NVG

1. NVG Night Vision Goggle Operations

2. Presented By: Capt John Withelder 39th Rescue Squadron

3. Turning Night Into Day • “Our Night Vision capability provided the single greatest mismatch of the war” – General Barry McCaffrey, Commander 24th Infantry Division

4. Overview • The visual process • Components of Vision • NVG Theory and Operation • NVG Components • Types of NVGs • Visual Performance • NVG Limitations • Welcome to the NVG Lab

5. The Visual Process • Major structures of the human eye • Cornea, Iris, lens, Retina, Optic Nerve Retina contains two types of photoreceptors, Cones and Rods

6. The Visual Process • Cone cells – Provide the eyes color sensitivity, about 6 to 7 million, and are concentrated on the center of the eye (day vision, require high light, best for resolution and color vision) • Rod cells – Not color sensitive and are the most numerous, about 120 million, and more sensitive than cone cells (night vision, low level light, best for peripheral vision, blind spot at Fovea)

7. Components of Vision • Focal Vision • Limited to the central 2° of vision (Fovea) • Conscious function, slow process • Allows one to clearly identify objects/read displays • Ambient Vision ( peripheral vision) • subconscious function, primary role is to orient an individual in the environment. • Works with focal vision to provide spatial orientation

8. Components of Vision • Dark adaptation • varies from person to person • sensitivity to light increases10,000 fold during the first 30 minutes of dark adaptation • complete adaptation takes 30 to 45 minutes • Extreme exposure to bright light may destroy dark adaptation for hours, even days. • NVG image perceived in shades of green using both rods and cones. ( dark adaptation critical)

9. NVG Development World War II IR (Infra-red) exploitations Early 60’s Army NVG work Generation I tubes Heavy/awkward/Starlight Scope Generation II tubes Early 70’s development Micro channel plate Shorter/lighter/helmet mounted Generation III tubes intensifier tube into the near IR spectrum “Gallium Arsenide” photocathode (Starlight level performance) What we use now

10. Electromagnetic Spectrum

11. NVG Theory • NVGs are electro-optical devices that intensify (or amplify) existing light instead of relying on a light source of their own • They collect reflected ambient light from stars, moon or sky glow made from distant man made sources (i.e. city lights) • Captured ambient light is electronically amplified 2000 to 5000 thousand of times

12. NVG Theory, How They Work • Users do not look through NVG’s, they see an amplified electronic image on a phosphor display • Light enters the NVG through an objective lens and strikes a photo cathode powered by a high energy charge from the power supply. • The energy charge accelerates across a vacuum inside the intensifier and strikes the phosphor screen where the image is focused

13. NVG Theory • NVG’s Invert and focus the image on an image intensifier • Image intensifier convert light into electrons • Electrons strikes phosphor screen creating visible image • Image re-inverted by fiber optics and transmitted to eye-piece • An NVG phosphor screen is purposefully colored green because the human eye can differentiate more shades of green than any other color.

14. NVG Components(Gen 3)

15. Night Vision Goggles

16. Types of NVGs Type I Type II • Direct View • USAFAN/AVS-6 ( ANVIS) • Optical performance better • Type used in HC-130/HH60 Ops. • Indirect View • Use of combiner glass to reflect image on HUD • Less obstruction to pilots field of view

17. NVG Specifications LIMITS: AN/AVS-6AN/AVS-9 VERTICAL MOTION- 19.5mm 16mm FORE AND AFT- 15.8mm 16mm TILT- +/-5 degrees EYE SPAN- 51mm-72mm OBJECTIVE FOCUS- 254mm--> <61cm--> FIELD OF VIEW- 40 degrees MAGNIFICATION UNITY 1X WEIGHT- 500g 790g OPERATING TEMPERATURE- -25F to +125F STORAGE TEMPERATURE- -31F to +159F COST- BETWEEN $7500 and $8500

18. Visual Performance • Vision is limited while using NVGs. • Approximately 40 degree field of view • Light detection ranges increase (missile launch), but recognition of targets and terrain severely limited

19. NVG Limitations • Field of View (FOV)(peripheral vision severely limited) • Current Type I NVGs, 40° FOV • Current Type II NVGs 30° FOV • Normal eye vision FOV 120° x 80° • Resolution capability of 20/25 to 20/40 • Exceeds eyes unaided night vision of 20/200 to 20/400

20. NVG Limitations • Degraded depth perception and distance estimation • NVGs degrade capability of distance estimation and depth perception • Important to remember for landing while using NVG’s • NVGs will not correct for sight deficiencies, but greatly enhance unaided night vision. • NVG use incurs loss of contrast and definition. (New devices continue to correct this problem) • Reduction in FOV requires a constant aggressive visual scan technique for spatial orientation.

21. NVG Limitations • Cockpit light and windscreen interference • Vision degraded by weather conditions such as fog or haze

22. NVG Limitation Corrections • Research and development continues today or image intensifiers in the areas of longer wavelength spectral response, higher sensitivity, larger fields of view and increased resolution

23. NVG Rescue

24. Questions ?

25. Welcome to the NVG Lab • Review NVG Adjustment video • Wear NVGs in the “visual test lane”