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22
EC-11User’s
Manual
03-32-00418-05
DALSA
Corp.
3.2 Optical Interface
The cameras come with a built in C-mount lens adapter for the 512 and 1024 models. A
built in F-mount adapter is provided on the 2048 model. Both adapters have the
appropriate back focal distance for the lens types being used. Ensure that the image circle
diameter of the lens to be used is as great as the length of the imaging region of the image
sensor.
Illumination
The amount and wavelengths of light required to capture useful images depend on the
particular application. Factors include the nature, speed, and spectral characteristics of
objects being imaged, exposure times, light source characteristics, environmental and
acquisition system specifics, and more. DALSA’s current Databook provides an
introduction to this potentially complicated issue. See “Radiometry and Photo
Responsivity” and "Sensitivities in Photometric Units" in the CCD Technology Primer
chapter.
It is often more important to consider exposure than illumination. The total amount of
energy (which is related to the total number of photons reaching the sensor) is more
important than the rate at which it arrives. For example, 5
µ
J/cm
2
can be achieved by
exposing 5mW/cm
2
for 1ms just the same as exposing an intensity of 5W/cm
2
for 1
µ
s.
Light Sources
Keep these guidelines in mind when setting up your light source.
•
LED light sources are relatively inexpensive, provide a uniform field, and longer
lifespan compared to other light sources. However, they also require a camera with
excellent sensitivity, such as DALSA’s Eclipse camera.
•
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 lifespan they produce less light. This aging may not
be uniform—a light source may produce progressively less light in some areas of the
spectrum but not others.
Filters
CCD cameras are extremely responsive to infrared (IR) wavelengths of light. To prevent
infrared from distorting the images you scan, use a “hot mirror” or IR cutoff filter that
transmits visible wavelengths but does not transmit wavelengths over 750nm. Examples
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
mirror.
Lens Modeling
Any lens surrounded by air can be modeled for camera purposes using three primary
points: the first and second principal points and the second focal point. The primary
Summary of Contents for EC-11-xxx40
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