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There are many fields where light field can be utilized. For example it is utilized in microscopy [1] and for vision based robot control [2]. Which additional applications do you know?
Thank you in advance!
[1] Li, H., Guo, C. and Jia, S., "High-resolution light-field microscopy," Frontiers in Optics, FW6D. 3 (2017).
[2] Tsai, D., Dansereau, D. G., Peynot, T. and Corke, P. , "Image-Based Visual Servoing With Light Field Cameras," IEEE Robotics and Automation Letters 2(2), 912-919 (2017).
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Hi Vladimir Farber, I think one of the fields of Light Field Images missing to be mentioned is the "Quality Assessment of Light Field Images" when they are propagating through a communication channel. For your kind reference, one of the published papers in this field is :
"Exploiting saliency in quality assessment for light field images."
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Dear professors and colleagues,
I am going to to study effect of the two photons absorption in Safranin O. Safranin O is organic material, so I think that the power needed to activate this effect doesn't need to be too high. However, the two photons absorption is a third-order nonlinear optical effect, so it is usually implemented with high-power pulsed lasers. I cannot afford to buy high-power pulsed lasers. So, can I stimulate effect of two photons absorption in safranin O by continuous wave laser (808 nm or 1064 nm)? And how much is the required power of laser? I hope the colleagues who have experience in this experiment share me useful information.
I look forward to hearing from you. Thanks in advance.
Yours sincerely.
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Dear Nguyen, I beg You pardon, please read with attention my above given advice.. or at least tell us for what task You are going to apply TPA excitation then it would be possible to figure out correctly what laser beam intensity W/mm2 You was needed...
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Dear Colleagues,
I am investigating methods to determine the photodynamic activity of photosensitizers for photodynamic therapy. One of the methods being used is absorption spectrometry. A work concludes that significant absorption of light was shown to be prerequisite but not sufficient for high photodynamic activity. My point of view is: When a photosensitizer absorbs more radiation at a certain wavelength, it will produce more Ros (Reactive oxygen species), i.e the absorption maximum will correspond to the wavelength active photodynamic effect best. However, this point of view contradicts the viewpoint in above work. I look forward colleagues to explain this question.
Thanks in advance.
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Nguyen, It seems reasonable that the greater the absorption efficiency the greater the release of ROS. This applies to both exogenous photosensitizers and endogenous porphyrins. We are preparing a paper describing the absorption spectra of intact, live planktonic pathogens, both bacteria and fungi, collected with diffuse reflection spectroscopy. (Please see our papers: "The Black Bug Myth" and "Selective Photoantisepsis" posted on RG). I propose that these absorption spectra, if obtained in vivo, will mirror the action spectrum (clinical efficacy VS WL) of the clinical application.
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I have three collimated optical beams with 1cm separation between the adjacent one. I want to shift one of the three beam laterally so that it goes closer towards or farther away from the adjacent beam by micrometer accuracy.
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Dear Sreeprasad
If you are not worried about relative phases and can tolerate a number of very weak secondary beams, perhaps the simplest way is to insert a tilted parallel glass plate into the beam you want to translate. The translation of the main transmitted beam will be Theta*T*(n-1)/n, where n is the refractive index of the glass plate, T is its thickness and Theta is the tilt of the plate's normal relative to the beam propagation direction (in radians). A 1 mm thick glass slide at 5 degrees will result in a shift on order of 50 microns. The main drawback from this method is that more than one beam is transmitted due to the multiple reflections at the glass surface, however the main transmitted beam will be several hundred times more intense than the strongest secondary beam.
Good luck
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I am trying to analyse some OCT pullbacks using Osirix, having never used the software before. My aim is to measure CSA at various points of the pullback, and also to semi-quantitatively analyse the plaque characteristics. Any advice will be very hepful
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I think OCT image in the cardiovascular field has been defined by DICOM format.
You should modify open-source version of OsiriX in order to read the format.
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I was wondering how to find non fluorescent plastic coverslips for optical in vivo imaging. We now use glass coverslips 3mm in diameter, 0,15mm thick, but want to find a plastic substitute. According to this paper http://www.ncbi.nlm.nih.gov/pubmed/16286964, PDMS seems to be good. But I cannot find any commercial supplier of coverslips made of this material. Could anyone be so kind to provide some advice?
