example of a requirement which is parallel with 
requirements in photogrammetric analysis. 
The example given above is only one of many procedures 
in which holography has been employed in industry. 
These, and other applications of coherent optics in 
measurement are categorised in Reference 2. 
References 
1 Burch.J M "Holographic Measurement of Displacement 
and Strain — An Introduction" 
J Strain Analaysis, 1974, 9, No 1, 
pp 1-3. 
2 Burch J M "Outlines of Optical Metrology" in 
"Engineering Uses of Coherent Optics" 
pp 1-22 Cambridge University Press 1976. 
2 EXPERIMENTAL MEASUREMENT OF NORMAL SURFACE 
DISPLACEMENT BY HOLOGRAPHY 
E Archbold, A E Ennos (3,4) 
An example of the type of problem in the measurement 
of deformation by holography is shown in Figure 1. 
Two plastic pipes are joined by fusing into an 
encircling sleeves The elastic deformation and 
relaxation when the pressure within the assembly is 
changed can be very conveniently observed by 
holographic methods, but to ensure a high sensitivity 
and to simplify quantitative evaluation of the 
patterns it is necessary to choose the directions of 
illumination and viewing properly. As shown in the 
figure, both these directions were made to lie as 
close as possible to the normal to the nearest part 
of the surface. 
   
  
lilumination 
Viewing 
Figure 1 Plastic pipe joint mounted on Vee-blocks 
The real-time ('"live-fringe") method of observation 
with a single recorded hologram was employed as a 
convenient way to establish the directions of 
_ displacement in relation to the directions of 
movement of the fringe pattern, for the purpose of 
assigning fringe order numbers, as described in the 
last section. The double exposure method ("frozen 
fringe") was then used for detailed measurement. 
  
Figure 2 
Photograph of reconstruction from double- 
exposure holograms of the pipe joint 
= + 
: / 
3 ] 
o 
8 4 
£ 
E / 
  
  
  
Distance along pipe joint x—e 
Figure 3 Profile change along surface generator AB 
Figure 2 shows a typical reconstructed interference 
pattern from a "frozen fringe" hologram and Figure 3 
shows the derived profile change along the surface. 
Another typical example is shown in Figure 4. 
    
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Figure 4 
Experimental arrangement to record the 
surfaces of the chair.