]
[
1
]
[
mm
Size
Sensor
B
A
mm
Length
+
=
Focal
A: Distance from lens to object in mm
B: Object size in mm
C: Number of horizontal pixels
D: Number of vertical pixels
14
600
800
014
,
0
]
mm
[
Size
Sensor
2
2
=
+
⋅
=
Example:
C: Number of horizontal pixels = 800
D: Number of vertical pixels = 600
A: Distance from lens to object = 300 mm
B: Object size = 100 mm
calculated focal length = (300 : (1 + (100 : 14))) = 36,8 mm
when a lens with focal length of 35 mm has to be used, and the object size
has to be kept at 100 mm, the distance from lens to object has to be
changed as follows:
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
+
⋅
=
Size
Sensor
Size
Object
Length
Focal
mm
Object
to
1
]
[
Distance
at a focal length of 35mm, an object size of 100mm and a sensor size of
14mm the new distance from lens to object is calculated as:
35
⋅
(1 + (100 : 14)) = 285 mm
The distance from lens to object has to be reduced from 300mm to
285mm
Vice versa, when the distance from lens to object has to be reduced, the
focus of the lens will come to its limit. and the required magnification factor
CR Series
Ref. 1830-SU-02-G
Page 44