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This is a very old thread; in the past, I used to purchase plastic sheets of all kind of types from McMaster, the ones that come with a protective film, and test them myself. 100 micron thickness (4 mil) is a very common size for plastics. I remember finding that acetyllellulose used for dialysis had the least amount of fluorescence. I think scientific companies markup their plastic coverglasses by orders of mag, and it's better to just get a roll of plastic and cut it yourself.
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What additional information does the phase measurement in a frequency-domain imaging technique provide compared with the continuous wave technique that measures only the amplitude of the diffuse light?
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A phase shift of a frequency modulated light source is almost equivalent to a change in mean flight time of the photons and hence provides information about the mean free path length of the photons through the tissue. This information is distinct to that provided by a change in amplitude, which is the only variable measured in continuous wave (CW), and helps in distinguishing the degree to which attenuation is a result of either scattering or absorption events. In certain cases, such as diffuse optical tomography, it is possible to separate scattering and absorption using CW measurements by solving a regularised inverse problem, however frequency domain measurements will typically improve this separation by reducing the non-uniqueness.
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Dear colleagues,
The Z-scan technique is proposed by Sheik-Bahae et al [1]. Theoretically, when there is no nonlinear absorption, the Z-scan curve must be symmetric around the origin of the Z-axis. However, in practice, the Z-scan curve usually has a large asymmetry. I know the reason for this phenomenon for thermal-optic nonlinear mechanisms. For the electronic nonlinear mechanism, what are the reasons for this asymmetric phenomenon? (Except for experimental error).
Thank you and hoping for your insightful response.
[1] Sheik-Bahae, Mansoor, et al. "Sensitive measurement of optical nonlinearities using a single beam." IEEE journal of quantum electronics 26.4 (1990): 760-769.
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When the nonlinear response is dominated by the Kerr effect (nonlinear refractive index change) the asymmetry is easy to understand in the limit of thin media. Essentially the Kerr effect induces a "nonlinear lens" in the material which changes the subsequent propagation of the beam. The example you show in your question would correspond to the case of a negative Kerr effect (n2<0). When the sample is placed before the focal plane of the physical lens, the combined effect of the lens originally used to focus the beam and the negative focal length "lens" induced in the sample is to translate the beam's focal plane further along the z-axis. Thus by the time the beam reaches the aperture it has not diverged as much and the transmission through the aperture is higher. Conversely when the sample is placed behind the focal plane of the physical lens, the induced negative lens leads to an increased divergence and consequently a lower transmission at the aperture. It is not just the phase shift, but difference in curvature of the wavefronts on either side of the focus that gives rise tot he assymmetry. You can find a more detailed explanation in the book "Fundamentals of Nonlinear Optics" by Powers and Haus, chapter 8.
Basically the optics is roughly the same as in the thermal lens case. The main difference is that for an electronic nonlinearity in the absence of absorption, the induced lens is an "instantaneous" response to the transverse profile of the incident beam, whereas in the thermal case it is the radial variation of the adsorbed energy convoluted with thermal diffusion that produced the effective lens induced by the incident beam. Of course the detailed shape of the Z-scan curve will be different, due to the difference in the transverse variation of the induced refractive index change in the two cases. In the "instantaneous" electronic case, this variation will follow the radial variation of the incident beam, in the thermal case the balance between the power deposited by the incident beam and diffusion of the heat within the sample will determine the spatial profile of the induced refractive index change.
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I am wondering what is the impact of the presence of edema and/or necrosis on optical coefficients (absorption, scattering, anisotropy coefficients) in a biological tissue?
I cannot find any papers on this subject...
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That is interesting, indeed. Have you tried measuring the absorption coefficient? As far as I know, brain haemodynamics changes have a stronger influence on absorption than on scattering (although that may not be your research field).
Just in case you wish further reading, in this handbook you can find information about brain tumor scattering properties (starting from page 2-41), and other optical parameters, too:
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Distance between object and sensor is 2mm.
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Hey Kamrul, 
I would agree with Indrasen's assessment. I would also suggest to think in terms of spatial frequncies. If your detector is placed in the optical far-field, you will directly measure the Fourier transform. The numercial aperture of your detector will then limit the spatial frequency extent of your Fourier transform, i.e. your detector acts as a low pass filter. If you are measuring with a lensless setup in the optical near-field, you can just as much think in terms of the spatial frequency spectrum by using the angular spectrum formalism (ASPW); the ASPW will lead to the same reasoning as Indrasan's argument above. 
