EXAM ( NVG ) Flashcards
eye anatomy
What is the Cornea ?
Transparent outer part of the eye
(protects the eye)
Eye anatomy
What is the iris ?
Colored membrane around the pupil (allows light into the eye)
Eye anatomy
What is the pupil ?
Opening in the eye
(adjust to available light)
Eye anatomy
What is the purpose of the lens?
It focuses light on the retina (rods/cons) - elastic when young, hardens when older
Eye anatomy
What is it called when the lens hardens in the 40s ?
Presbyopia
Eye anatomy
What is the retina ?
The light sensitive portion of the eye - contains rods and cones
CoL
What component of the eye adjust pupil size to allow light into the eye ?
Iris
What are the 3 types of visions ?
Scotopic
Mesopic
Photopic
At what point does the cones go “offline” ?
When the scotopic vision is active
When are the cones functioning best ?
During the day under “photopic” vision
When are the rods most effective ?
During the night - when adapted - Scotopic vision
Which (Rods / Cones) don’t see color and has a low acuity?
Rods
Does rods work when using photopic vision ?
Yes - but less effective
Does cons work when using scotopic vision ?
No
What is the “Fovea centralis” ?
Night blind spot
A position of the retina with only cons
Where is the night blind spot placed ?
15 degrees of center
Central vision
absence of rod cells in fovea
What is the “optic disk”
Day blind spot
Where optic nerve enters the eye
15 degrees from Fovea
What characterise “Photopic vision”
Cones
Central vision
Best acuity
Best color perception
Daylight / Artificial light
What characterise “Mesopic vision”
Both rods and cones
Central and off-center vision
Decreased acuity
Decreased color perception
Dawn, dusk, NVG
What characterise “Scotopic vision”
Rods only
Off-center vision
Lowest acuity
No color perception
partial moon and starlight
Rhodopsin requires ____ to see at night
buildup
How long does it take for Rhodopsin to build up ?
30-45 min
What type of vision do we use when using NVGs
Mesopic
Effects of bright light is dependent on ____
Duration and intensity
How long does it take to recover from “flash blindless” ?
5-45 minutes depending on duration and intensity
How should the cockpit illumination be ?
Lowest easily readable level
How much of the vision does the
night blind spot
& day blind spot
encompasses
Day: 5.5 - 7.5 degrees
Night: 5 - 10 degrees
Name the scanning techniques
- Stop-turn-stop-turn
- Ten degree circular overlap
- Off-center viewing
CoL
Why is the circular overlap in a scan pattern 10 degrees ?
To ensure coverage og an area greater than the night blind spot
What are the types of visual cues that aid depth perception and distance estimation ?
explain them
Monocular : “GRAM”
Derived from experience - subject to interpretation. Better at larger distances. Assist in Identifying hazards
When using NVGs - acuity decreases - cues will be less and result in poorer depth perseption
Binocular : Cues only valuable when object is close - 10m or less - and each eye view object slightly different. Aids depth perception
Name the monocular cues
Geometric perspective
Objects have different shapes dependent on how viewed
Retinal image size
An image focused on the retina is perceived by the brain to be of a given size
Aerial perspective
An objects clarity and shadow help estimate distance
Motion parallax
The apparent relative motion of stationary objects as viewed by a moving observer
How does monocular cues improve ?
With experience
CoL
What information does motion parallax provide aviators
Aircraft speed and direction of movement
Describe the operational sequence of the NVGs
- Objective lens (Flips image)
- Photocathode (Turns photons to electrons)
- Microchannel plate (Multiply electrons)
- Phosphor screen (Creates image from electrons - glows)
- Fiber optic inverter (flips image to normal)
- Eye piece lens
What is installed to protect:
1. The pilot
2. The NVGs
- Automatic brightness control (ABC)
- Bright-source protection (BSP)
How does the ABC work ?
When light is too bright - the electrically charged micro channel plate increases charge - less electrons created = dims picture
How does the BSP work ?
To protect the micro channel plate the electrically charged photocathode is actived reducing the amount of electrons reaching the next plate
Which lense assembly contain the minus blue coating which filters out lgiht from the aircraft instrument panel ?
Objective lens
What is the NVGs (ANVIS) field of view ?
40 degrees
What is the NVGs acuity - best & worst case ?
Best: 20/25
Worst: 20/70
When illumination decreases - what (effects of low acuity) increases ?
Halo & Scintillation
What is “halo” a result of ?
Electron scatter between photocathode and microchannel plate
Halos are ____ present and ____ does not change
always, size
Where on the light spectrum does the NVG pick up inputs?
Photopic and near IR
CoL
Which component of the image intensifier is responsible for creating the monochromatic viewing image ?
Phosphor screen
True / False
Because the ANVIS eyepiece can correct for individual eye acuity, operators are not required to wear noramlly required eyeglasses
False
What are the ANVIS visual deficiencies ?
