By NS Wickramasinghe BSc (Eng)
1/19/2014

1
CONTENTS









INTRODUCTION
HISTORY
GENERATIONS OF NVDs
BASIC WORKING PRINCIPLE
IMAGE INTENSIFIER TUBES
BASIC C...
INTRODUCTION
 HUMAN VISION IS COMPACKED TO VISIBLE RANGE.
 ELECTROMAGNETIC SPECTRUM .
 ENHANCED SPECTRAL RANGE TECHNIQU...
NIGHT VISION TECHNOLOGIES
USED
 IMAGE ENHANCEMENT
 THERMAL IMAGING
IMAGE ENHANCEMENT
 COLLECTS THE TINY AMOUNTS OF LIGHT .
 INCLUDES THE LOWER PORTION OF THE
INFRARED LIGHT SPECTRUM .

 ...
THERMAL IMAGING
 CAPTURES THE UPPER PORTION OF THE
INFRARED LIGHT SPECTRUM.
 IR EMITTED AS HEAT BY OBJECTS INSTEAD

OF S...
INFRA RED

1/19/2014

7
INVENTION OF NIGHT VISION
 “SEEING WITHOUT BEING SEEN” IT IS THE BASIC TACTIC
OF ANY MILITARY FORCE IN THE WORLD.
 NIGHT...
HISTORY / FUTURE OF NVDs
 1930’S - IMAGE CONVERTER TUBE – Basis for NVDs
 LATER NVDs WERE CLASSIFIED AS PER THE

DEVELOP...
SPECTRUM OF NVDs
 NIGHT VISION MONOCULARS/ BINOCULARS
 NIGHT VION WEAPON SIGHTS
 NIGHT VISION GOGGLES

 LONG RANGE NIG...
HOW NIGHT VISION WORKS

1/19/2014

11
ARRANGEMENT OF UNITS IN NVD

1/19/2014

12
1/19/2014

13
HOW NIGHT VISION WORKS


AN OBJECTIVE LENS (CONVEX TYPE) FOCUSING AN IMAGE INTO A
VACUUM TUBE WITH A PHOTOCATHODE AT ONE ...
FOM
 FIGURE OF MERIT OF A NIGHT VISION DEVICE
 IT’S A MEASURE OF THE QUALITY OF THE IIT

FOM= RESOLUTION X SIGNAL TONOIS...
IITs IN NVDs

1/19/2014

16
1/19/2014

17
GENERATION 0
 SO LITTLE, LOW LIGHT AMPLIFICATION
 ADDITIONAL IR –ILLUMINATORS MUST BE USED

FOR OBSERVATION.
(THAT’S WHY...
Cont …

• S-1 photocathode, coated with
silver shifted cesium oxide

• Anode cone, ensures over high
voltage acceleration ...
GENERATION 0 -DISADVANTAGES
 HAD A VERY DISTORTED PICTURE
 SHORT TUBE LIFE DUE TO THE HIGH ELECTRICAL

VOLTAGE.
 HEAVY ...
GENERATION 1
1

 IMAGE INTENSIFIER TUBE USED FOR THE ST TIME (WITH MULTI -

ALKALI PHOTO CATHODE - S-20, coating from pot...
Cont …

Sectional view Gen1, singlestage NVD, low gain

Sectional view Gen1, 3-stage
NVD, generally high gain at low
contr...
GENERATION 2
 MICRO CHANNEL PLATE (MCP) USED IN IIT

INSTEAD OF ANODE CONE.
 PRINCIPLE CHANGED FROM

ACCELERATION  MULT...
STRUCTURE OF IIT

ND
(2

GEN)

 PHOTO CATHODE
 MICRO CHANNEL

 PHOSPER SCREEN

1/19/2014

24
ADVANTAGES OF

ND
2

GEN NVD

 NO IR-ILLUMINATOR NEEDED

 SMALLER IN DIMENTION
 LOW IN WEIGHT

 LIFE SPAN OF IIT - 250...
GENERATION 2+
(SUPPER GEN)
 MORE IMPROVED MCP
 OVER 4 MILLION MICRO CHANNELS

 PHOTO CATHODE-MORE SENSITIVE TO IR

1/19...
GENERATION 3
 NEW COATING FOR PHOTO CATHODE – Ga As

(Gallium Asernic)
 IMPROVED IMAGE RESOLUTION
 6-12 MILLIONs OF MIC...
GENERATION 4
 FILMLESS OR THINFILM TUBES IS USED
 ONLY USED BY US ARMED FORCES
 15000 HRS OF LIFE SPAN

