BACKGROUND
UAS – Unmanned Aerial Vehicles
(UAV) / drones - come in a variety of configurations, sizes,
and payload capacities with just as many capabilities for
stealth, altitude and speed. Because of this, the range
from the C-UAS platform to the target can vary immensely.
Identification relies on getting highly accurate visual cues
that can be interpreted either by an operator or the internal
Artificial Intelligence (AI) programming in the C-UAS.
Small UAVs are difficult to see even at close ranges.
Larger, more sophisticated UAVs can fly higher with larger
payloads and present a similarly difficult visual detection.
Infrared cameras directed by C-UAS radar systems provide
much needed information to identify the UAV and determine
its threat. The threat of a UAV can be as benign as
surveillance of a secure position or as deadly as an attack
using missiles, bombs, or WMDs (Weapons of Mass Destruction)
including Biological, Chemical, or Radiological.
C-UAS platforms predominately use radio jamming systems
to disable connectivity of the UAV to its base station,
GNSS jamming to disorient the UAV, or spoofing to take
control of the UAV by overpowering the signal from the
original base station. Some C-UAS platforms use kinetic
destruction or net deployment. In a few systems, air
defense systems target UAVs with missiles. In all cases,
accurate targeting requires accurate identification. Ophir
lenses are the key element to long-range accurate identification
both day and night.
Fig. 1. C-UAS system using a combination of electro-optical and
infrared sensors.
SOLUTION
Lens Technical Specifications for C-UAS platforms
The primary goal of any visual (EO or IR) system is to
provide adequate, focused pixels on target. Sandia National
Labs estimates that an operator needs a minimum of
eight (8) pixels on target to determine the threat of a UAV*.
In order to ensure adequate pixels on target, an imaging
system needs to meet specifications of:
- Field of view (FOV) / Focal length: C-UAS systems require
lenses that provide multiple fields of view. This can
be best accomplished with a continuous zoom lens.
Lenses that allow an AI program to optimize the field
of view for the specific situation are key to a faster-
acting system without an operator in the loop.
Proper FOV allows the imaging system to have the
appropriate number of pixels on target. This is measured
using iFOV (instantaneous FOV) to calculate
pixels per meter (PPM) at a specific range.
- Focus: Maintaining focus during field-of-view changes
and the ability to rapidly maintain focus on a quickly
maneuvering object is important to optimized tracking.
- Image Quality: Providing a sharp and clear image
across the entire field-of-view and throughout the full
zoom range is important to tracking UAVs and identifying
a potential threat.
- Interface: Providing the best mechanical interface to
the sensor and the best electronic interface to the
control system is key to integration into a C-UAS
infrared sensor.
Ophir Lens Capabilities for C-UAS applications
Ophir is recognized as a world-class optics design and
manufacturing company. In addition to off-the-shelf designs,
Ophir works with system integrators on customized
lens solutions to meet any application, including C-UAS.
Two Ophir solutions are ideally suited to long-range identification
for C-UAS systems in development today; SupIR®
60 – 1200mm f/4 and SupIR® 80 – 1200mm f/5.5
-
Field of view / Focal length: Ophir's SupIR® 60 –
1200mm f/4 has a narrow FOV that can identify a
small quadcopter at more than 3 kilometers. It is
perfectly suited to MWIR 10μm SXGA sensors. Ophir's
SupIR® 80 – 1200mm f/5.5 can identify the same quadcopter at more than 2.5 kilometers. It is designed
for use with MWIR 15μm VGA sensors. These choices
allow integrators to tailor C-UAS platforms to the
specific customer application. Systems that integrate
these optics provide the operator with enough pixels
on target to allow for quicker reaction time to a threat.
Fig. 2. Ophir's longest FL's long-range continuous zoom lenses for
C-UAS. SupIR 80-1200mm f/5.5 (left), SupIR 60-1200mm f/4 (right)
Fig. 3. SupIR 60-1200mm f/4 MTF performance
- Fig. 3 describes the MTF charts of the 60-1200mm
f/4 lens at both NFOV and WFOV. These charts show
the Sagittal (S) and Tangential (T) components of the
MTF as a function of the spatial frequency at different
field positions across the focal plane for both WFOV
and NFOV. As can be seen, the Sagittal MTF at both
the WFOV and NFOV is close to the diffraction limit
over the whole focal plane, while the Tangential component
is lower, especially at the WFOV.
- Fig. 4 shows the MTF graphs of the SupIR 60-
1200mm f/5.5 lens at both NFOV and WFOV. Similar
to the MTF performance of the 60-1200mm f/4
above, also in this case, the Sagittal MTF at both the
WFOV and NFOV is close to the diffraction limit over
the whole focal plane, while the Tangential component
is lower.
Fig. 4. SupIR 80-1200mm f/5.5 MTF performance
- Focus: All of Ophir's lenses provide focus retention
through the zoom process. This allows systems to
retain acquisition lock on targets of interest and improves
identification of UAV threats. The lenses also
maintain line of sight (LOS) throughout the zoom.
- Image Quality: Ophir is well known for the superior
design of its lenses. This includes off-axis clarity and
providing excellent imagery throughout the zoom
range. Ophir has a world-class design that eliminates
narcissus and vignetting in its zoom lenses. Narcissus
and vignetting interfere with an AI system's ability to
identify threats.
- Interface: Ophir includes OphirSIM™ software with
all of its continuous zoom and multiple FOV lenses to
facilitate integration and communication to the lens.
Ophir offerings for C-UAS Applications
Ophir has many long-range IR continuous zoom lenses
which can be utilized for C-UAS applications. Depending
on the specific scenario – drone size, drone flight altitude,
distance, etc. – the proper lens should be selected. The
following chart presents the identification ranges of our
lenses for specific drone targets. (see page 4)
CONCLUSION
Unmanned Aerial Vehicles (UAV)
and drones become a significant threat in the modern
battlefield. Critical infrastructure is becoming a secondary
battlefront to bad actors who often are set on disrupting
the life of a citizenry. While these targets are not protected
by military forces, they can be protected by C-UAS from
swarm attacks using micro- and mini-drones. Thermal
imaging systems are very effective for C-UAS (Counter
Unmanned Aircraft System) applications. Ophir offers a
large variety of high-quality long distance IR lenses which
can be successfully integrated for these applications.
*Scott Brooks, "Physical Security Center of Excellence (PSCOE) Emerging UAS and Counter-UAS Technologies", presentation for ,Sandia National Lab, 2019.