Dalsa Piranha ES-80-08k40-00-R User Manual page 86

86
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Filters
CCD cam eras are extrem ely responsive to infrared (IR) w avelengths of light. To prevent
infrared from d istorting the im ages you scan, u se a ―hot m irror ‖ or IR cu toff filter that
transm its visible w avelengths bu t d oes not transm it w avelengths over 750nm . Exam ples
are the Schneid er Optics™ B+W 489, w hich inclu d es a m ou nting ring, the CORION ™ LS-
750, w hich d oes not inclu d e a m ou nting ring, and the CORION ™ H R-750 series hot
m irror.
Lens Modeling
Any lens su rrou nd ed by air can be m od eled for cam era pu rposes u sing three prim ary
points: the first and second principal points and the second focal point. The prim ary
points for a lens shou ld be available from the lens d ata sheet or from the lens
m anu factu rer. Prim ed qu antities d enote characteristics of the im age sid e of the lens. That
is, h is the object height and h
The focal point is the point at w hich the im age of an infinitely d istant object is brou ght to
focu s. The effective focal length (f
second focal point. The back focal length (BFL) is the d istance from the im age sid e of the
lens su rface to the second focal point. The object distance (OD) is the d istance from the first
principal point to the object.
Figure 27: Primary Points in a Lens System
03-032-20070-02
Som e light sou rces age; over their life span they prod u ce less light. This aging m ay
not be u niform —a light sou rce m ay prod u ce progressively less light in som e areas of
the spectru m bu t not others.

is the im age height.
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) is the d istance from the second principal point to the
Piranha ES-xx User Manual
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