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
63
are unchanged. However, it is worth noting a single packet represented a single 80-pixel video line for
Lepton whereas it represents half of a 160-pixel video line in Lepton 3.
3)
The synchronization requirements are identical with one exception. To maintain synchronization, Lepton
requires each video frame to be read out prior to the next available frame. In contrast, Lepton 3 requires
each
segment
to be read out prior to the next available segment, where a segment represents one-
quarter of a video frame. Lepton 3 sync pulse cannot be used to synchronize external circuitry to frames.
4)
For both Lepton and Lepton 3, each unique video frame is followed by two non-unique frames which
must be read out to maintain synchronization. For Lepton each unique video frame is duplicated twice.
For Lepton 3 each unique frame is followed by two partial, invalid frames.
The four most significant differences between the Lepton VoSPI interface and that for Lepton 3 are:
1)
For Lepton, reconstructing a video frame from the individual packets requires the host to decode the
packet number from each packet header. For Lepton 3, the host must decode both the packet number
and the segment number.
2)
There is 4X more data to be read per frame on Lepton 3 compared to Lepton. Therefore, the minimum
SPI clock rate to read a frame of data is 4X higher.
3)
If the sync pulse is enabled (see section 9.2.3), its frequency is 4X higher on Lepton 3 than on Lepton. For
Lepton 3, the sync pulse represents when the next available segment is available whereas for Lepton it
indicates when the next available frame is available.
When telemetry is enabled in Lepton, it results in three extra video lines (63 total packets per frame). When
telemetry is enabled in Lepton 3, it results in 1 additional packet per segment for a total of 2 extra video lines.
5
Thermal Camera Basics
It is noteworthy that the integration period for a thermal detector does not have the same impact on image
formation as it does for a photon detector, such as a typical CMOS array. While a photon detector converts incoming
photons to electrons with near-instantaneous response a microbolometer, such as the Lepton, is always integrating
incident radiation. That is to say, it is always
“active”
regardless of whether or not it is being actively integrated.
The ability to detect high-speed phenomena is more a function of the detector's thermal time constant, which
governs the rate of temperature change. For Lepton, the detector time constant is on the order of 12 msec, which
means that an instantaneous irradiance change will result in a temperature change of the detector as shown in
