Electro-Optical Systems

1. Electro-Optical Systems The almost last lecture of Weapons Class

2. What are we talking about? • Optically guided weapons • Night vision goggles • Thermal Imaging • Laser Guided Munitions

3. Learning Objectives • The student will understand the properties of Infrared radiation. • The student will understand detector features and their effect on performance.

4. Electro-Optical Spectrum • Electro-Optical Band 1011-1016 Hz • Visible ~1015 Hz • Infrared ~1011-1014 Hz • Portion of the EM spectrum that lies between X-rays and microwaves

6. 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

7. 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).

8. 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

9. 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)

10. 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.

11. IR image of a snake eating a mouse

12. Characteristics of Thermal Energy • Attenuation – propagation losses primarily through: • Uneven spreading • Absorption • Scattering • Turbulence • Refractive index fluctuations (Temp, pressure, density)

13. 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

14. Military Uses • Laser guided munitions • Designated from air or ground • Thermal homing missiles • Optical Guidance • Night Vision

15. Night Vision Devices (NVD) • Low light level image intensifiers • Improve night vision • Increase amount of light reaching the eye • Light amplification • NVIS • FLIR

16. 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

17. Image intensifier tube Converts photons to electrons and back again

19. Thermal Imaging

23. LGB

24. TOW

25. TOW

26. Questions?