| Experienced thermographers
know that image clarity is one of the most important
considerations in thermal imaging. For thermal imagers,
imager frame rate is an important characteristic that
can greatly influence image quality.
Frame rate or frequency describes the
rate at which an imaging device produces unique consecutive
images or frames per unit of time. Until recently, most
NTSC compatible thermal imagers produced 30 to 60 video
frames per second. This frequency provided imagery that
was considered ‘real-time’.
Thermal imagers that have real-time
frame rates permit imaging of either slow moving targets
or imaging of targets while the imager is in motion.
Examples include infrared inspections where the imager
is panned across the face of large targets such as buildings
or where the imager is hand carried such as during walkover
inspections of a flat roof.
For a variety of reasons, many modern
imagers are now manufactured with frame rates of less
than 30 frames per second. When using an imager that
produces less than 30 frames per second, a thermographer
will notice ‘ghost trails’ or image smearing
should either the imager or target be in motion. This
condition will worsen as lower frame rates are encountered.
Clear imagery is possible with imagers
having a slow frame rate; however, both the target and
imager must remain motionless in order to eliminate
image smearing. For some imagers, it may take several
seconds for the image to become clear. Because of this,
slow frame rate imagers may not be suitable for inspecting
expansive targets or targets that are constantly in
motion.
Because frame rate cannot be changed
for any imager, this feature must be considered at the
time of imager selection and/or purchase. Prior to purchasing
any new thermal imager, be certain to try the equipment
under the same conditions that you will likely encounter
in the future to ensure that the frame rate is adequate.
Equipment selection and use are
two of the many topics covered in the
Level I Infraspection Institute Certified Infrared Thermographer®
training course. For information on thermographer training
including course locations and dates, visit us online
at www.infraspection.com
or call us at 609-239-4788.
Visit
Infraspection Institute Web Site |