However, in most lensless microscopes you will have to do some sort of phase retrieval that allows you to refocus the wave field into the specimen plane. The ability to successfully do phase retrieval typically depends on some sort of data redundancy (as in ptychography) or a priori knowledge (as in single shot coherent diffraction imaging or holography [where the reference wave is assumed to be known]). Departure from idealized assumptions (a priori knowledge), mathematical models, systematic experimental errors and noise will lead to a decrease in resolution. For this reason, the so called Fourier ring correlation (FRC*) is used in electron microscopy and x-ray ptychography to assess the reproducibilty of computationally retrieved spatial frequency spectra. Let's say you you are computationally reconstructing a microscopic sample with two different randomized initial guesses (assuming some sort of iterative reconstruction algorithm). Then the two different initial guesses will yield two slightly different reconstructions. From my experience in this field, typically the low frequencies are well reconstructed, the high frequencies are less reproducible. But only reproducible spatial frequencies are resolved spatial frequencies. Therefore I would recommend using the FRC for resolution estimation.
Finally, it is always worth taking a resolution test target (such as spokes targets). While those are typically binary test objects  and biological specimen are harder to reconstruct, they give you at least an idea of what the resolution of your microscopes is. 
Having said that, take also a look at this ** reference. Be also aware to always distinguish between half pitch and full pitch resolution (***). Simply stated, if you are able to resolve a harmonic grating (sinusoid), then due to the Shannon-Nyquist sampling criterion it takes two samples per spatial period to digitally represent this signal. Then the half period is the half pitch, the full period is the full pitch. 
Best wishes,
Lars
* Van Heel, M., & Schatz, M. (2005). Fourier shell correlation threshold criteria. Journal of structural biology, 151(3), 250-262.
** Horstmeyer, R., Heintzmann, R., Popescu, G., Waller, L., & Yang, C. (2016). Standardizing the resolution claims for coherent microscopy. Nature Photonics, 10(2), 68.
*** Zheng, G., Horstmeyer, R., & Yang, C. (2015). Corrigendum: Wide-field, high-resolution Fourier ptychographic microscopy. Nature Photonics, 9(9), 621.
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Dear community,
I do not have access in the ICRU report 46 and I am not able to retrieve complete information regarding the tissue composition of prostate, urethra and rectum for a Monte Carlo simulation of brachytherapy that I want to do. Is there any knowledge regarding the composing elements, their ratios and the density of each of these three structures? Any bibliographic reference is also well appreciated.
Thank you in advance,
Konstantinos. 
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I would like to measure optical coefficients (anisotropy, absorption and scattering) of a phantom developed in my lab. However, we just own a 3-port integrating sphere (it does not have a port in front of the entry port of the sphere). So, how can I measure the diffuse reflectance without placing a sample in the exit port (because I do not have an exit port directly in front of the entry port)? Thank you in advance.
Clément.
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Shigeo, thank you again for your answer.
When I mentioned “without sample”, I meant “with the quartz cuvette placed in the optical bench but empty, without the intralipid liquid inside”. Thus, I hoped to avoid specular reflection noise due to interfaces air/quartz/sample/quartz...
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I'd like to hear from anybody who used/developed laser scalpels: general descriptions, types of surgeries, clinicians feedback, references.
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Coagulation and ablation of biological soft tissue by quantum cascade laser with peak wavelength of 5.7 μm.
Molecules such as water, proteins and lipids that are contained in biological tissue absorb mid-infrared (MIR) light, which allows such light to be used in laser surgical treatment. Esters, amides and water exhibit strong absorption bands in the 5–7 μm wavelength range, but at present there are no lasers in clinical use that can emit in this range. Therefore, the present study focused on the quantum cascade laser (QCL), which is a new type of semiconductor laser that can emit at MIR wavelengths and has recently achieved high output power. A high-power QCL with a peak wavelength of 5.7 μm was evaluated for use as a laser scalpel for ablating biological soft tissue. The interaction of the laser beam with chicken breast tissue was compared to a conventional CO2 laser, based on surface and cross-sectional images. The QCL was found to have sufficient power to ablate soft tissue, and its coagulation, carbonization and ablation effects were similar to those for the CO2 laser. The QCL also induced comparable photothermal effects because it acted as a pseudo-continuous wave laser due to its low peak power. A QCL can therefore be used as an effective laser scalpel, and also offers the possibility of less invasive treatment by targeting specific absorption bands in the MIR region.
