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