1/19/2014

28
GEN 1

1/19/2014

GEN 2

GEN 3

29
LENSES USED IN NVD
CONVEX LENSES

1/19/2014

30
LENSES IN LONG RANGE NVDs
CONVEX LENS

1/19/2014

31
PRISMS USED IN NVD

1/19/2014

32
BATTERY COVER

1/19/2014

33
DAY LIGHT COVER

1/19/2014

34
DAY LIGHT COVER

1/19/2014

35
EYE GUARD

1/19/2014

36
TYPE OF BATTERY USED IN NVDs
 SIZE

AAA
 SIZE
AA
 SIZE
9V
 LITHIUM 3V

1/19/2014

37
‘O’ RINGS

1/19/2014

38
CARING CASE

1/19/2014

39
MAINTENANCE
 SHOULD NOT OPERATE AT BAD WEATHER

 MUST NOT OPERATE AT DAY TIME
 KEEP NIGHT VISION BINOCULER CLEAN
 CLEA...
Contd.

 MUST NOT APPLY GREAS OR OIL ON LENSES
 THE N/V BINOCULER HAS TO BE IN THE

CARRING CASE WHILE MOVING/TRANSPORT
...
Night vision devices are dependent on every
little light information available
The task of the objective lens to collect a...
PHOTOELECTRIC EFFECT

1/19/2014

43
MICRO CHANNEL PLATE

1/19/2014

44
1/19/2014

45
1/19/2014

46
Upcoming SlideShare
Loading in …5
×

Theory of night vision

1,599 views
1,222 views

Published on

Published in: Education, Technology, Business
0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
1,599
On SlideShare
0
From Embeds
0
Number of Embeds
4
Actions
Shares
0
Downloads
74
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide

