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
·
