Hologram interferometry of mechanical deformations 
  
Leif Ek and Klaus Biedermann 
Dept of Physics II and Institute of Optical Research 
The Royal Institute of Technology 
Stockholm 
a. Semi-automatic data extraction and evaluation in hologram inter- 
ferometry 
The interference fringes in a holographic interferogram resulting 
from an object deformation are generally localized in space. The 
displacement vector can be evaluated by using the fringe parallax 
occurring when the direction of observation is changed. In the system 
developed at the Institute of Optical Research [1, 2], a conjugate 
reconstruction beam scans the hologram and the resulting fringe 
motion is recorded in the real image of the object. 
HOLOGRAM 
  
  
  
  
Analysis and experiments showed that the system is capable of inter- 
polating fringes to. 1/100 of a fringe. Three-dimensional displacement 
components could be determined with an accuracy of about 40 nm and 
strain with an accuracy of about 10 ystrain over an observation length 
of about 1 cm. 
b. A TV-speckle vibration interferometer 
A number of TV-systems combined with speckle-interferometers have been 
reported, in part comprising extensive electronic equipment for image