Dalsa Piranha 3 P3-80-08k40-00-R, Руководство пользователя

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Piranha 3 User Manual
Teledyne DALSA 03-032-10216-06
65
4.2 Optical Interface
Illumination
The am ou nt and w avelengths of light requ ired to cap tu re u sefu l im ages d ep end on the
p articu lar ap p lication. Factors inclu d e the natu re, sp eed , and sp ectral characteristics of
objects being im aged , exp osu re tim es, light sou rce characteristics, environm ental and
acqu isition system sp ecifics, and m ore. Teled yne DALSA’s Web site,
here , p rovid es an
introd u ction to this p otentially com p licated issu e. See ―Rad iom etry and Photo
Responsivity‖ and "Sensitivities in Photometric Units" in the CCD Technology Primer
fou nd u nd er the Ap p lication Su p p ort link.
It is often m ore im p ortant to consid er exp osu re than illu m ination. The total am ou nt of
energy (w hich is related to the total nu m ber of p hotons reaching the sensor) is m ore
im p ortant than the rate at w hich it arrives. For exam p le, 5

J/ cm
2
can be achieved by
exp osing 5m W/ cm
2
for 1m s ju st the sam e as exp osing an intensity of 5W/ cm
2
for 1

s.
Light Sources
Keep these gu id elines in m ind w hen setting u p you r light sou rce:
• LED light sources are relatively inexpensive, provide a uniform field, and longer life
sp an com p ared to other light sou rces. H ow ever, they also requ ire a cam era w ith
excellent sensitivity, su ch as the Piranha 3 cam eras.
• Halogen light sources generally provide very little blue relative to IR.
• Fiber-optic light distribution systems generally transmit very little blue relative to IR.
• Some light sources age; over their life span they produce less light. This aging may
not be u niform —a light sou rce m ay p rod u ce p rogressively less light in som e areas of
the sp ectru m bu t not others.
Filters
CCD cam eras are extrem ely resp onsive to infrared (IR) w avelengths of light. To p revent
infrared from distorting the images you scan, use a ―hot mirror ‖ or IR cutoff filter that
transm its visible w avelengths bu t d oes not transm it w avelengths over 750nm . Exam p les
are the Schneider Optics™ B+W 489, which includes a mounting ring, the CORION™ LS-
750, which does not include a mounting ring, and the CORION™ HR-750 series hot
m irror.
Lens Modeling
Any lens su rrou nd ed by air can be m od eled for cam era p u rp oses u sing three p rim ary
p oints: the first and second p rincip al p oints and the second focal p oint. The p rim ary
p oints 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

is the im age height.
The focal point is the p oint at w hich the im age of an infinitely d istant object is brou ght to
focu s. The effective focal length (f

) is the d istance from the second p rincip al p oint to the
second focal p oint. The back focal length (BFL) is the d istance from the im age sid e of the
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