Read More: Keisuke Hashimura et al, J. Innov. Opt. Health Sci. 07, 1450029 (2014).
Regards, Leonid Skvortsov
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Hi All,
I need to design an optical solid phantom with defined optical properties. Assuming that I know my required optical properties (including absorption and scattering coefficient and g which in fact are resembling tissue optical properties) how can I find out how much absorbing agent I need to add to the phantom mixture to obtain desired absorption coefficient?
Scattering coefficient could be calculated form Mie theory. Is it used for absorption as well?
Thanks very much,
Amir
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I am very much interested in depth of imaging capabilities of UOT, however I would like to know if there has been efforts to take the spatial resolution from the mm to micron level. (Don't worry I'm not being that lazy - I am actively searching myself but I like the idea of working smarter not harder). If anyone has any leads, please let me know!
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My colleague Robert Dickson in the School of Chemistry and Biochemistry at Georgia Tech is using dual wave length, optically modulated excitation for sensitive  photo acoustic imaging. You might want to contact him for the details.  
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Hi All,
I have a simulation results, which in fact is a finite element mesh showing variation of light intensity at the surface.
Via experiments I have an image taken by a normal camera showing intensity over a surface.
Now I want to correlate these two together, to decide about next set of experiments and simulation, and in short get some useful data. In particular I'm interested to correlate the variation in intensity in simulations and experiments.
What can I do about that?
Any ideas or insights is appreciated.
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Dear Amir,
Let me suggest the following:
1. First, you need to register the two images (Simulated and real).
2. You can do a physical registration and this is through a photogrammetric models such as the collinerity model. Or you can use an approximate geometric model to align the two images.
3. After the alignment you can start comparing the two images using any similarity or dissimilarity measure to evaluate the discrepancy between the two images.
Regards,
Gamal  
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Hi All, 
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.
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Hi Amir,
there is no simple answer to you question since any wavelength interacts with tissue. So if you do not kwow which physical effect you want to study. Diffuse Reflectance is usually due to body scattering. Scattering itselfe is dependent on the wavelength and the size of the targets (and other things, maybe have a look at wikipedia or a textbook). 
You should also consider absoption. If you choose a wavelength that is, e.g. stongly absorbed by water it migth not give you much signal in refectance.
As for the difference between lasers and LED, laser are basically strictly monochromatic, means emitt light with one exact wavelength, LED emitt ligth with an band of wavelengths, means a maximum wavelength and bandwidth.
Hope that gives you some directions.
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Dear All,
Wondering what would be the definition of attenuation and diffusion coefficients, their relationship with blood volume fraction ?
Does the relationship differs case to case (different tissue, and/or experimental setup, etc)? How this relationship could be formulated?
Any insight or introductions to suitable publications is greatly appreciated.
Regards
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Dear Amir,
please note that the scattering coefficient of blood does not scale linearly with the concentration of red blood cells (the hematocrit). Please see e.g. the link to a review paper on the optical properties of blood and references therein.
Best,
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Hallo everyone! Have you any experience about the implementation of inverse Monte Carlo algorithm for the simulation of photon transport through biological tissues and th estimation of optical properties (absorption, scattering and anisotropy coefficients)?
I implemented the algorithm on Matlab, it works, but I have some doubts.
Thank you in advance for you kind attention,
Paola
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I have done a similar work, to simulate the performance of a displacement sensor launching light onto a target and collecting the backreflection (I did a 2nd order Monte Carlo). I found this article useful:
J. C. Ramella-Roman, S. A. Prahl, and S. L. Jacques, “Three Monte Carlo programs of polarized light transport into scattering media: part I,” Optics Express, vol. 13, no. 12, pp. 4420–4438, 2005 (and the subsequent ones)
I think a benchmark can be Zemax or one of the ray tracing softwares available on the market. I'm not sure I can be much help because I don't have expertise in biological tissues.
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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?
Thank you.
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Hi,
Comsol cannot offer you the same accuracy as MC. The reason is obvious: Comsol can solve the diffuse approximation (DA) equation, which is valid only in high scattering media and far enough from the source. On the contrary, MC can provide results more or less equal to the radiation equation if enough photons are used.
Some more links for Comsol and DA:
Best regards
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Hi,
I am looking for an open source Optical-simulator to simulate simple light transmission through a block with specific absorption and scattering coefficients. Can anyone recommend me one, since online search was not very helpful ?
