Piranha HN RoHS User Manual
03-032-20135-00
Teledyne DALSA
16
Lens Mounts
Model Number
Lens Mount Options
HN-80
M72x0.75 thread.
Optical Interface
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.
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 life span compared to
other light sources. However, they also require a camera with excellent sensitivity, such as the HN-xx
camera.
Halogen light sources generally provide very little blue relative to infrared light (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 uniform—a
light source may produce progressively less light in some areas of the spectrum but not others.
Filters
In visible light applications, 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.
In NIR imaging applications, a visible light cutoff filter is recommended.
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 points for a lens should be available
from the lens data sheet or from the lens manufacturer. Primed quantities denote characteristics of the
image side of the lens. That is,
h
is the object height and
h
′
is the image height.
The
focal point
is the point at which the image of an infinitely distant object is brought to focus. The
effective focal length (f
′
)
is the distance from the second principal point to the second focal point. The
back
focal length (BFL)
is the distance from the image side of the lens surface to the second focal point. The
object distance (OD)
is the distance from the first principal point to the object.