Operational defects
immediate cause for rejecting the ANVIS
Cosmetic blemishes
Pilot discretion to fly with these
Name the operational defects
Shading
Emission points
Edge glow
Flashing / flickering and intermittent operation
What is number 1 called
Fore and aft adjustment knob
What is number 2 called ?
Eye span adjustment knobs
What is the pink part called ?
Pivot and adjustment shelf PAS
What is the pink part called ?
Objective lens assembly
What is the pink part called?
Eyepiece lens assembly
What is number 6 called
Tilt lever
Why is it important to use the lens caps ?
Because sunlight can damage the tubes even with the caps on
What is this called ?
HUD clamp
What is this called ?
Vertical adjustment knob
What is this called ?
Lock release button
What should you use when flipping the binoculars up and down?
The lock-release button
Always attach or remove the ANVIS from a ____ position
middle
Low profile power pack
Which side is the primary (batteries) ?
the right side
What are the two types of batteries authorized for the ANVIS ?
Alkaline and 1.5v Lithium
Which form is related to the NVGs (ANVIS)
Discrepancies, dates ect.
DA FORM 2408-30
Low BAT indicator
If the low battery indicator starts flashing when ANVIS battery life has approximately ____ min remaining
30 minutes
Clean dirty contact points of the NVGs using ?
Pencil eraser
What is the only thing approved for cleaning the lenses ?
Lens papers
What is OSAP ?
Optimal sight adjustment point
When does the optimal sight picture occur ?
- When optical axes are aligned with your visual line-of-sight
- The googles eyepieces are the maximum distance from your eyes while still providing the entire image
OSAP
What is the final adjustment ?
Use the fore and aft adjustment to move the googles slightly closer to the eye (about 1/2 turn)
How do you focus the “objective focus ring” ?
- Remain both eyes open
- Cover one objective
- Focus on target (atleast 50m away)
- Turn objective lens to target in focus - past focus - back in focus
What is number 3/4 called ?
Objective focus rings
What is number 7/8 called ?
Eyepiece focus ring
How do you focus the “eyepiece lens” ?
Slowly turn the eyepiece lens focus ring counterclockwise until objective blur - pause for eye to relax - turn eyepiece clockwise until image is in focus
CoL
Use both hands to remove the ANVIS from the mount
True or false
True
What are the 3 sources of natural light ?
Sun, moon and stars
Why is distance estimation and depth perception hard at night?
Because the monocular cues are less useful and reliable
What are the indications of reduced ambient light levels ?
Halo
Scintillation
loss of celestial and ground lights
loss of scene detail
What is sky glow?
Effect that the sun has on NVGs for approximately one hour before and after sunrise/sunset
What power supply function can be activated when experiencing battlefield light sources ?
BSP
Which cues are primarily used for distance estimation and depth perception ?
Monocular cues (learned cues)
Effective use of monocular cues requires ____ and ____in various terrain types and flight enviroments
Training and experience
What is the greatest source of natural illumination at night ?
Moon ( moves 15 degrees per hour )
What does the googles improve ?
for the aviator
Situational awareness
What is “decreased NVG gain” ?
When BSP comes on and decreases the number of electrons
Does ABC work constantly ?
Yes
Is BSP always working ?
No - only when it has to to protect the goggles
True/False : it’s good to fly in shadows at night
False!
We don’t fly in shadows.
Which type of radiation is still present in the sky after sunset ?
IR light
Sky glow ____ NVG gain ?
decreases
Avoid ____ areas (referring to lighting)
brightly lit
What is the most common form of tactical airfield lighting ?
Inverted Y
If you are using terrain features for navigation, they must be unic in ____
shape
Why is backlighting a problem ?
Bright lit areas/cultural lights can washout a/c and “hide” them from the observer
What is this called ?
Spring loaded ball bearings
What does the minus blue filter do ?
Makes the ANVIS blind to cockpit lighting
filters out blue/green cockpit lighting
The ______ flexes so the light entering the eye is properly focused
on the retinal wall
Lens
________ cells are used primarily for day or high intensity light
vision (viewing periods or conditions). ________ cells are used for
night or low-intensity light vision (viewing periods or conditions).
Cone, Rod
The optic disk is where the optic nerve enters the retina. Because
the optic disk contains neither rods nor cones, nothing can be seen
by that part of the retina. This is called the day blind spot. How do
we compensate for the day blind spot?
By viewing with Binocular Vision
Of the three types of vision, which type uses both rods and cones
and is characterized by decreasing acuity and decreased color
perception?
Mesopic
How long does it take for the average person to attain the greatest
sensitivity or adaptation to a dark environment?
30 - 45 min
Dark adaptation can be lost due to exposure to bright light. How
long does it take to recover dark adaptation?
It depends on the duration and intensity of the exposure.
The night blind spot occurs due to the total absence of rod cells in
the fovea and the lack of rod cell stimulation within the parafoveal
regions. How do we compensate for the night blind spot?
By using proper scanning techniques and off-center viewing
Which visual illusion is described as missing or ignoring orientation
cues in order to focus their attention on an object or goal?
Fascination or fixation.