Or if you can suggest some other substitute from your experience. Any help will be highly appreciated.
Thanks
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Hi,
You'll need to provide a lot more information about what you're trying to do. There's a lot of tools out there which can do what you're thinking. It really depends on the problem. If it's very simple, there might be a simple solution. If it's not, it might be solvable using a full maxwell simulation like FDTD (e.g. meep), depending on how "big" the simulation needs to be.  Otherwise, you will need a more specific solution which would depend on the symmetries of the problem and so forth. 
Anyway, if you know what sort of a code you need, this is a pretty good list of online codes which work. It's not perfectly updated but it's a good place to start. 
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I'm wondering if somebody tried to extract a local photon density in a turbid medium from local extinction measurements with gold nanoparticles present in the medium. Let's say that there's a known density of gold nanoparticles present as a localized inclusion and acting as a probe in a certain area inside a turbid medium, and one can measure the extinction (or absorption) values caused by them in this area. Is there a way to estimate the local photon density from such measurements?
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Bernoulli Statistics still apply. The E-field is non-coherent, the energy density is still 1.0000(00). Homogenous distribution is an assumption, the Lagrange invariant still applies. An average Coherence length should still apply.
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The linearly polarized light incident to the tissue gives us different response from the  surface and the bulk in the highly scattering tissues such as dermis, retina, etc.
The reflected light from the surface keeps the same polarization while the light reflected back from the layers in depth undergoes the  multiple scattering that certainly  depolarize the incident light. The de-polariztion ratio may account for the discrimination  of  the  unhealthy  from healthy tissues leading to  the diagnosis of the disease.
The phenomena may contribute to diagnosis  the diabetic retinopathy , dermal disorders and cutaneous and subcutaneous diseases.
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Nishidate et. al has reported a multi-spectral diffuse reflectance imaging method based on a single snap shot of Red-Green-Blue images for estimating melanin concentration, blood concentration, and oxygen saturation in human skin tissue. Multiple regression analysis of the absorbance spectrum and the extinction coefficients of melanin, oxygenated hemoglobin and deoxygenated hemoglobin provides concentrations of melanin and total blood;
Sensors 2013, 13(6), 7902-7915; doi:10.3390/s130607902
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Hi Serge,
There is a sort of a "bible" of myoglobin and hemoglobin in where you will find extinction coefficients and all sorts of other data on both proteins.
Best Signe
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To compare Hydrophobicity of two spectacles lenses
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I would consider using contact angle goinometry with water. As the degree of hydrophobicity increases so will the angle of the water droplet. This method is nondestructive. 
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Dear colleagues,
I'd need to collect NIR light trans-urethrally with an optical fiber. Does anybody know if such optically transparent (~700 nm -900 nm) catheters exist? Can you recommend the company and model, please?
Thanks,
Serge
P.S. In particular, I'd be interested in catheters made from Ultra Clear Silopren LSR 7000 liquid silicone rubber (LSR) if somebody makes them. LSR 700 has ~ a striking 94%  flat transmission in the entire VIS-NIR range!
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Dear Serge, All silicon urethral catheter (foley or nelaton ) are partially transparent. I think for your desired wavelength which ranges through red and infra red,  these catheters satisfy the partial ( and not complete) transparency.
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The classical Beer-Lambert law (BLL) can be applied for extraction of optical properties of a sample (mu_a or mu_extinction in a more general case) under known and controlled illumination & detection conditions as for example in a conventional cuvette spectroscopy. 
For turbid media applications, it has to be modified to account for scattering and increased optical pathlength. So, it transforms to the modified Beer-Lambert law (MBLL). Then, it is usually applied to get information about optical properties of chromophore(s) that are distributed in turbid media. For example, hemoglobin in tissues etc.
Does anybody know if MBLL (or BLL) was applied to obtain optical properties of a localized chromophore inclusion embedded in turbid media? Imagine doing spectroscopic cuvette measurements with the cuvette filled with a certain chromophore and detector embedded in a biological tissue, for example and trying to extract its mu_a. Has anybody tried to adopt MBLL for this purpose by accounting for absorbed and scattered photons?   