Theory of night vision

  1. 1. By NS Wickramasinghe BSc (Eng) 1/19/2014 1
  2. 2. CONTENTS         INTRODUCTION HISTORY GENERATIONS OF NVDs BASIC WORKING PRINCIPLE IMAGE INTENSIFIER TUBES BASIC COMPONENTS MAINTENANCE OF NVDs NIGHT VISION DEVICES USED IN SRI LANKA NAVY
  3. 3. INTRODUCTION  HUMAN VISION IS COMPACKED TO VISIBLE RANGE.  ELECTROMAGNETIC SPECTRUM .  ENHANCED SPECTRAL RANGE TECHNIQUES USES TO VIEW INVISIBLE THINGS.  ENHANCED SPECTRAL RANGE ALLOWS THE VIEWER TO TAKE ADVANTAGE OF NON-VISIBLE SOURCES OF ELECTROMAGNETIC RADIATION
  4. 4. NIGHT VISION TECHNOLOGIES USED  IMAGE ENHANCEMENT  THERMAL IMAGING
  5. 5. IMAGE ENHANCEMENT  COLLECTS THE TINY AMOUNTS OF LIGHT .  INCLUDES THE LOWER PORTION OF THE INFRARED LIGHT SPECTRUM .  AMPLIFYING IT TO THE POINT THAT WE CAN EASILY OBSERVE THE IMAGE .
  6. 6. THERMAL IMAGING  CAPTURES THE UPPER PORTION OF THE INFRARED LIGHT SPECTRUM.  IR EMITTED AS HEAT BY OBJECTS INSTEAD OF SIMPLY REFLECTED AS LIGHT .
  7. 7. INFRA RED 1/19/2014 7
  8. 8. INVENTION OF NIGHT VISION  “SEEING WITHOUT BEING SEEN” IT IS THE BASIC TACTIC OF ANY MILITARY FORCE IN THE WORLD.  NIGHT VISION SERVES FOR THAT PURPOSE.  NIGHT VISION DEVICE INVENTED BASICALLY FOR MILITARY USE.  SCIENTIFIC / CIVILIAN USE SOMETIMES LIMITED OR EVEN FORBIDDEN BY LAW 1/19/2014 8
  9. 9. HISTORY / FUTURE OF NVDs  1930’S - IMAGE CONVERTER TUBE – Basis for NVDs  LATER NVDs WERE CLASSIFIED AS PER THE DEVELOPMENT STAGE OF USED IMAGE INTENSIFIER TUBE (IIT) , AS GENERATION OF NVD  GENERATION 0,1, 2, 2+, 3  GENERATION 4 (ONLY IN US) 1/19/2014 9
  10. 10. SPECTRUM OF NVDs  NIGHT VISION MONOCULARS/ BINOCULARS  NIGHT VION WEAPON SIGHTS  NIGHT VISION GOGGLES  LONG RANGE NIGHT VISION 1/19/2014 10
  11. 11. HOW NIGHT VISION WORKS 1/19/2014 11
  12. 12. ARRANGEMENT OF UNITS IN NVD 1/19/2014 12
  13. 13. 1/19/2014 13
  14. 14. HOW NIGHT VISION WORKS  AN OBJECTIVE LENS (CONVEX TYPE) FOCUSING AN IMAGE INTO A VACUUM TUBE WITH A PHOTOCATHODE AT ONE END  IT RELEASES ELECTRONS BY THE PHOTOELECTRIC EFFECT ON THE INCIDENCE OF INCOMING PHOTONS.  FROM THERE, THE PHOTOELECTRON IS ACCELERATED THROUGH AROUND 5000 VOLTS INTO A TILTED MICROCHANNEL PLATE.  THE HIGH ENERGY ELECTRON RELEASES SOME MICROCHANNEL PLATE ELECTRONS, WHICH FURTHER RELEASE OTHER ELECTRONS, IN A PROCESS CALLED SECONDARY CASCADED EMISSION.  THE MCP IS TILTED TO ENCOURAGE MORE ELECTRON COLLISIONS 1/19/2014 14
  15. 15. FOM  FIGURE OF MERIT OF A NIGHT VISION DEVICE  IT’S A MEASURE OF THE QUALITY OF THE IIT FOM= RESOLUTION X SIGNAL TONOISE RATIO (S/N)  GEN 3 – APPROX 1600 FOM 1/19/2014 15
  16. 16. IITs IN NVDs 1/19/2014 16
  17. 17. 1/19/2014 17
  18. 18. GENERATION 0  SO LITTLE, LOW LIGHT AMPLIFICATION  ADDITIONAL IR –ILLUMINATORS MUST BE USED FOR OBSERVATION. (THAT’S WHY , THEY ARE CALLED ACTIVE NIGHT VISION DEVICES )  IMAGE CONVERTER TUBE WAS USED, NOT THE IMAGE INTENSIFIER TUBE. 1/19/2014 Cont … 18
  19. 19. Cont … • S-1 photocathode, coated with silver shifted cesium oxide • Anode cone, ensures over high voltage acceleration focusing and turning the image up-side-down • P1 phosphor screen, coating out of zinc and cadmium transferred phosphor 1/19/2014 19
