scholarly journals Parametric Study to Improve Subpixel Accuracy of Nitric Oxide Tagging Velocimetry with Image Preprocessing

2017 ◽  
Vol 2017 ◽  
pp. 1-17
Author(s):  
Ravi Teja Vedula ◽  
Mayank Mittal ◽  
Harold Schock
Keyword(s):  
Line Width ◽  
Signal To Noise Ratio ◽  
Laser Line ◽  
Image Preprocessing ◽  
Molecular Tagging Velocimetry ◽  
Displacement Error ◽  
Air Jet ◽  
Subpixel Accuracy ◽  
Filter Size ◽  
Laser Line Width

Biacetyl phosphorescence has been the commonly used molecular tagging velocimetry (MTV) technique to investigate in-cylinder flow evolution and cycle-to-cycle variations in an optical engine. As the phosphorescence of biacetyl tracer deteriorates in the presence of oxygen, nitrogen was adopted as the working medium in the past. Recently, nitrous oxide MTV technique was employed to measure the velocity profile of an air jet. The authors here plan to investigate the potential application of this technique for engine flow studies. A possible experimental setup for this task indicated different permutations of image signal-to-noise ratio (SNR) and laser line width. In the current work, a numerical analysis is performed to study the effect of these two factors on displacement error in MTV image processing. Also, several image filtering techniques were evaluated and the performance of selected filters was analyzed in terms of enhancing the image quality and minimizing displacement errors. The flow displacement error without image preprocessing was observed to be inversely proportional to SNR and directly proportional to laser line width. The mean filter resulted in the smallest errors for line widths smaller than 9 pixels. The effect of filter size on subpixel accuracy showed that error levels increased as the filter size increased.

scholarly journals Absorption spectroscopy of trapped rubidium atoms

2004 ◽  
Vol 82 (11) ◽  
pp. 905-916 ◽  
Author(s):  
S Cauchi ◽  
A Vorozcovs ◽  
M Weel ◽  
S Beattie ◽  
O Gagnon ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Line Width ◽  
Optical Pumping ◽  
Laser Line ◽  
Trapped Atoms ◽  
Rubidium Atoms ◽  
Fabry Perot ◽  
Measured Absorption ◽  
High Finesse ◽  
Laser Line Width

We determine the absolute density of a sample of laser-cooled atoms in a two-level system by recording the absorption spectrum of the 85Rb 5S1/2 (F = 3, mf = 3) → 5P3/2 (F′ = 4, m′f = 4) transition. Trapped atoms were prepared in the (F = 3, mf = 3) ground state through optical-pumping techniques. We compare our results with an independent measure of the density that relies on a direct measurement of the number of atoms and size of the atomic sample. We also study the contributions of power broadening, laser line width, and Doppler broadening to the measured absorption spectrum. Our studies suggest that the natural line width (~6 MHz) can be measured to a precision of less than ~50 kHz if the laser line width is measured in real-time with a high-finesse Fabry–Perot cavity. PACS Nos.: 32.70.Cs, 32.70.Jz, 32.80.Pj, 42.62.Fi, 32.70.–n, 32.30.–r

scholarly journals Errors reducing method of Laser 3D scanner

2014 ◽  
Vol 17 (1) ◽  
pp. 43-49
Author(s):  
Lam Huynh Phan ◽  
Nam Thanh Nguyen ◽  
Duy Van Pham
Keyword(s):  
Line Width ◽  
Camera Calibration ◽  
Laser Light ◽  
Focal Length ◽  
Laser Line ◽  
3D Scanner ◽  
Surface Motion ◽  
Laser Line Width

This paper presents the factors that influence the form scanning processing by using the laser: light ambient, scanning surface, motion axial, focal length of the camera. This paper will present the method to reduce the error of the environment by using the camera calibration algorithms and the coordinate movements. This errors reducing method to solve the problem from local to genera: from solving errors created by the curve of the cameras to the laser-line width, to the dark gray threshold of the images by the camera aperture and coupling 2- movement axis to scanning-coupling more effectively.

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