FLIR
LEPTON® Engineering Datasheet
The information contained herein does not contain technology as defined by the EAR, 15 CFR 772, is publicly available,
and therefore, not subject to EAR. NSR (6/14/2018).
Information on this page is subject to change without notice.
Lepton Engineering Datasheet, Document Number: 500-0659-00-09 Rev: 203
20
In automatic FFC, the Lepton camera will automatically perform FFC under the following conditions:
•
At start-up
•
After a specified period of time (default of 3 minutes) has elapsed since the last FFC
•
If the camera temperature has changed by more than a specified value (default of 1.5 Celsius degrees)
since the last FFC
The time trigger and the temperature-change trigger described above are both adjustable parameters via the CCI;
however, the default values are recommended under most operating conditions. Decreasing the temperature or
time interval to FFC more often will provide better radiometric accuracy, but the tradeoff is decrease in useful
camera output and radiometry readings due to the increased occurrence of FFC.
The current FFC state is provided through the telemetry line. There are four FFC states, enumerated below and
illustrated in
1.
FFC not commanded (default):
In this state, Lepton applies by default a set of factory-generated FFC
terms. In automatic FFC mode, this state is generally not seen because Lepton performs automatic
FFC at start-up.
2.
FFC imminent:
The camera only enters this state when it is operating in automatic FFC mode. The
camera enters “FFC imminent” state at a specified number of frames (default of 52 frames
at 26Hz, or
approximately 2 seconds) prior to initiating an automatic FFC. The intent of this status is to warn the
host that an FFC is about to occur.
3.
FFC in progress:
Lepton enters this state when FFC is commanded from the CCI or when automatic
FFC is initiated. The default FFC duration is nominally 23 frames at 26Hz, in which case the camera
integrates 8 frames of output as the basis for the correction (the additional frames are overhead). It is
possible to configure the FFC to integrate fewer or more frames (from 1 to 128 in powers of 2).
Utilizing fewer frames obviously decreases the FFC period (with diminishing returns due to overhead)
whereas utilizing more frames provides greater reduction of spatial noise (also with diminishing
returns due to 1/f noise).
quantifies the benefit. Radiometry readings are invalid during this
state.
4.
FFC complete:
Lepton automatically enters this state whenever a commanded or automatic FFC is
completed.
Lepton also provides an “FFC desired” flag in the telemetry line. The “FFC desired” flag is asserted under the same
conditions that cause automatic FFC when in au
tomatic FFC mode. That is, the “FFC desired” flag is asserted at
start-up, when a specified period (default = 3 minutes) has elapsed since the last FFC, or when the sensor
temperature has changed by a specified value (default = 1.5 Celsius degrees) since the last FFC. In automatic
mode, the camera immediately enters “FFC imminent” state when “FFC desired” is true. In manual FFC mode and
