9 1200 
e 
$ 
LIGHT ; Y em A > 
o 
v 
» 
S 1000 A 
CAMERA 3 p^. A 
oO 
À $ meet \ 
NORMAL £ 
TO X © 
= SURFACE {= 4 600 
^t = = 
u$ 
HB & 700 1 
o 
9 = $ 
S 600 ree 
e 
SURFACE a ë i | | 
8 = Angle of Divergence $400 
y = Angle of Incidence ê \ 
Z 2055700 15° 205 25° 30° 35° 40° 45° 50° 55° 60° 
ANGLE OF INCIDENCE » Ÿ 
  
  
10000 
  
FIGURE 5. Properties of Scotchlite High Gain 
Reflective Sheeting, No. 7610. Amount of 
“light reflected to camera (or gain) depends 
on two quantities defined in Upper Left: 
  
angle of divergence 8, and angle of incidence 
vy. Angle of divergence is angle between ray 
of light striking retroreflective surface and 
  
ray reflected to receiver (camera). ‘Angle of 
incidence is angle between ray of light strik- 
ing retroreflective surface and normal to 
surface. 
  
Return or gain is expressed in terms of 
luminance factor which is defined as ratio 
of strength of return from retroreflective 
surface with respect to that from perfectly 
diffusing white surface of equal size and 
shape. Luminance factor varies both with 
  
angle of incidence and angle of divergence. 
Upper Right shows variation as function of 
  
angle of incidence and Louer Right as function is 213 ! 
01 rli 
of angle of divergence. Use of ring strobe 0.1 GINA Oy 
  
  
  
  
  
  
about camera lens serves to keep angle of ANGLE UF DIVERGENCE 8 
divergence to minimum. 
  
  
  
78