NVGNVGNight Vision Goggle OperationsNight Vision Goggle Operations

Presented By:Presented By:

Capt John WithelderCapt John Withelder

39th Rescue Squadron39th Rescue Squadron

Turning Night Into DayTurning Night Into Day

• ““Our Night Vision capability provided the single Our Night Vision capability provided the single greatest mismatch of the war” – General Barry greatest mismatch of the war” – General Barry McCaffrey, Commander 24McCaffrey, Commander 24thth Infantry Division Infantry Division

OverviewOverview• The visual processThe visual process

• Components of VisionComponents of Vision

• NVG Theory and OperationNVG Theory and Operation

• NVG ComponentsNVG Components

• Types of NVGsTypes of NVGs

• Visual PerformanceVisual Performance

• NVG LimitationsNVG Limitations

• Welcome to the NVG LabWelcome to the NVG Lab

The Visual ProcessThe Visual Process

• Major structures of the human eyeMajor structures of the human eye– Cornea, Iris, lens, Retina, Optic NerveCornea, Iris, lens, Retina, Optic Nerve

Retina contains two types of photoreceptors, Retina contains two types of photoreceptors, Cones and RodsCones and Rods

The Visual ProcessThe Visual Process

• Cone cells – Provide the eyes color sensitivity, Cone cells – Provide the eyes color sensitivity, about 6 to 7 million, and are concentrated on the about 6 to 7 million, and are concentrated on the center of the eye (day vision, require high light, center of the eye (day vision, require high light, best for resolution and color vision)best for resolution and color vision)

• Rod cells – Not color sensitive and are the most Rod cells – Not color sensitive and are the most numerous, about 120 million, and more sensitive numerous, about 120 million, and more sensitive than cone cells (night vision, low level light, best than cone cells (night vision, low level light, best for peripheral vision, blind spot at Fovea)for peripheral vision, blind spot at Fovea)

Components of Vision Components of Vision

• Focal VisionFocal Vision– Limited to the central 2° of vision (Fovea)Limited to the central 2° of vision (Fovea)

– Conscious function, slow processConscious function, slow process

– Allows one to clearly identify objects/read displaysAllows one to clearly identify objects/read displays

• Ambient Vision Ambient Vision ( peripheral vision)( peripheral vision)

– subconscious function, primary role is to orient an subconscious function, primary role is to orient an individual in the environment.individual in the environment.

– Works with focal vision to provide spatial orientationWorks with focal vision to provide spatial orientation

Components of VisionComponents of Vision

• Dark adaptationDark adaptation– varies from person to personvaries from person to person– sensitivity to light increases10,000 fold during sensitivity to light increases10,000 fold during

the first 30 minutes of dark adaptationthe first 30 minutes of dark adaptation– complete adaptation takes 30 to 45 minutescomplete adaptation takes 30 to 45 minutes– Extreme exposure to bright light may destroy Extreme exposure to bright light may destroy

dark adaptation for hours, even days.dark adaptation for hours, even days.– NVG image perceived in shades of green using NVG image perceived in shades of green using

both rods and cones. both rods and cones. ( dark adaptation critical)( dark adaptation critical)

NVG DevelopmentNVG 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

Electromagnetic Electromagnetic SpectrumSpectrum

NVG TheoryNVG Theory• NVGs are electro-optical devices that intensify (or NVGs are electro-optical devices that intensify (or

amplify) existing light instead of relying on a light amplify) existing light instead of relying on a light source of their ownsource of their own

• They collect reflected ambient light from stars, They collect reflected ambient light from stars, moon or sky glow made from distant man made moon or sky glow made from distant man made sources (i.e. city lights)sources (i.e. city lights)

• Captured ambient light is electronically amplified Captured ambient light is electronically amplified 2000 to 5000 thousand of times2000 to 5000 thousand of times

NVG Theory, How They NVG Theory, How They WorkWork

• Users do not look through NVG’s, they see an Users do not look through NVG’s, they see an amplified electronic image on a phosphor displayamplified electronic image on a phosphor display

• Light enters the NVG through an objective lens Light enters the NVG through an objective lens and strikes a photo cathode powered by a high and strikes a photo cathode powered by a high energy charge from the power supply.energy charge from the power supply.

