around 40%.
I am working on rare earth metal perovskite photocatalysts. I want to calculate their band gap using the data from their reflectance spectrum.
I'm just wondering whether there should be a difference in spectra of the same sample taken with the same equipment but in different modes of light transmission say one in reflectance and the other in transmittance but with the same light source! I will appreciate any little explanation in addition to answering this question. Thank you in advance.
I am able to convert wavelength(nm) values to photon energy(eV) but I could not find out how to draw Tauc Plot from these values (i.e., reflectance and photon energy)
measured reflectance peak amplitude decreased, with compared to modeled spectra?
I am confused about how to accurately find out the band gap of a semiconductor using diffuse reflectance curve. I have plotted the data but am bit doubtful about the tangent to be drawn. I am uploading curve and have followed two methods to find band gap using tangent. Please confirm the correct method.
Is the method in image B correct or in B ? If not then how do I proceed.
Landsat products from TM or ETM+ i have been using for LULC change detection . but now a new surface reflectance product is available . Can any body suggest is best use ..???
I am carrying out a lab experiment to see the effect of dry and wet soil on Emitted Radiance. The results are anticipated to help develop an understanding of how soil moisture influences Geothermal anomaly detection in remotely sensed data. To determine the amount of moisture in a soil sample, standard gravimetric method will be followed and the ratio of water content to dry soil will be recorded in %. For the associated Spectral measurements a Fourier Transform Infrared (FT-IR) Spectrometer ( 2.5 to 16 µm ) will be used to retrieve the directional-hemispherical reflectance values and subsequently converted into emissivity using Kirchoff's law. Using emissivity and temperature the Emitted Radiance can be calculated for each soil type in dry and wet states using Planck's black body equation. Emissivity measurements are crucial for accurate land surface temperature estimation.
However, setting-up the experiment requires some careful considerations. For example, it is challenging to keep soil sample homogeneously wet at least as long as the measurements are taken before the top part of the soil dries up. One of the suggestions is to take the spectral and soil moisture measurements quickly to have a good estimation of the soil moisture at the top layer. Since the TIR measurements are restricted only to the top few micrometers/sub millimeters of the soil surface or otherwise known as the skin level, it is essential that the soil moisture measurements correspond to the TIR measurements.
Are there any alternative ways to do the same experiment? What other challenges can be expected?
The wavelengths are 400 to 1000 nm.
I would like to know not the particle's absolute absorbance value just how they relate to each other; which of these particles reflect the most light.
is it correct assumption that the bigger the area of the spectrum is the more löight is being reflexted
I have to set up a phantom study as well as an in vivo study for measuring light reflectance spectra of human tissue using diffuse reflectance spectroscopy technique.
I have to choose up to 4 wavelengths but not sure what wavelengths do I need to perform my experiments.
Need to be mentioned that data obtained from experiments will be used for validating numerical a light propagation numerical model (Monte Carlo).
As my second question, what difference does it make using a LED as a light source instead of laser?
Thank you very much.
Could anyone help with the instrument using for reflectance measurement?
Our Lab has JASCO V-670 instrument and ISV-723 60mm integrating sphere.
But no one knows how to use those things..
And I want take reflectance spectrum using this instrument.
Please help me ;)
I am trying to do a UV-Vis diffuse reflectance measurement using a Perkin Elmer Lambda 750 instrument. Do you have experience with the instrument set up, where and how to put the sample in the holders, what should be used for back ground correction.
I try but could not contact Perkin Elmer for a training.
I attached a photo of the sample compartment for your reference. Please advise!
I have successfully synthesized my nanocomposites with different concentrations. For optical properties i have done Diffuse Reflectance Spectroscopy(UV-Visible). I observe reduction in the Reflectance as well as the band gap of the material as I increase the concentration of second material. So tell me the possible reasons why the band gap and reflectance changed?
