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