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Yes, but instead of the TOTAL average  path length ( <L> =DPF *d) you have to consider the partial average path length in the inclusion <Li> (<Li> =PDPF*d)
where PDPF is the partial differential path length factor. <Li> is the average path length traveled by a DETECTED photon inside a focal region, while <L> is the TOTAL average path length traveled by a DETECTED photon in the medium. The general law is:
Delta-I/Io= -Sum(i=1,n) <Li>Delta-mua(i)
which is valid under ANY situation (the medium does not even to be scattering).
Delta-I/Io is the change of detected intensity normalized to the baseline value, while Delta-mua(i) is the change of the absorption coefficient in the voxel (i). <Li> is the average path length traveled inside that voxel by a detected photon. Try to read (Zheng et al. JBO 15 2010 "Phasor representation of oxy- and deoxyhemoglobin concentrations: what is the meaning of out-of-phase oscillations as measured by near-infrared spectroscopy?"), or "(A. Sassaroli et al. "Perturbation theory for the diffusion equation by use if the moments of the generalized temporal point spread function JOSA A 2006)
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I’d like to set up collaboration with those who have an access to human and/or canine prostates with cancer and might be interested in 1) exploring interstitial optical studies of prostates with cancer for diagnostic purposes and 2) using gold nanoparticles as contrast agents for prostate cancer detection. The goal is two-fold.
First, we want to establish a correlation between concentrations of major chromophores like Hb, HbO2 and H2O and a presence of PC, as well as measure optical absorption and scattering parameters of the organ on ex vivo excised prostates. Since those prostates will be excised anyway we’d like to perform optical measurements on them after excision before they go for some other destructive tests etc. Once this stage is completed and data make sense, we can proceed to a development of an endoscope for performing such measurements in vivo (illumination via rectum, detection via urethra). The approach would be similar to cystoscopy and will utilize a side-firing fiber (or its variation) as a detector and a cylindrical diffuser as the light source.
Second, we would like to target PC biomarkers (like PSMA) in the gland, functionalize gold nanoparticles with appropriate surface agents, deliver Au NPs to the prostate with cancer and detect them with the same technique (illumination via rectum, detection via urethra). This project is more challenging on a number of reasons: 1) preparing Au NPs for targeting PMSA and still protected from RES that can be efficiently accumulated in the gland has never been done (most studies in vitro); 2) since such studies would require working with Au NPs and patients, FDA approval can be an issue. Doing these experiments in dogs would be almost ideal. However, there are conflicting reports on PSMA as a biomarker in canine prostate cancer (see below). Thus, if PSMA can indeed be used and targeted in canine PC, no human prostates would be involved and entire experiments can be performed on canine prostates.
Why not going with rats, for example? Because of the size of the prostate. We really want to go through cm’s of prostate tissue, and dog’s prostate is almost an ideal substitute for a human prostate (sizewise). On the other hand, we’d like to target realistic Au NPs concentrations in the prostate that can be achieved in such studies. So, I’d really like to get your thoughts and possibly practical suggestions on this aspect. I do believe that such molecular imaging of PC via optical detection of Au NPs may not only improve the early cancer detection but pave the way for Au NPs-mediated thermal therapies for focal cancer ablation (but this is a scientist talking:) The nature of this project would require a multidisciplinary team of oncology urologists, molecular biologists, chemists.
We can detect Au NPs in the prostate via urethra using optical radiance technique. Moreover, the sensitivity is much better than the sensitivity of the clinical CT (see the comparison in the publication and relevant references). We can see <=10^10 Au nanorods in the prostate. It means that with saturating of 1-10% of existing PSMA copies per cell ( close to 10^6 sites per cell), detecting 10^10 Au NPs would correspond to seeing ~10^5 malignant cells in the prostate. This number corresponds to the so-called angiogenic switch indicating very promising potential for early cancer detection.
More details on the method are provided in our recent publication (below). I encourage you to read it, and I’d be happy to discuss logistics and answer questions on this topic because there is no way to address all relevant issues in this posting.
Really looking forward for the feedback!
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Let converse.
Best,
Dragan
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I am pursuing research on smart glass- glass with optics embedded in it. I want to try this smart glass first using a functioning model of the eye instead of real eyes. I am looking for such model of an optical eye. Can I put eyeglass on the face with a dummy functioning eye to check whether the smart glass design works or not?
Any input is valuable. I want to add these results to a publication so I am really keen to find optimal solution of setup.