Actually I've got the DRS (diffuse reflectance Spectroscopy) results of my samples i.e. WO3 Nanoparticles, and I've applied Kubelka Munk function to get the band gap of my results but its much more than it is reported, the reported results of the band gap of WO3 is from 2.4 eV to 3 eV (max), so I want to know is kubelka-munk function the reliable method to find the band gap of materials?
I have synthesis WO3 nanoparticles. I have characterize my material via DRS for optical properties but it has two peaks. What is the first peak is showing? I have attached a picture also. There are many formulas which can be used to analyze DRS, i.e. KMF, bulk munk and etc. Which one is the best? What kind of properties other than optical properties can be explained using DRS? Kindly attach Pdf files of DRS analysis of WO3 nanoparticles if someone have it.
I'm using RapidEye data to calculate vegetation indices from a cropped area. I'm interested in using this index which has an equation as fellows:
( Red / Near Infrared ) / ( r680 / r800 )
It is clear that red and Near infrared as bands 3 and 5, respectively for RapidEye. But it is not clear what does r680 / r800 mean? I appreciate your assistance.
I have images from a Specim SWIR terrestrial hyperspectral camera, and I have converted them to radiance. I also have FODIS data, which can be used to convert to reflectance, I'm just not quite sure how to do this.
image: n lines, 291 samples, 256 bands.
FODIS data: n lines, 1 sample, 256 bands.
Any suggestions would be greatly appreciated.
Does COMSOL have the same capabilities as the monte carlo method in modeling light-tissue interactions in terms of calculating and obtaining light distribution over the surface as well as inside the tissue in 3D?
We use a Xenon lamp, a monochromator, an integrating sphere and a photodiode to measure the total reflectivity of thin films (metallic, or organo-metallic nanocomposites thin films). I'm looking for a procedure (geometry configuration, reference measurements, data analyzis) to do a reliable measure.
My question is about how to convert the data to percentage or to value that has defined dimension. Also it is nice to be clear if those data could be compared to those from in-situ measurements. Up to now I could not find reference for usage of this product.
I'm using uv-vis reflectance to investigate multilayer structure. The UV-vis light is normal inciedent. The reflectance v.s. wavelength data was than obtain and exhibited a curve with many oscillations. How to analysis/fit the curve to obtain the structural inforamtion, include layer thickness, wavelength dependent refractive index, or maybe layer roughness?
When I calculate the optical gap of my thin films deposited on Corning glass via transmittance UV-Vis-NIR measurements , I find a different value than that I calculated via reflectance UV-Vis-NIR measurement.
I wonder what in the structure or the surface of the film has to be taken in consideration to make Reflectance measurements ????
We have recorded a Diffuse Transmission Reflectance spectrum by keeping the test sample in the entrance of the integrated sphere in %R mode and later converted it in K-M. What is the actual good practice?
Fe(II) complex shows Spin State Cross Over (SSCO)phenomenon. Will it give reflectance spectrum corresponding only to its high spin state or only to its low spin state or simultaneously to both the states at SSCO temperature? Give argument/s.
Hi, I am a beginner in BRDF/Albedo research. And I need to draw a two dimensional plot revealing the relationship between "Bi-directional reflectance" and "view zenith/azimuth angle", just like a plot in the attached picture. Would anyone please tell me how to draw it, with a little bit of detail? Thank you so much!
I have recorded FTIR spectra for my biological sample.
I would like to convert the spectra to reflectance mode .
Is there any conversion formula ?
How much more reliable is the comparison of transmission data and reflectance data for a thin film of polymer coated on ITO/glass and Platinum respectively?
I have data for reflectance vs wavelength by uv vis nir. I want to calculate R∞ for our sample and after that I want to calculate K-M (Kubelka-Munk) function (f(R∞)).
We have reflectance data of multilayer oxide films in which metal film is sandwiched. We want to extract refractive index values of the oxide layers. Is this possible?
The UniSpec-SC is usually used in plant leaf measurements but if it is able to measure Total Reflectance it is possible to use it in any surface, or is it calibrated exclusively to plants? If so, could I adapt it somehow to measurements of animal skin?