NVG Flashcards
What are the 5 major structures of the eye?
-cornea
-iris
-pupil
-lens
-retina
What is the purpose of cones in the eye?
-identify colors
-utilized during daylight
-sharp visual acuity due to 1:1 ratio of cone cells to neuron cells
-uses photochemical iodopsin
What is the purpose of rods in the eye?
-operate in low illumination
-identify shades of black, grey and white
-10:1-10,000:1 ratio of rod cells to neuron cells
-utilize photochemical rhodopsin (visual purple)
Describe the day blind spot
-exists because the optic disk contains no photoreceptors cells
-covers an area of 5.5-7.5 degrees
-compensated for by binocular vision
Describe the night blind spot
-occurs when the fovea is inactive in low light
-covers 5-10 degrees
-an object will fade if stared at for longer than 2 seconds
What are the three night vision techniques? (SOS)
-scanning
-Off center viewing
-shapes and silhouettes
What are the three types of vision?
-photopic (day)
-mesopic (dawn/dusk/full moonlight)
-scotopic (dimly lit nights/partial moonlight/starlight)
Monocular cues (GRAM)
- geometric perspective (LAV)
- linear perspective
- apparent foreshortening
-vertical position in the field
-retinal image size (KITO)
-known size of objects
-increasing or decreasing size
-terrestrial association
-overlapping contours
-Aerial perspective (FLP)
-fading of colors and shades
-loss of texture and detail
-position of light source
-Motion Parallax
Describe dark adaptation
-The process by which the eyes become more sensitive to low levels of illumination

-optimal night vision acuity approaches its maximum level in about 30 to 45 minutes
-if the eyes are exposed to bright light after dark adaptation, their sensitivity is temporarily impaired
-illness adversely affects dark adaptation due to higher than normal oxygen consumption rate
Visual Illusions
(FFAACCSSSSVH)
-fascination/fixation
-false horizon
-aerial perspective
-autokinesis
-confusion with ground lights
-cratering
-structural
-size-distance
-size constancy
-shape constancy
-vection
-height-depth perception
How can you identify deteriorating weather conditions at night under NVGs?
(FLASH)
-fog
-loss of moon or stars
-ambient light levels
-shadows
-halo effect
What are the NVG considerations?
(CALMWWADSOS)
-color
-air/ground speed
-lights
-magnification vs. intensify
-weather
-weapons
-aircraft lighting
-depth perception/distance estimation
-spatial disorientation
-obstacle detection
-scanning techniques
Describe the image intensifier of the NVGs.
(6 parts)
-objective lens
-photocathode
-micro channel plate
-phosphor screen
-fiber optic inverter
-eyepiece lens
How does ABC work?
(NVGs)
Automatic Brightness Control
-adjusts MCP voltage to maintain brightness at preset levels by controlling number of electrons that exit the MCP (micro channel plate)
How does BSP work?
Bright Source Protection
-reduces voltage to the photocathode when exposed to bright light sources
What are the NVG characteristics?
(DIALVP)
-definition : a helmet mounted Light intensification device that allows aircrews to conduct operations at terrain flight altitudes during low ambient light levels, to include overcast conditions
-intensification, not magnification
-acuity : enhances visual acuity from unaided 20/200 to approximately 20/25 under optimal conditions
-Limited field of view : 40°
-Voltage low indicator
-Power supply: batteries, aircraft power, or COPs
Describe the counterweight recommendations as pertains to the ANVIS
-recommended initial weight is 12 ounces however, maximum allowable weight is 22 ounces
How can the aviator avoid spatial disorientation when using NVGs?
-avoid making drastic changes in attitude and bank angles, use proper scanning and viewing techniques
What are the operational defects of the ANVIS?
(SEEFFI)
-shading
-edge glow
-emission points
-flashing
-flickering
-intermittent operation
What are the cosmetic blemishes of the ANVIS?
(BBICFO)
-bright spots
-black spots
-image disparity
-chicken wire
-fixed pattern noise (honeycomb)
-output brightness variation
What is OSAP?
Optimal Site Adjustment Point
-The optimal sight picture when the optical axis of the goggles are aligned with your visual line of sight and the goggles eyepieces are at the maximum distance from your eyes that still allows you to see the full field of view
How far/fast does the moon travel in the sky?
Approximately 15 degrees per hour
1 degree every 4 minutes