Which visual illusion is described as a falsely perceived self-motion
in relation to another object’s motion?
Vection
Which monocular cue provides aircraft speed and direction of
movement?
Motion Parallax
True or False? While adjusting the eyepiece focus ring, during the
focus procedures, one eye should remain closed.
False
Which of the following statements is TRUE about battery usage
with ANVIS?
3 1.5v Lithium batteries and AA Alkaline batteries may not be
mixed within the same cartridge.
How is the Low Profile Power Pack (LPPP) correctly mounted to
the helmet?
With the On-Off-On switch oriented to the top of the helmet.
True or False? The eyepiece diopter adjustment can compensate
for vision deficiencies. It is therefore not necessary to wear
corrective lenses in flight.
False
What is the MAXIMUM weight allowable for the counterweight
(weight bag)?
22 ounces
What is the function of Automatic Brightness Control (ABC)?
The ABC automatically adjusts voltage to the MCP to keep the
image intensifier’s brightness within a set limit for the operator.
What frequencies of light are visible to the ANVIS?
The ANVIS is sensitive to the visible spectrum and near-infrared
range.
What is the function of the minus blue filter inside the objective
lens?
It makes the ANVIS “blind” to the instrument lighting so the glare
does not interfere with viewing outside the aircraft.
When the blinking LED light on the helmet activates, how much
longer will the NVG continue to operate under worst-case
conditions?
Approximately 30 minutes.
Which of the following statements is TRUE about mounting and
dismounting the ANVIS?
2 Grasp the ANVIS using both hands at the PAS and mount or
dismount the ANVIS as a unit at the middle position.
Best possible visual acuity for the ANVIS is achieved under
optimum conditions - 100% illumination, clear skies, with a highcontrast
background. What acuity can be achieved under optimum
conditions?
20/25
Which battery compartment will house the primary batteries?
The compartment on the wearer’s right.
From the following list, select the operational defects of the ANVIS:
2 Shading, Emission Points, Edge Glow and Flashing, Flickering,
or Intermittent Operation. (SEEF)
True or False? Cosmetic blemishes are an immediate cause for
rejecting the ANVIS.
False
Which of the following statements is TRUE regarding the Optimal
Sight Adjustment Point (OSAP) procedure?
2 Disregard focusing at this time; it is actually better to have the
objective lenses out of focus for this procedure.
Which of the following statements is FALSE about flying in a dusty
or sandy environment?
1 After operation, disassemble the ANVIS and thoroughly clean all
components.
Which of the following statements is FALSE about flying in a desert
environment?
2 Terrain flight in desert areas is easier because of the good
contrast.
From the statements below, select the statement which BEST
describes the characteristics of the moon:
3 At night the moon is the highest percentage of natural
illumination, and changes angles at the rate of 15 degrees per hour.
Which of the following is NOT an indication of restrictions to
visibility while operating NVGs?
3 Increased visual acuity.
What is the procedure for cleaning the contacts on the helmet
mount?
Clean the contacts with a regular pencil eraser.
Worst-case conditions can reduce ANVIS visual acuity to
approximately 20/70. Which of the following is NOT a contributor to
‘worst-case conditions’?
A high-contrast background.
From the following statements, select the TRUE statement about
terrain relief:
1 Terrain features that are unique in shape are excellent
checkpoints.
From the following list, select the COMMAND consideration for
NVG/night mission planning:
3 Crew Endurance.
All of the following are NVG/night mission briefing considerations
EXCEPT:
2 Only the pilot in command of each aircraft is required to attend
the formal briefing.
From the following list, which is NOT an NVG/night checkpoint
planning consideration?
1 Select ACPs/checkpoints near brightly lighted areas such as
built-up areas and towns.
Which of the following statements about NVG Tactical lighting is
TRUE?
2 The most common technique of lighting an area for aviation use
is the inverted Y.
Which of the following statements about cockpit lighting is FALSE?
2 Supplemental lighting must be red or amber in color.
What is the pink part called ?
Dual contact
What is the pink part called ?
Spring loaded ball bearings
Which side of the ANVIS is the pink side / green side ?
Pink side : Eyepiece (eyepiece lense assembly)
Green side : Objective (Objective lense assembly)
Name the part of the ANVIS/NVGs that the green/pink arrows are pointing to
Pink: Objective lens caps
Green: Eyepiece lens caps
Which type of lighting washes out the other under ANVIS ? LED / incandescent
Incandescent lights washes out the LED light under ANVIS
More aircrafts (UH60/C130) uses LED light for position lights to reduce cost. Under ANVIS this means you might miss them if enough incandescent light is present to wash out the LED lighting. This can be compromised for by verifying scene with unaided eye.
Does supplemental lighting have to pass the army dagredation test?
Yes
White light recommmended - not mandatory
How far should the distance be between lightsources when only two are available for LZ/PZ
15 feet
What is the minimum weight for the NVG weight bag ?
0 oz
What does the eyepiece focus rings adjust for ?
Individual eye acuity (difference in the two eyes)
