Piranha 3 User Manual
03-032-10216-06
Teledyne DALSA
66
lens su rface to the second focal p oint. The
object distance (OD)
is the d istance from the first
p rincip al p oint to the object.
Figure 20: Primary Points in a Lens System
Magnification and Resolution
The m agnification of a lens is the ratio of the im age size to the object size:
m
h
h
where m is the magnification, h’ is the image height
(p ixel size) and h is the object height (d esired o bject
resolu tion size).
By sim ilar triangles, the m agnification is alternatively given by:
m
f
OD
These equ ations can be com bined to give their m ost u sefu l form :
h
h
f
OD
This is the governing equ ation for m any object and
im age p lane p aram eters.
Example:
An acqu isition system has a 512 x 512 elem ent, 10
m p ixel p itch area scan cam era,
a lens w ith an effective focal length of 45m m , and requ ires that 100
m in the object sp ace
corresp ond to each p ixel in the im age sensor. Using the p reced ing equ ation, the object
d istance m u st be 450m m (0.450m ).
10
100
45
450
0 450
m
m
mm
OD
OD
mm
m
( .
)
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