Study of Optical Coherence Theory in Measurement

2014 ◽  
Vol 568-570 ◽  
pp. 71-75
Author(s):  
Shuai Kang ◽  
Guang Yi Luo
Keyword(s):  
Interference Pattern ◽  
High Sensitivity ◽  
Optical Path Difference ◽  
Path Difference ◽  
Optical Coherence ◽  
Interference Effects ◽  
Light Interference ◽  
Light Waves ◽  
Uniform Medium ◽  
Transverse Electromagnetic

Light is a transverse electromagnetic wave, which has the volatility and particles. When light waves are added up in the spatial uniform medium, different conditions will produce interference effects in the meeting area. Optical path difference affects the distribution of the interference pattern directly, and the light interference pattern gives information of phase and amplitude in turn. Due to the measurement precision and extremely high sensitivity of response, the principle of optical coherence has been studied based on measuring the related physical quantity indirectly.

A Spectral Calibration Method in Optical Coherence Tomography Based on Interference Signal with Fixed Optical Path Difference

2018 ◽  
Vol 45 (6) ◽  
pp. 0607005
Author(s):  
王瑄 Wang Xuan ◽  
李中梁 Li Zhongliang ◽  
南楠 Nan Nan ◽  
步扬 Bu Yang ◽  
曾爱军 Zeng Aijun ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Calibration Method ◽  
Optical Path Difference ◽  
Path Difference ◽  
Optical Path ◽  
Interference Signal ◽  
Optical Coherence ◽  
Spectral Calibration

scholarly journals Interference Pattern Representation on the Complex s-Plane

2020 ◽  
Author(s):  
José Trinidad Guillen Bonilla ◽  
Alex Guillen Bonilla ◽  
Mario Alberto García Ramírez ◽  
Gustavo Adolfo Vega Gómez ◽  
Héctor Guillen Bonilla ◽  
...  
Keyword(s):  
Interference Pattern ◽  
Complex Function ◽  
Optical Path Difference ◽  
Path Difference ◽  
Graphical Representations ◽  
Low Coherence ◽  
Sensing Systems ◽  
The Laplace Transform ◽  
Bode Diagram ◽  
Poles And Zeros

In this work, the normalized interference pattern produced by a coherence interferometer system was represented as a complex function. The Laplace transform was applied for the transformation. Poles and zeros were determined from this complex function, and then, its pole-zero map and its Bode diagram were proposed. Both graphical representations were implemented numerically. From our numerical results, pole location and zero location depend on the optical path difference (OPD), while the Bode diagram gives us information about the OPD parameter. Based on the results obtained from the graphical representations, the coherence interferometer systems, the low-coherence interferometer systems, the interferometric sensing systems, and the fiber optic sensors can be analyze on the complex s-plane.

Observation of surface morphology by reflection electron holography

1989 ◽  
Vol 47 ◽  
pp. 536-537
Author(s):  
N. Osakabe ◽  
J. Endo ◽  
T. Matsuda ◽  
A. Tonomura
Keyword(s):  
Phase Shift ◽  
Surface Morphology ◽  
High Sensitivity ◽  
High Energy ◽  
Path Difference ◽  
Transmission Mode ◽  
Electron Holography ◽  
Dynamical Process ◽  
High Vertical Resolution ◽  
Amplification Technique

Progress in microscopy such as STM and TEM-TED has revealed surface structures in atomic dimension. REM has been used for the observation of surface dynamical process and surface morphology. Recently developed reflection electron holography, which employes REM optics to measure the phase shift of reflected electron, has been proved to be effective for the observation of surface morphology in high vertical resolution ≃ 0.01 Å.The key to the high sensitivity of the method is best shown by comparing the phase shift generation by surface topography with that in transmission mode. Difference in refractive index between vacuum and material Vo/2E≃10-4 owes the phase shift in transmission mode as shownn Fig. 1( a). While geometrical path difference is created in reflection mode( Fig. 1(b) ), which is measured interferometrically using high energy electron beam of wavelength ≃0.01 Å. Together with the phase amplification technique , the vertivcal resolution is expected to be ≤0.01 Å in an ideal case.

