Cavitation (Influence of Free Gas Content) 
From equation (4A) it is apparent that the wave amplitude in 
the hologram plane is essentially a Fourier transform of the wave 
amplitude distribution in the object plane. With appropriate change of 
sign, the process of going from the hologram plane to the image 
plane is just an inverse Fourier transform. 
The evaluation of the image intensity distribution has been 
performed numerically. Thus, by the use of a computer program, 
the influence of hologram size, emulsion signal to noise ratio, and 
many other factors can be studied analytically. The effects of either 
the holographic process or the test facility can be estimated prior to 
the actual physical measurement. The following constants were 
used in the calculations for Figures A2 - A4, 
Z 
1 100.00 mm 
k 
9045/mm 
u 
0.03 mm 
ho 
a oe yee) 
p = 7 (i.e., the limit of integration) 
f = -0.3 mm 
a = 1080 
6 =" \ 4 
A = 4 
As the image focusing distance, Z,5 , is changed from 99.7 mm 
to 100.0 mm and then to 100.3 mm, it can be seen in Figures A2 
through A4 respectively, the focusing property of the hologram. 
When Zs equals 100.0 mm, then the bubble and opaque sphere shape 
are in focus, The light passing through the bubble produces an in- 
terference pattern within the bubble outline. For Z> equal to 
100.3 mm, the bubble shape is no longer in focus, but the apparent 
point source of the light passing through the bubble is in focus. This 
is the distinguishing property of a bubble image in contrast to that 
of an opaque sphere. 
1153 
