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Establishing the Desired Response
One of the most important performance characteristics of the Piranha XL camera that will
determine the camera's suitability for a specific application is its responsivity and the associated
noise level at the system's maximum line rate and under the desired illumination conditions and
lens configuration.
Responsivity and noise performance can be assessed using a stationary plain white bright target
under bright field illumination; or by using no target for rear bright field illumination.
When evaluating the camera's responsivity and noise performance, it is important that the camera
setup is representative of the system configuration. The setup should meet the following
conditions:
•
The camera is set up for TDI imaging.
The lens is in focus, at the desired magnification, and with the desired aperture.
•
The illumination intensity is equal to that of the Automatic Optical Inspection (AOI) system
•
and is aligned with the camera field of view.
The camera is operated with an exposure time that will allow the maximum line rate of the
•
system to be achieved. The camera's internal line rate generator and exposure control can
be used for a stationary target.
Exposure Control
See the section Camera Control Category in Appendix A for GenICam features associated with this
section and how to use them.
Relevant Features: Exposure Time Source, Exposure Time Selector, Exposure Time
Exposure time determines how long pixels collect photons and accumulate the electrons generated.
The longer the exposure time, the more electrons are accumulated and the greater increase in
response.
The exposure time for each line captured is initiated by the trigger pulse and must be completed
before the next trigger pulse occurs. The camera also requires enough time at the end of the
exposure time in order to transfer the image out of the pixels for analog-to-digital conversion.
Therefore, the exposure time cannot be longer than the period between trigger pulses at the
highest line rate minus 2 µsec for 8 and 12 rows.
The Piranha XL camera uses the GenCP Exposure Time feature as the only means to adjust
exposure time. This ensures that the exposure time period is very stable with respect to the
camera's internal timing. Any variation will become line noise in the image.
When using internal trigger mode, the camera will only accept an exposure time that can be
accommodated within the internal line rate that has been set. When using external trigger mode,
the user must ensure that the exposure time can be accommodated within the maximum line rate
period minus 2 µsec for 8 and 12 rows. If the exposure time is longer than the line rate period,
then some of the trigger pulses will be ignored and the image will appear compressed in the scan
direction.
When evaluating the responsivity of the camera, set the exposure time to the maximum allowable
for the system, minus any margin required for illumination degradation, if applicable. The line rate
26 •
The Piranha XL XDR Camera
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