NVG & Night Physiology Flashcards
What are some causes for immediate rejection of the NVG’s
Flickering
Flashing Intermittent Operation
What are some conditions that will NOT cause rejection of goggles
Cosmetic Blemishes (FOBBIC)
- Fixed Pattern Noise- faint hexagonal pattern through the viewing area
- Output Brightness Variation- areas of varying brightness in or across the image area.
- Bright Spots- These are signal induced. A bright spot is a small, bright area that may flicker or remain constant
- Black Spots- These are blemishes in the image intensifier or dirt or debris between the lenses.
- Image Disparity- difference in brightness between the two image intensifier assemblies within the same binocular.
- Chicken wire- irregular pattern of dark thin lines in the field of view either though out the image or in parts of the image
When does the low battery light come on
30 min power left
what is the field of vision
40°
What are the three types of vision? When is each used?
PMS
- Photopic - full daylight
- Mesopic - dawn/dusk
- Scotopic - night
What type of vision is used when wearing NVGs?
Photopic
Dark adaptation is impaired by:
- Cabin pressure altitudes above 5000 feet
- Carbon monoxide (inhaled while smoking)
- Vitamin A deficient diet
- Prolonged exposure to bright sunlight
- Viewing bright light
Describe cones
- active at higher light levels (photopic vision), are capable of color vision and are responsible for high spatial acuity.
- Color sensors, used in high light levels, provide detail.
- Concentrated in center of field of vision, particularly fovea, so look directly at object to use cones. Adapt to light level changes quickly.
Describe rods
- responsible for vision at low light levels (scotopic vision). They do not mediate color vision, and have a low spatial acuity
- Low light and motion receptors
- cannot sense color
- distributed away from center of field of vision, so look away (averted vision) to use rods.
- Slow to react to light level changes. No cones near fovea so “blind spot” (directly in front of eye) there in low light.
Dark adaptation for night flight is achieved by:
- Avoiding bright light for 30 minutes
- Moderate dark adaptation in 20 minutes in dim red light
- If bright light encountered close one sys to preserve night vision
- Keep cockpit lights at a minimum
Describe night scanning techniques
- Scan like daytime in 10 degree sections except:
- Use averted vision
- Use small circular eye movements to avoid fading
- Move eyes slowly to avoid blurring (allow time to focus)
What steps should be taken to cope with illusions created by various lighting conditions?
- Trust your instruments
- Spatial disorientation from illusions can be prevented only by visual reference to reliable fixed points on the ground or to flight instruments.
Describe autokinesis & how is it prevented
- Staring at a single light that results in appearance of the light moving
- You can prevent this from proper scanning
What is empty-field myopia and how can you prevent it?
-the tendency for the eye to focus in at 6-10 feet (2-3 metres) when there are no obvious objects to look at. When we look out at an indistinct background in the sky we can quickly become “near-sighted”.
What is a false horizon and how may it be caused?
- Illusion from lights not aligned with the horizon
- Confusion of linear light pattern for the horizon
- Occurs when horizon is obscured
- Mistake road lights for horizon or city lights