Peak-to-peak tracking method for measurement of optical path difference: Revisited

Optik ◽  
2015 ◽  
Vol 126 (24) ◽  
pp. 5420-5422
Author(s):  
H.H. Ley ◽  
A. Yahaya ◽  
Y. Munajat
Keyword(s):  
Optical Path Difference ◽  
Path Difference ◽  
Optical Path ◽  
Tracking Method ◽  
Peak Tracking

Ex Vivo assessment of competent strut coverage after coronary stenting by optical coherence tomography

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
R Bhoite ◽  
H Jinnouchi ◽  
F Otsuka ◽  
Y Sato ◽  
A Sakamoto ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Predictive Value ◽  
Ex Vivo ◽  
High Sensitivity ◽  
Optical Coherence ◽  
Cross Sectional ◽  
Neointimal Thickness ◽  
Stent Strut ◽  
Oct Imaging ◽  
Definition Of

Abstract Background In many studies, struts coverage is defined as >0 mm of tissue overlying the stent struts by optical coherence tomography (OCT). However, this definition has never been validated using histology as the “gold standard”. The present study sought to assess the appropriate cut-off value of neointimal thickness of stent strut coverage by OCT using histology. Methods OCT imaging was performed on 39 human coronary arteries with stents from 25 patients at autopsy. A total of 165 cross-sectional images from 46 stents were co-registered with histology. The optimal cut-off value of strut coverage by OCT was determined. Strut coverage by histology was defined as endothelial cells with at least underlying two layers of smooth muscle cells. Considering the resolution of OCT is 10–20 μm, 3 different cut-off values (i.e. at ≥20, ≥40, and ≥60 μm) were assessed. Results A total of 2235 struts were evaluated by histology. Eventually, 1216 struts which were well-matched struts were analyzed in this study. By histology, uncovered struts were observed in 160 struts and covered struts were observed in 1056 struts. The broadly used definition of OCT-coverage which does not consider neointimal thickness yielded a poor specificity of 37.5% and high sensitivity 100%. Of 3 cut-off values, the cut-off value of >40 μm was more accurate as compared to >20 and >60 mm [sensitivity (99.3%), specificity (91.0%), positive predictive value (98.6%), and negative predictive value (95.6%)] Conclusion The most accurate cut-off value was ≥40 μm neointimal thickness by OCT in order to identify stent strut coverage validated by histology. Funding Acknowledgement Type of funding source: None

Optical T-Bench Method for Measurement of Optical Path Difference

1963 ◽  
Vol 1 (6) ◽  
Author(s):  
Francis E. Washer ◽  
Walter R. Darling
Keyword(s):  
Optical Path Difference ◽  
Path Difference ◽  
Optical Path

Thermo-Fluid Design Simulation of Nd3+ POCl3 Transverse Flow Liquid Laser Cavity

2021 ◽  
pp. 1-31
Author(s):  
Vinod Singh ◽  
Gaurav Singhal ◽  
Prabal Talukdar
Keyword(s):  
Refractive Index ◽  
Temperature Gradient ◽  
Flow Rate ◽  
Optical Pumping ◽  
Gain Medium ◽  
Optical Path Difference ◽  
Path Difference ◽  
Transverse Flow ◽  
Optical Path ◽  
Liquid Laser

Abstract CFD based thermal design of a transverse flow optical cavity is carried out for 1 kW Nd3+ POCl3 liquid laser source to investigate temperature and velocity distribution in the optical pumping region of the cavity. Temperature gradient and turbulence both affect the refractive index of the liquid gain medium, which results in optical path difference, divergence and hence, poorer quality of the laser beam. The main purpose of this design is to achieve uniform flow and least temperature gradient in the optical pumping region so that the optical path difference can be minimized and a good beam quality can be achieved. CFD model has been developed for carrying out thermo-fluid simulations for this thermal system and based on these simulations, an optimum geometry of inlet ports along with their position from optical pumping region have been proposed. A user defined function (UDF) is incorporated for the input of spatially varying heat source term in each cell of the optical pumping region of the cavity. Variations in refractive index and optical path difference are estimated from the temperature data using another UDF. Simulation reveals that mass flow rate between 1.5 kg/s to 2.0 kg/s maintains the optical homogeneity of gain medium. Preliminary experiments have been carried out to demonstrate the effect of flow rate on the beam divergence and thereby exhibiting the importance of present simulation work.

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