Night considerations Flashcards
What chemical develops in your eye to create dark adaptation and how long does it take?
Rhodopsin, and it take 30-45 minutes and within 30 minutes it is 80% developed
What are the three types of vision and what light levels and cell types are they associated with?
Photopic: Day light, Cones
Mesopic: Twilight, both (Most dangerous)
Scotopic: Night Light, Rods
Describe the blind spots.
Retinal blind spot: exists due to a lack of rods and cones where the retina is attached and is compensated by our binocular vision
Night blind spot: caused by a lack of rods in the back of the eye, 5-10*, compensated for by off center viewing
ANVIS acuity levels
optimum light: 20/25
lowest light settings: 20/70
lowest light and low contrast: 20/200
<50% illum: halo effect
<30% illum: scintillation
what are the major components of the ANVIS and what is there function?
5 Pieces
Objective Lens: take in light
Photocathode: transform light into electrodes and flips the image
Microchannel plate: amplifies electron signal
Phosophor screen: converts electrons back into light
Fiberoptic inverter: flips the image again bringing it right-side-up
Effects of weather on ANVIS
A halo effect may begin to appear around lights
as light diminishes static will begin to increase
Can cause pilots to fly into IMC due to greater visual acuity in clouds
Weight bag limitations
Shouldn’t be made of sharp objects
Velcro-ed to the back of the helmet for crash safety
can weight between 12 and 22 ounces
monocular cues
(GRAM)
Geometric perspective (linear perspective, apparent foreshortening, vertical position in the field)
Retinal image size ((known size of objects, increasing or decreasing size of objects, terrestrial association, overlapping contours)
Aerial perspective (fading colors or shades, loss of detail, position of lights)
Motion parralax
ANVIS visual defects
Shading
Edge glow
Emission points
Flashing, flickering, or intermittent operation
ANVIS cosmetic blemishes
Bright spots
Black spots
Chicken wire
Honeycomb
Image disparity
Output brightness variation
Image distortion
Describe the types of active protections the ANVIS provide
Automatic brightness control: The system has an auto-gain function to adjust brightness
Bright source protection: bright sources of light can potentially damage the photocathode, MCP, and the eye. The BSP circuit limits voltage between the photocathode and input side of the MCP. The user will perceive this as the ANVIS temporarily shutting off.
Effects of prolonged exposure to intense sunlight
Intense sunlight exposure of 3 to 5 hours can cause up to 5 hours of slower night adaptation and worse night vision acuity
explain the differences between having the moon at a high angle vs low angle for night flight
A high-angle moon provides greater illumination and reduces shadows that cause distortion
A low-angle moon may be beneficial in areas of low terrain relief
What season may aid in the identification of objects and terrain features at night?
winter, due to the decrease in vegetation and foliage
Describe some of the difficulties that can make over water night flight so dangerous
minimal reference points, poor contrast, and reduced sense of motion parallax may make aviators more susceptible to spatial disorientation
Why is your eye more susceptible to laser damage at night?
The Iris becomes larger to let in more light
