1. How Things Work Night Vision
Clayton Dordu

2. Outline Different “Generations” Conclusion References Background
Types of Night Vision
Design & Operation Overview
Design
-Photocathode
-Micro Channel Plate
-Phosphors Screen
-Ocular Lens
Different “Generations”
Conclusion
References

3. Night Vision Background
Originally designed for military uses
Kálmán Tihanyi created night vison camera
The German army had the first live action NVDs
The US army had created NVDs used in WWII and the Korean
Four different “generations” of NVDs

4. We will be looking at image enhancement night vision optics
Types of Night Vision
There are two different kinds of night vision:
Image Enhancement
Thermal Imaging
We will be looking at image enhancement night vision optics

5. Design Overview Need to amplify light
Done using a transducer and electron multiplier
Amplify new electric signal and project to screen

6. Operation Overview Light enters into NVD via objective lens
Photons strike photocathode
Electric signal is amplified by a Micro Channel Plate
Image is created on phosphorus screen from electrons striking it
Phosphorus screen is viewed using an ocular lens

7. Operation Overview Image from:

8. Photocathode Transducer used in night vision
Convert the photons from object into electrons
Photons strike an emissive surface that releases an electron
Made possible via the Photoelectric Effect
Similar implementation as solar panels
Surface is vacuumed sealed for better performance

9. Micro Channel Plate (MCP)
Similar to secondary electron multipliers
Electrons enter channels, collide, emit creating avalanche effect
Electric field used for accelerating electrons in channels
Two MCPs in series can create ~108 electrons
Night vision optics have multiple MCPs cascaded together

10. Micro Channel Plate (MCP)
Made of low resistive material
L/d between 40 and 80,
Between 0.4 mm and 3 mm thick
OAR typically 70 to 80%
Channels tilted at angles ranging from 5° to 15 °
Transit time of electrons ~100 ps

11. Micro Channel Plate (MCP
Image from:

12. Phosphors Screen
Cloud of electrons collide with a screen coated in phosphors
Electrons excite the phosphors and a photon is released
This photon is what is seen by the user
Electrons hold same relative pattern as photons had

13. Ocular lens The enhanced image is viewed using an ocular lens
Focuses the image
Magnifies the image
Can be connected to an external screen

14. Night Vision Images Images from:
(left)
(right)

15. Different Generations of Night Vision
Generation I
Generation II
Generation III

16. Generation 0 First NVDs introduced in the 30’s and 40’s
Had an infrared source to illuminate objects
Uses S-1 photocathode AgOCs (Silver-Oxygen-Cesium)

17. Generation I First Introduced in the Vietnam War
No infrared source, relied on ambient light of stars and moon
Didn’t work well on cloudy nights and were unreliable
Uses S-20 photocathode NaKSbCs (sodium-potassium-antimony- cesium)

18. Generation II Had image-intensifier tube ~20,000x light amplification
There are Gen II+ devices as well
Uses S-25 photocathode – same materials as S-20 just thicker layers

19. Generation III Still use micro channel plate
Micro channel plate is coated with an ion barrier
30,000-50,000x light amplification
Use photocathode made of GaAs

20. Comparison of Different Night Vision Generations
Image from:
(left)
(right)

21. Conclusion Photons enter objective lens
Photocathode converts photons to electrons
Electrons are multiplied via multiple micro channel plates
Electron cloud strikes phosphors coated screen
Photons are released from excitation creating enhanced image
Ocular lens focusses and magnifies enhanced image
4 different generations

22. References Slides by Clayton Dordu
Photocathode. hode/index.html (accessed 10 10, 2017).
Micro Channel Plates. (accessed 10 10, 2017).
History of Nigth Vision. (accessed 10 10, 2017).
Tyson, Jeff. Night Vision. gadgets/nightvision3.htm (accessed 10 10, 2017).
Woodford, Chris. How Night Vision Works. 4 12, (accessed 10 10, 2017).
Photocathode. (accessed 10 10, 2017).
Night Vision Device. (accessed , 2017).

23. Questions?