Image Processing Reference

In-Depth Information

Fig. 2.7
Different focal

lengths results in optical

zoom

Fig. 2.8
A focused image

(
left
) and an unfocused image

(
right
). The difference

between the two images is

different values of
b

A smaller depth-of-field can be achieved by increasing the focal length. However,

this has the consequence that the area of the world observable to the camera is

reduced. The observable area is expressed by the angle
V
in Fig.
2.10
and denoted

the
field-of-view
of the camera. The field-of-view depends, besides the focal length,

also on the physical size of the image sensor. Often the sensor is rectangular rather

than square and from this follows that a camera has a field-of-view in both the

horizontal and vertical direction denoted FOV
x
and FOV
y
, respectively. Based on

right-angled triangles, see Appendix B, these are calculated as

tan
−
1
width of sensor
/
2

f

FOV
x
=

2

·

(2.4)

tan
−
1
height of sensor
/
2

f

FOV
y
=

2

·