Distant-detector versus integrating sphere measurements for estimating tissue optical parameters: A comparative experimental study

Optik ◽  
2021 ◽  
Vol 247 ◽  
pp. 167981 ◽  
Author(s):  
Omnia Hamdy ◽  
Nahed H. Solouma
Author(s):  
Norio Baba ◽  
Norihiko Ichise ◽  
Syunya Watanabe

The tilted beam illumination method is used to improve the resolution comparing with the axial illumination mode. Using this advantage, a restoration method of several tilted beam images covering the full azimuthal range was proposed by Saxton, and experimentally examined. To make this technique more reliable it seems that some practical problems still remain. In this report the restoration was attempted and the problems were considered. In our study, four problems were pointed out for the experiment of the restoration. (1) Accurate beam tilt adjustment to fit the incident beam to the coma-free axis for the symmetrical beam tilting over the full azimuthal range. (2) Accurate measurements of the optical parameters which are necessary to design the restoration filter. Even if the spherical aberration coefficient Cs is known with accuracy and the axial astigmatism is sufficiently compensated, at least the defocus value must be measured. (3) Accurate alignment of the tilt-azimuth series images.


2013 ◽  
Author(s):  
Christoph Böcklin ◽  
Dirk Baumann ◽  
Florian Stuker ◽  
Jan Klohs ◽  
Markus Rudin ◽  
...  

Optik ◽  
2017 ◽  
Vol 140 ◽  
pp. 1004-1009 ◽  
Author(s):  
Omnia Hamdy ◽  
Mahmoud Fathy ◽  
Tarek A. Al-Saeed ◽  
Jala El-Azab ◽  
Nahed H. Solouma

2016 ◽  
Vol 55 (8) ◽  
pp. 2079 ◽  
Author(s):  
Xiaohui Liang ◽  
Meihua Li ◽  
Jun Q. Lu ◽  
Chuanwei Huang ◽  
Yuanming Feng ◽  
...  

2019 ◽  
Vol 25 (1) ◽  
pp. 1-5
Author(s):  
Habib E. Ashoor ◽  
Khalil Ebrahim Jasim

Abstract The behaviour of light interaction with biological tissue is determined by micro-optical parameters: refractive index (n), absorption coefficient (µa), scattering coefficient (µs), and anisotropy (g). The goal of this study is to measure the optical properties of normal whole blood using He-Ne laser (wavelength 632.8 nm). The refractive index is measured using the traveller microscope. The integrating sphere method is used to measure the macro-optical parameters: total diffusive reflectance, transmittance, and collimated transmittance at wavelength 632.8 nm. The macro-optical parameters are fed to Inverse Adding Doubling (IAD) theoretical technique, to estimate the micro-optical parameters (µs, µa, g). An alternative practical method is used to measure the g value based on utilising the goniometric table. The study reveals that the refractive index (n) equals 1.395±0.0547, absorption coefficient (µa) equals 2.37 mm−1, scattering coefficient (µs) equals 55.69 mm−1, and anisotropy (g) equals 0.82. In conclusion, these findings approved, in general, the applicability of the suggested experimental set up. The set up depend on using three devices: the integrating sphere method to estimate (µs, µa, g), traveller microscope (n) and goniometer (g).


Crystals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 203
Author(s):  
Zhili Zhao ◽  
Xinzhong Wang ◽  
Kaidong Yang ◽  
Fang Fan ◽  
Dan Wu ◽  
...  

Optical performance in terms of light efficiency, color crosstalk and ambient contrast ratio were analyzed for blue GaN-based micro-light emitting diodes (micro-LEDs) combined with red/green quantum dots (QDs)-polymethyl methacrylate (PMMA) films. The thickness and mass ratio of QDs films are two critical factors in affecting the performance of micro-LEDs. Firstly, the precise optical modeling of QDs-PMMA films is established based on the double integrating sphere (DIS) testing system and inverse adding doubling algorithm (IADA) theory. Red and green QDs-PMMA films are composed of ZnCdSe/ZnS QDs and green ZnCdSeS/ZnS QDs, respectively. The fundamental optical parameters of QDs-PMMA films, including scattering, absorption and anisotropy coefficients, are obtained successfully. Secondly, based on these optical parameters, the Monte Carlo ray tracing method is applied to analyze the effect of a QDs-PMMA film’s thickness and mass ratio on the optical performance of micro-LEDs. Results reveal that the light efficiency first increases and then decreases with the increase of a QDs film’s thickness or mass ratio, owing to the scattering characteristics of QDs. Different from the variation tendencies of light efficiency, the crosstalk between adjacent pixels increases as the QDs-PMMA film’s thickness or mass ratio increases, and the ambient contrast ratio is kept stable when the thickness increases. The mass ratio variation of QDs film can change the optical performance of micro-LEDs more effectively than thickness, which demonstrates that mass ratio is a more important factor affecting the optical performance of micro-LEDs.


Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 423
Author(s):  
Paulina Listewnik ◽  
Monika Ronowska ◽  
Michał Wąsowicz ◽  
Valery V. Tuchin ◽  
Małgorzata Szczerska

Optical phantoms are used to validate optical measurement methods. The stability of their optical parameters over time allows them to be used and stored over long-term periods, while maintaining their optical parameters. The aim of the presented research was to investigate the stability of fabricated porous phantoms, which can be used as a lung phantom in optical system. Measurements were performed in multiple series with an interval of 6 months, recreating the same conditions and using the same measuring system consisting of an integrating sphere, a coherent light source with a wavelength of 635 nm and a detector. Scattering and absorption parameters were determined on the basis of the measured reflectance and transmittance. The tested samples were made of silicone and glycerol in various proportions.


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