User`s manual
Spyder 3 GigE User’s Manual
DALSA 03-032-10158-09
41
The focal point is the point at which the image of an infinitely distant object is brought to
focus. The effective focal length (f
′
) is the distance from the second principal point to the
second focal point. The back focal length (BFL) is the distance from the image side of the
lens surface to the second focal point. The object distance (OD) is the distance from the first
principal point to the object.
Figure 19: Primary Points in a Lens System
Magnification and Resolution
The magnification of a lens is the ratio of the image size to the object size:
m
h
h
=
′
where m is the magnification, h’ is the image height
(pixel size) and h is the object height (desired object
resolution size).
By similar triangles, the magnification is alternatively given by:
m
f
OD
=
′
These equations can be combined to give their most useful form:
′
=
′
h
h
f
OD
This is the governing equation for many object and
image plane parameters.
Example: An acquisition system has a 512 x 512 element, 10m pixel pitch area scan
camera, a lens with an effective focal length of 45mm, and requires that 100μm in the
object space correspond to each pixel in the image sensor. Using the preceding equation,
the object distance must be 450mm (0.450m).
10
100
45
450 0 450
μ
μ
m
m
mm
OD
OD mm m==(. )
4.3 Electrical Interface
The Spyder 3 GigE cameras have been designed for EMC compliance. The test setup has
been verified to the following EMC standards:
• CISPR-11:2004
• EN 55011:2003
• EN 61326:2002
To achieve EMC compliance, follow these specific guidelines: