Optical Considerations; Illumination; Light Sources; Filters - Genie M640 User Manual

Optical Considerations

This section provides an overview to illumination, light sources, filters, lens modeling, and lens magnification. Each
of these components contribute to the successful design of an imaging solution.

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. The DALSA Web site,
http://vfm.dalsa.com/, provides an introduction to this potentially complicated issue. Click on the Application
Support link and then select the CCD Technology Primer. Review "Radiometry and Photo Responsivity" along
with other sections of interest.
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,
2
5μJ/cm can be achieved by exposing 5mW/cm

Light Sources

Keep these guidelines in mind when selecting and setting up 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.
•
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 such that 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

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.
Genie Monochrome Series-GigE Vision Camera
2
for 1ms just the same as exposing an intensity of 5W/cm
2
for 1μs.
Technical Specifications • 101