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You can legitimately use a camera as an eye surrogate for testing real/virtual registration in AR.  You will, however, have to model the position of the camera in the same manner you would have to model the position of the eye.  Keep in mind that in optical-see-through AR the combination of real and virtual elements happens (optically) before the light reaches the eye, so if the optical center of the camera is known and is placed in a reasonable eye position, the camera's view of the AR scene should be roughly equivalent to that of forward-looking eye in the same position.  I'm going to try to attach some photos of a setup I did years ago for calibrating real/virtual registration in an OST-AR display.  I hope this is helpful.
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Does it mean that light is particle?
To my knowledge , the light detectors within any spectral range detects light based on photon property of light. The array detector function is also based on photon interaction with sensor. Interference as a significant wave effect of light occurs when it meets the adequate degree of spatial and temporal coherence and does not influence on the photon detection. Diffraction as other main wave effect of light takes place in the slits or periodical structures suitable for spectral resolution, however does not affect on photon detection. Despite, light in resonator performs as a wave , again the stationary or traveling wave formation ( axial and traverse modes in laser cavity) can not influence on photon detection principle. The propagation of light in fiber (LP modes) may be another example that wave characteristics of light contribute to the mode formation, however detection is always based on photon counting.
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@Rasbindu
By  detect I mean mentally respond to the light signal.
Human subjects were placed in a dark room and subjected to small pulses of light. The subjects reported each time they perceived light. The conclusion of the experiment was that humans can see (detect) a single photon of light. Repeats of the experiment confirmed that humans can see less than 10 photons. A pulse of more than 10 photons is necessary for a human to see one photon. Light is lost in the passage through cornea, lens, eye fluid, and the covering of the retina. The conclusion that a single photon was detected (seen, reported) depends on knowing how many photons impinged upon the cornea and knowing (assuming, estimating) how many photons reached a photo-receptor in the cornea. 
Yes. By detect I mean see or the mental experience of the sensation of light.
As Hanno noted my statements referred to the difference between perceiving light and perceiving color. 
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There is an indication (J. H. Ali, W. B. Wang, M. Zevallos and R. R. Alfano, "Near infrared spectroscopy and imaging to probe differences in water content in normal and cancer human prostate tissues," Technol. Cancer Res. Treat. 3, 491-497 (2004)) that cancer tissues may have lower water content in vitro. I'm wondering if somebody done similar studies (in vitro, ex vivo, in vivo). While the prostate is of the main interest, any other organs and tissues would do it as well!
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You may find the water content of tissue in the following publications:
White, D. R., Widdowson, E. M., Woodard, H. Q., & Dickerson, J. W. (1991). The composition of body tissues (II). Fetus to young adult. The British Journal of Radiology, 64(758), 149–59. Retrieved from http://bjr.birjournals.org/content/59/708/1209.short
White, D. R., Woodard, H. Q., & Hammond, S. M. (1987). Average soft-tissue and bone models for use in radiation dosimetry. The British Journal of Radiology, 60(717), 907–13. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/3664185
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I couldn't find much (or anything) on reports of spectrally resolved optical properties (absorption and scattering) of thermally coagulated muscle tissue. So, please share your knowledge on the topic. Human, bovine, porcine, canine - anything would be useful. Any group of muscles will do. Single-wavelength measurements will be useful as well.
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The thesis is very useful. Thank you Mehra.
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I am modelling the oblique incident reflectance profiles using a diffusion model, but would like to examine the range in which it is valid.
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Otto, try online service http://biophotonics.otago.ac.nz/MCOnline.aspx. It might work for you.
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I want to know in terms of degradation. I saw at few places it gets dissolved. Does the dissolvability mean degradation of collagen? What about the fluorescence spectrum? Any reference paper on this?
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Hi, AA is commonly used for extraction of collagen from native tissues. AA is of course good solvent for collagen but this is not equivalent with possibility of degradation. I am also curious if there is problem of degradation of collagen in AA solutions
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I am new to the Optical Bloch Equation (OBE) and because of my background in NMR, I found the approach used by Erwin Hahn in the attached paper very fascinating and easy to follow. It has helped with understanding concepts used in
(1) the Springer Handbooks of Atomic, Molecular, and Optical Physics and
(2) the Atom-Photon Interactions by Claude Cohen-Tannoudji and Gilbert Grynberg.
However, I found out (possibly due to my limited knowledge in this area) that contemporary OBEs are slightly different (in terms of terminology) from OBEs as presented by E.L. Hahn.