• The energy charge accelerates across a vacuum The energy charge accelerates across a vacuum inside the intensifier and strikes the phosphor inside the intensifier and strikes the phosphor screen where the image is focusedscreen where the image is focused

NVG TheoryNVG Theory

• NVG’s Invert and focus the image on an image NVG’s Invert and focus the image on an image intensifierintensifier

• Image intensifier convert light into electronsImage intensifier convert light into electrons• Electrons strikes phosphor screen creating visible imageElectrons strikes phosphor screen creating visible image• Image re-inverted by fiber optics and transmitted to Image re-inverted by fiber optics and transmitted to

eye-pieceeye-piece• An NVG phosphor screen is purposefully colored green An NVG phosphor screen is purposefully colored green

because the human eye can differentiate more shades of because the human eye can differentiate more shades of green than any other color.green than any other color.

NVG ComponentsNVG Components(Gen 3)(Gen 3)

Night Vision GogglesNight Vision Goggles

Types of NVGsTypes of NVGs

• Direct ViewDirect View

• USAFUSAF AN/AVS-6 AN/AVS-6 ( ANVIS)( ANVIS)

• Optical performance betterOptical performance better

• Type used in HC-130/HH60 Type used in HC-130/HH60 Ops.Ops.

Type IType I Type IIType II

• Indirect ViewIndirect View

• Use of combiner glass to Use of combiner glass to reflect image on HUDreflect image on HUD

• Less obstruction to pilots Less obstruction to pilots field of viewfield of view

NVG SpecificationsNVG Specifications

LIMITS:

AN/AVS-6 AN/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

Visual PerformanceVisual Performance

• Vision is limited while using NVGs.Vision is limited while using NVGs.– Approximately 40 degree field of view Approximately 40 degree field of view

• Light detection ranges increase (missile launch), but Light detection ranges increase (missile launch), but recognition of targets and terrain severely limitedrecognition of targets and terrain severely limited

NVG LimitationsNVG Limitations

• Field of View (FOV)Field of View (FOV)(peripheral vision severely limited)(peripheral vision severely limited)

– Current Type I NVGs, 40° FOVCurrent Type I NVGs, 40° FOV

– Current Type II NVGs 30° FOVCurrent Type II NVGs 30° FOV

– Normal eye vision FOV 120° x 80°Normal eye vision FOV 120° x 80°

• Resolution capability of 20/25 to 20/40Resolution capability of 20/25 to 20/40– Exceeds eyes unaided night vision of 20/200 to 20/400Exceeds eyes unaided night vision of 20/200 to 20/400

NVG LimitationsNVG Limitations

• Degraded depth perception and distance Degraded depth perception and distance estimationestimation– NVGs degrade capability of distance estimation and NVGs degrade capability of distance estimation and

depth perceptiondepth perception– Important to remember for landing while using NVG’sImportant to remember for landing while using NVG’s

• NVGs will not correct for sight deficiencies, but NVGs will not correct for sight deficiencies, but greatly enhance unaided night vision.greatly enhance unaided night vision.

• NVG use incurs loss of contrast and definition. NVG use incurs loss of contrast and definition. (New devices continue to correct this problem)(New devices continue to correct this problem)

• Reduction in FOV requires a constant aggressive Reduction in FOV requires a constant aggressive visual scan technique for spatial orientation.visual scan technique for spatial orientation.

NVG LimitationsNVG Limitations

• Cockpit light and windscreen interferenceCockpit light and windscreen interference

• Vision degraded by weather conditions such Vision degraded by weather conditions such as fog or hazeas fog or haze

NVG Limitation NVG Limitation CorrectionsCorrections

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

NVG RescueNVG Rescue

Questions ?Questions ?

Welcome to the NVG LabWelcome to the NVG Lab

• Review NVG Adjustment videoReview NVG Adjustment video

• Wear NVGs in the “visual test lane”Wear NVGs in the “visual test lane”