光波画像計測研究室


Contact
Wakayama University,
Faculty of Systems Engineering,
Dept. of Opto-Mechatronics,
Photomechanics Lab.
930, Sakaedani, Wakayama
640-8510, Japan
Tel.+81-73-457-8176
Fax.+81-73-457-8213
Motoharu FUJIGAKI
E-mail
Subject of research

Development of the measurement method for sub-nanometer displacement and strain distributions

Our method achieved quick non-contact measurement of displacement and strain distributions of the structure in the highest resolution.
Purpose
 To achieve higher quality products, manufacturers in every fields require the method to measure strain distributions in high resolution without contacting. We develop the techniques to realize the method that provides quick and high-accurate results efficiently and we work on its practical application and wide application.
Study Results
  1. We developed the method to almost perfectly remove speckle noise effect of laser. This made it possible to measure displacement distribution in sub-nanometer resolution.
  2. We developed the software to analyze strain distribution from displacement distribution obtained with high accuracy.
  3. Compared with conventional method, this method provides the measurement results in much higher resolution. (sub-nanometer for displacement. 5 microstrain (1Mpa) for strain)

Principle of phase shift digital holography

Displacement can be obtained from phase difference between phases before and after deformations. Phase of 2π indicates displacement in wavelength of light (submicron).

   

Sub-nanometer resolution can be obtained by performing phase analysis in 1/1000 resolution.


Method of averaging phase difference

The average of phase difference is calculated on the complex plane. Intensity is regarded as weight.


Windowed PSDHI

The area with higher intensity provides higher reliability.
   
The method uses the data with higher intensity for every pixel. (Method of averaging phase difference)
   
The data becomes more reliable by increasing the number of divisions. (Errors decrease.)



The effect of speckle is removed and data can be obtained in sub-nanometer resolution.


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