Therefore, I would like experts to kindly explain some terms in the attached paper. These terms are 'po' (equivalent to NMR magnetic moment on page 24); the term equivalent to gyromagnetic ratio (on page 24) which is equal to 2po/Planck constant (which also appears before the applied field term in the last equation on page 26); and 'N' and 'g' (in the integrals 2a and 2b on page 26).
I want to know what these four terms stand for in optics and how they can be measured in the laboratory.
I understand that 'N(po)u' is a component of the polarization in the system where 'u' is the Bloch vector in the x direction.
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Dear Michael
The u and v terms in these equations represent the in phase and in quadrature components of the induced polarization (or coherences in the language of density matrices).
If I am interpreting what is written correctly the g function in the integral is there to take into account inhomogeneous broadening effects, not homogeneous broadening like that due to lifetime (T1) or collisional dephasing (T2*). If only these were present than no integral would be needed.
Perhaps the most common example is of inhomogeneous broadening is Doppler broadening due to the Maxwell_Boltzmann distribution of velocities this goes like exp(-mc^2*(omega-omega0)^2/2kT*omega0^2) with a normalization constant that I can never remember. Localized crystal fields in solids can give rise to similar effects.
The T1 and T2 times are usually put in by hand to describe the decay of populations (-w/T1) and the coherences (-u/T2 and -v/T2) respectively as in the equations at the top of page 26.
Best regards
Michael
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It appears from published literature, that an individual Au nanocage produces about an order of magnitude higher absorption cross-section than an individual Au nanorod (considering 750-850 nm spectral range and corresponding dimensions of the nanoparticles). Does anybody know if there was some other shape that can do even better than nanocages? I'm looking for strong dominant absorbers (absorption>>scattering).
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Hi Serge,
Got your point. You are right, the plasmonic resonance of single gold sphere alone is hard to go beyond 600 nm. Maybe dimer (two gold sphere close together) can go well into near infrared since the strong coupling between two gold spheres will red shift the plasmonic resonance. I think the key design point is you design the particle combination so that a dark mode is excited. I guess the dark mode may give you large absorption since it radiate less in principle.
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I'd appreciate any references on the subject. Range: 650-900 nm
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Otto,
Thanks for the reference. I've attempted to collect references that deal with optical properties of porcine muscle tissues in order to compare with our own measurements. The request for the community feedback was in case I've missed something (which is almost always a case!) or anybody could provide some recent data.
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Yes, you can, as far as the spectrum and intensity fit your needs.
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Gold spheres, rods and cages; unconjugated.
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I've found the answer if anybody's interested. Use aqua regia (1:3 mixture of nitric and hydrochloric acids) and a syringe with long (>3 inches) 18 Gauge needles. It cleans the capillaries perfectly and removes all the stain from gold. Since the mixture is highly corrosive, don't use the needle for purposes other than cleaning with aqua regia.
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I am interested in using optical fibers with sharpened tips for detection in biochemical systems. We are coating the tips with metallic films or nanoparticles. I've noticed that groups that make these types of sensors always detect the transmitted light from the tip of the fiber. I am curious whether or not the reflected light could be harnessed to do the same sorts of measurements.
I know the relationship between the light transmittance and reflectance of a metallic-coated tapered optical fiber is not trivial, but is there any reason to believe the light reflectance would not be usable in measuring environmental changes?
Any info on the subject is tremendously helpful, even if it does not directly resolve my question.
Thanks.
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Dear Adam,
I not 100% sure what you are aiming at but lets put it like this: In reflection through the fiber you will either detect elastic (i) or inelastic light scattering (ii).
For case (i) no matter how you will design your sensing principle what you will receive back is a large reflected signal from the fiber termination that will dominate the signal. Since this reflected signal will inevitably contribute to the same single fiber mode, any sensor effects will be small changes on top of this signal. This is inherently unfavourable since the background creates a large shot noise floor. However, no problem for large changes, e.g. induced by a global index change or so.
For case (ii) you will be looking for some red-shifted signal, be it fluorescence or Raman scattering. In any case if you look for a weak signal (sensitive sensing...) you will have to deal with a strong background of inelastic scattering that is created inside the fiber (proportional to fiber length). If the signal you want to detect is large enough then this background will not bother you and you can measure in reflection through a fiber no problem. The background can be overcome though by making use of characteristics of the signal to be detected (people have detected single molecules in reflection through a finer) or by making use of hollow-core fibers. Hope this helps!
Bert