composite video image from the
headset’s thermal imaging camera,
overlay the desired text and graphic
information onto the image, and send
the newly-created video signal to the
headset’s microdisplay. I incorporated a
simple MEMS-based accelerometer to
detect movement of the wearer or lack
thereof, a digital pressure transmitter to
convey the pressure (and remaining
percentage) of the tank of compressed
breathing air, and an RFID (Radio
Frequency Identification) module used
to read the unique identifiers of low-cost
RFID tags and to serve as a robust
Firefighter Identification System.
Infrared Thermal
Imaging Camera
and Heads-Up
Joe modeling the PyroPack: headset (left) and backback (right). (Photos by Boj Florido.)
Microdisplay
onto the thermal imaging camera image — is where the
PyroPack’s sensor information is displayed:
The headset contains an L-3 Communications
Thermal-Eye 3600AS OEM infrared thermal imaging
camera core ( www.thermal-eye.com/products/
3600as.htm) and eMagin SVGA OLED-XL Microdisplay
with WFO5 Prism Optic and Module ( www.emagin
com/products/OLEDMD/OLED-XL.php). The headset
attaches to the side of a standard firefighter SCBA (
Self-Contained Breathing Apparatus) mask and is adjustable by
sliding the entire unit in front of the wearer’s field-of-view
(over his left eye). It can also slide completely out of the
way, allowing for an unobstructed view of the area when
desired. Because the thermal imaging camera is forward
facing and in direct line-of-sight with the wearer’s eye, the
image provided by the camera is a thermal view of the
exact scene the wearer would normally see with his eye.
Retail price of both the thermal imaging camera and
microdisplay are in the tens of thousands of dollars. As our
budget could not support such expenses, L-3 and eMagin
graciously provided the units to us for use on the episode
at no cost. Video overlay is achieved with a Decade
Engineering BOB-4-H Video On-Screen Display module
( www.decadenet.com/bob4/bob4.html). Controlling the
text and graphics to overlay on the composite video
image sent by the thermal imaging camera was achieved
simply by sending a small number of commands via serial
interface to the BOB-4-H.
1. Information pertaining to the Firefighter
Identification System (not shown in this image).
2. Motion detection status (triggers an alert when
no motion of the wearer is detected for a pre-set amount
of time).
3. Remaining percentage of compressed breathing air
available in the wearer’s on-board tank (based on a full
tank pressure of 3,000 PSI).
Motion Detection
A Memsic 2125-GL two-axis accelerometer
( www.memsic.com or www.parallax.com; search for
product code ‘28017’) serves as a motion detection
mechanism. When no motion of the wearer is detected
for 30 seconds, a “MAYDAY” text is overlaid on the heads-up microdisplay image to alert and/or remind the wearer
that he needs to keep moving. Support exists in the
electronics to enable a transistor which will switch on or
off a relay. The relay can be connected to many types of
alerting devices (such as wireless transmitters) to wirelessly
broadcast to all personnel within range that the wearer is
in distress and not moving, or to visible or audible
indicators (such as flashing lights or high-decibel sirens).
The microdisplay’s primary image is that of the
infrared thermal imaging camera. The temperature scale
on the right side of the screen is a feature of the camera
and denotes the temperature in degrees Fahrenheit of
whatever object is positioned in the center of the thermal
imaging camera’s field-of-view. The lower portion of the
display — defined by a white box and black text overlaid
Status of Remaining
Breathing Air
Currently existing pressure gauges are bulky units that
are mounted on the outside of the firefighter (typically to
the frame of their pack), so the gauges are commonly in
the way, bouncing around during active movement, and
June 2010 41
