Building Earth Observation Cameras

29Image Formation

Before we proceed further, it is useful to familiarize with the concept of

contrast ratio. The difference in radiance of the objects in a scene plays an

important role in their detection.

The contrast is usually referred with respect to two adjacent areas. If L

max

and L

min

are the maximum and minimum radiance between adjacent areas

(Figure 2.13), the contrast ratio C

R

is given by

C

L

L

=

R

max

min

(2.11)

The contrast modulation (modulation depth) C

M

is given by

C

LL

LL

=

−

+



M

ma

xm

in

maxmin

(2.12)

where L

max

and L

min

are the maximum and minimum values of the exitance

(irradiance) of the white and black targets at the object (image) space. The ...