Dalsa PC-30-02K80-R Manual page 73

Piranha Color Camera User's Manual
Figure 10: Primary Points in a Lens System
OBJECT
HEIGHT (h)
Magnification and Resolution
The magnification of a lens is the ratio of the image size to the object size:
m = h ' h
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
Example: An acquisition system has a 512 x 512 element, 10µm 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 µm
—
100 µm
DALSA
LIGHT RAYS FROM LEFT
FIRST PRINCIPAL
POINT
OPTICAL AXIS
OBJECT
DISTANCE (OD)
OBJECT SIDE
where m is the magnification, h' is the image height
—
(pixel size) and h is the object height (desired object
resolution size).
= f '
This is the governing equation for many object and
—
OD
image plane parameters.
45 mm
= — OD=450 mm (0.450 m)
OD
03-032-10211-03
SECOND PRINCIPAL POINT
SECOND FOCAL POINT
BACK FOCAL LENGTH.
f
IMAGE SIDE
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9/27/2007