  20. 20. GENERATION 0 -DISADVANTAGES  HAD A VERY DISTORTED PICTURE  SHORT TUBE LIFE DUE TO THE HIGH ELECTRICAL VOLTAGE.  HEAVY AND BIG POWER SOURCE  AN AUTOMATIC PROTECTION OF THE PHOTOSENSITIVE TUBE DOES NOT EXIST 1/19/2014 20
  21. 21. GENERATION 1 1  IMAGE INTENSIFIER TUBE USED FOR THE ST TIME (WITH MULTI - ALKALI PHOTO CATHODE - S-20, coating from potassium, sodium, cesium, silver)  LUMINOUS GAIN BETTER THAN GEN. 0 (P-20 phosphor screen)  SERVICE LIFE OF GEN 1 IIT- 1000-2000 HRS  NO AUTOMATIC PROTECTION AGAINST BRIGHT LIGHT  WORKING RANGE 750-800 nm OF IR WAVE LENGTH 1/19/2014 21
  22. 22. Cont … Sectional view Gen1, singlestage NVD, low gain Sectional view Gen1, 3-stage NVD, generally high gain at low contrast 1/19/2014 Cont … 22
  23. 23. GENERATION 2  MICRO CHANNEL PLATE (MCP) USED IN IIT INSTEAD OF ANODE CONE.  PRINCIPLE CHANGED FROM ACCELERATION  MULTIFICATION (electrons)  THE LIFE SPAN INCREASED TO APPROX. 2500 - 5000 H  WORKS WITHIN THE RANGE BETWEEN 780 AND 850 NM WAVELENGTH 1/19/2014 23
  24. 24. STRUCTURE OF IIT ND (2 GEN)  PHOTO CATHODE  MICRO CHANNEL  PHOSPER SCREEN 1/19/2014 24
  25. 25. ADVANTAGES OF ND 2 GEN NVD  NO IR-ILLUMINATOR NEEDED  SMALLER IN DIMENTION  LOW IN WEIGHT  LIFE SPAN OF IIT - 2500- 5000 HRS  AUTOMATIC BRIGHTNESS CONTROL (ABC)  HIGH IMAGE RESOLUTION THAN EARLY GENs. 1/19/2014 25
  26. 26. GENERATION 2+ (SUPPER GEN)  MORE IMPROVED MCP  OVER 4 MILLION MICRO CHANNELS  PHOTO CATHODE-MORE SENSITIVE TO IR 1/19/2014 26
  27. 27. GENERATION 3  NEW COATING FOR PHOTO CATHODE – Ga As (Gallium Asernic)  IMPROVED IMAGE RESOLUTION  6-12 MILLIONs OF MICRO CHANNELS IN MCP  AN THIN ALUMINIUM LAYER ON THE PC (ION BARRIER) IS USED FOR AN ENHANCED SERVICE LIFE SPAN OF IIT- 10000 HRS  IR WAVE LENGTH- 780-920 µm 1/19/2014 27
  28. 28. GENERATION 4  FILMLESS OR THINFILM TUBES IS USED  ONLY USED BY US ARMED FORCES  15000 HRS OF LIFE SPAN 1/19/2014 28
  29. 29. GEN 1 1/19/2014 GEN 2 GEN 3 29
  30. 30. LENSES USED IN NVD CONVEX LENSES 1/19/2014 30
  31. 31. LENSES IN LONG RANGE NVDs CONVEX LENS 1/19/2014 31
  32. 32. PRISMS USED IN NVD 1/19/2014 32
  33. 33. BATTERY COVER 1/19/2014 33
  34. 34. DAY LIGHT COVER 1/19/2014 34
  35. 35. DAY LIGHT COVER 1/19/2014 35
  36. 36. EYE GUARD 1/19/2014 36
  37. 37. TYPE OF BATTERY USED IN NVDs  SIZE AAA  SIZE AA  SIZE 9V  LITHIUM 3V 1/19/2014 37
  38. 38. ‘O’ RINGS 1/19/2014 38
  39. 39. CARING CASE 1/19/2014 39
  40. 40. MAINTENANCE  SHOULD NOT OPERATE AT BAD WEATHER  MUST NOT OPERATE AT DAY TIME  KEEP NIGHT VISION BINOCULER CLEAN  CLEAN LENS WITH 99% ETHIL ALCOHOL  SHOULD NOT DROP DOWN  SHOULD NOT COLLIED WITH ANYTHING 1/19/2014 40
  41. 41. Contd.  MUST NOT APPLY GREAS OR OIL ON LENSES  THE N/V BINOCULER HAS TO BE IN THE CARRING CASE WHILE MOVING/TRANSPORT  REMOVE THE BATTERY BEFORE STORED.  STORED IT AT COOL /DRY PLACE. 1/19/2014 41
  42. 42. Night vision devices are dependent on every little light information available The task of the objective lens to collect as much as possible light and to focus an image on the image intensifier tube's input window Tube can strengthen only the low light passed and collected by the objective lens Appropriate tuning between the optical and electronic part should be take place 1/19/2014 42
  43. 43. PHOTOELECTRIC EFFECT 1/19/2014 43
  44. 44. MICRO CHANNEL PLATE 1/19/2014 44
  45. 45. 1/19/2014 45
  46. 46. 1/19/2014 46

×