Transcript Electro-Optical Systems

Electro-Optical Systems
The almost last lecture of Weapons
Class
What are we talking about?
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Optically guided weapons
Night vision goggles
Thermal Imaging
Laser Guided Munitions
Learning Objectives
• The student will understand the
properties of Infrared radiation.
• The student will understand detector
features and their effect on
performance.
Electro-Optical Spectrum
• Portion of the EM spectrum that lies
between X-rays and microwaves
• Electro-Optical Band
• Visible
• Infrared
1011-1016 Hz
~1015 Hz
~1011-1014 Hz
Sources of EO Radiation
• Turbojet exhaust, a tank engine, or a
person
• Lasers may serve as illuminator for an
IR weapon’s guidance
• Man-made artificial illumination (lights,
flares, etc)
• Natural sources
Sources (Radiators)
• Selective Emitters
– Narrow wavelength band – line spectra
– Excitation of individual atoms or molecules
• Thermal
– Continuous spectrum of wavelengths with
some max radiated energy at some
particular λ
– Radiates in proportion to the absolute
temperature (Kelvin).
Lasers
• Laser is light – a form of EM radiation
• Light Amplification by Stimulated
Emission of Radiation
• Can emit in the ultraviolet, visible, and
infrared portions of the spectrum
Lasers – Military Applications
• Targeting tool
– Absorbed by target – thermal radiator
– Reflected by target – selective radiator
• Modulated
– Different lasers of the same frequency to be
deconflicted and limits enemy interference
• Weapon Systems: Hellfire, Maverick, Rockeye
• Stand alone: Laser Range finders, Beam
riders, and laser target designators (LTD)
Infrared
• Can not be detected with the human
eye
• Passive system that collects thermal
radiation emitted from the target.
• Used in military and law enforcement
applications.
IR image of a snake eating a mouse
Characteristics of Thermal Energy
• Attenuation – propagation losses
primarily through:
– Uneven spreading
– Absorption
– Scattering
– Turbulence
• Refractive index fluctuations (Temp, pressure,
density)
Detectors
• Photon
– Convert absorbed photon energy into
released electrons
• Themal
– Absorb energy over a broad band of
wavelengths
– Causes tempurature of material to increase
• At least one inherent electrical property that
changes with temperature
Military Uses
• Laser guided munitions
– Designated from air or ground
• Thermal homing missiles
• Optical Guidance
• Night Vision
Night Vision Devices (NVD)
• Low light level image intensifiers
• Improve night vision
– Increase amount of light reaching the eye
– Light amplification
• NVIS
• FLIR
Night Vision Scopes
• “Amplify” existing light
• Available light (photons) is collected
and focused on the image intensifier
• Conversion of photon to electron
• CAN NOT see in complete dark
– IR illuminator
Image intensifier tube
Converts photons to electrons and back again
Thermal Imaging
LGB
TOW
TOW
Questions?