Phase measurement errors in acousto-optic processing in the case of various power levels

1998 ◽  
Author(s):  
Leon Jodlowski ◽  
Robert Bobrowicz
Keyword(s):  
Measurement Errors ◽  
Phase Measurement

Interferometry-based measurements of oil-film thickness

2001 ◽  
Vol 215 (3) ◽  
pp. 243-259 ◽  
Author(s):  
O Marklund ◽  
L Gustafsson
Keyword(s):  
Film Thickness ◽  
Measurement Errors ◽  
Phase Measurement ◽  
Elastohydrodynamic Lubrication ◽  
Oil Film ◽  
Interferometric Phase ◽  
Experimental Apparatus ◽  
Colour Parameters ◽  
Computer Based ◽  
The Absolute

Measurement of the thickness of thin lubricant films separating rotating surfaces in elastohydrodynamic experiments presents some challenging problems. The nature of the experimental apparatus inhibits the use of most commonly applied interferometric phase measurement methods. Also the absolute thickness of the separating film must be determined, as opposed to relative distances that would be sufficient in most other measurement scenarios where interferometry methods are used. In this paper, computer-based analysis of interferograms recorded using an elastohydrodynamic lubrication Fitzeu interferometer (a so-called ball-and-disc apparatus) is discussed, the main objective being to extract the absolute oil-film thickness. Intensity based methods (most importantly, calibration look-up procedures where colour parameters from recorded dynamic interferograms are compared with table values corresponding to known film thicknesses, but also a phase measurement approach based on multi-channel interferometry using trichromatic light) are described. A discussion regarding compensation for measurement errors due to the pressure dependence of the refractive index of the lubricant is also included.

Surface Topography Measurement Using Digital Moirè Contouring—Errors and Limitations

1995 ◽  
Vol 209 (4) ◽  
pp. 317-325 ◽  
Author(s):  
C Wykes ◽  
R Morshedizadeh
Keyword(s):  
Surface Topography ◽  
Measurement Errors ◽  
Phase Measurement ◽  
Single View ◽  
Maximum Accuracy ◽  
Wide Range ◽  
Optical Magnification ◽  
Potential Applications ◽  
Digital Moiré

Moiré contouring is a technique that enables the surface topography of an object to be measured in a single view and has a wide range of potential applications in manufacturing. However, to be useful, it is necessary to be able to calibrate the system and establish the traceability of the calibration. In this paper, the factors that determine the accuracy of the technique are identified, methods of calibration proposed and attainable accuracies estimated. These include the optical magnification, phase measurement and sensitivity, all of which contribute to measurement errors in the technique. The methods are illustrated with results from a digital moiré system, and the improvements required to obtain maximum accuracy are outlined.

scholarly journals Phase measurement errors due to holographic interferograms compression

2007 ◽  
Author(s):  
Emmanouil Darakis ◽  
Vijay Raj Singh ◽  
Anand K. Asundi ◽  
John J. Soraghan
Keyword(s):  
Measurement Errors ◽  
Phase Measurement

scholarly journals Analysis of Phase Evaluation Algorithms in an Interferometric Method for Static Deformation Measurement

10.14311/372 ◽  
2002 ◽  
Vol 42 (4) ◽  
Author(s):  
J. Novák
Keyword(s):  
Measurement Errors ◽  
Complex Analysis ◽  
Phase Measurement ◽  
Evaluation Process ◽  
Surface Shape ◽  
Interferometric Method ◽  
Phase Calculation ◽  
Calculation Algorithms ◽  
Negative Effect ◽  
Measurement And Evaluation

This article describes and analyses an interferometric method for measuring displacements and deformation. The method can be used for a very accurate evaluation of the change in the surface shape of structures used in industry. The paper proposes several multistep phase calculation algorithms and describes an automatic evaluation process using the measurement technique. A complex analysis is also performed of various factors that can have a negative effect on the practical measurement and evaluation process. An analysis is made of the proposed multistep phase calculation algorithms using the proposed error model. It is shown that the resulting phase measurement errors can be effectively reduced by using suitable phase calculation algorithms. The analysis can be applied for a complex comparison of the accuracy and stability of such algorithms.

Analysis of Phase Measurement Errors in Electro-Optic Holography

2001 ◽  
Vol 8 (1) ◽  
pp. 26-31 ◽  
Author(s):  
Sung-Hoon Baik ◽  
Seung-Kyu Park ◽  
Cheol-Jung Kim ◽  
Soo-Yong Kim
Keyword(s):  
Measurement Errors ◽  
Phase Measurement ◽  
Electro Optic

Performance and applications of the holography electron microscope

1993 ◽  
Vol 51 ◽  
pp. 1078-1079
Author(s):  
Akira Tonomura
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Phase Measurement ◽  
Electron Holography ◽  
Imaging Method ◽  
High Contrast ◽  
Magnetic Lens ◽  
High Brightness ◽  
Holographic Imaging ◽  
Dynamic Observation

Electron holography is a two-step imaging method. However, the ultimate performance of holographic imaging is mainly determined by the brightness of the electron beam used in the hologram-formation process. In our 350kV holography electron microscope (see Fig. 1), the decrease in the inherently high brightness of field-emitted electrons is minimized by superposing a magnetic lens in the gun, for a resulting value of 2 × 109 A/cm2 sr. This high brightness has lead to the following distinguished features. The minimum spacing (d) of carrier fringes is d = 0.09 Å, thus allowing a reconstructed image with a resolution, at least in principle, as high as 3d=0.3 Å. The precision in phase measurement can be as high as 2π/100, since the position of fringes can be known precisely from a high-contrast hologram formed under highly collimated illumination. Dynamic observation becomes possible because the current density is high.

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