3 P~ H* P rt Hi H' 
(D (i rt fL (t 3 
p *<i p* o p 
rt • (D hh P 
• rt 
PPM 
a. p 
Pu p 
P H-* 
t*l !> rt 
P rt 
a. 
p p *• 
P OQ P p M 
M M 
• rt €3 
p p 
P M 
rt T3 
p t 
rt 
H* 
o 
3 
p 4 p p 
P M 
Figure I. Line diagram of the 
apparatus. The target hole is 
cut in the aluminium sheet T. 
The micrometers and Y move 
the measuring mark inside the 
hole via the Y-primary and 
X-secondary slides as shown. 
The target is illuminated 
from below, and the total 
length of the reflected light 
path is 6 meters.