直升机飞行手册 Helicopter Flying Handbook

时间：2014-11-09 12:30来源：FAA 作者：直升机翻译 点击：次

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.Dynamic acuity
.Recovery from glare
.Function under low illumination
.Information processing
Vision in Flight
The visual sense is especially important in collision avoidance and depth perception. A pilot’s vision sensors are the eyes, even though they are not perfect in the way they function. Due to the structure of the human eye, illusions and blindspots occur. The more pilots understand the eye and how it functions, the easier it is to compensate for these illusions and blindspots. Figureshows the basic anatomy of the
Normal.view Astigmatic.view
Figure 13-2. Example of a view that might be experienced by someone with astigmatism.
The.rods.and.cones.(film).of.
Rods.and
the.retina.are.
cones
the.receptors.which.record.the.image.and.transmit.it.through.the.
Fovea
optic.nerve.to.
(All.Cones)
the.brain.for.interpretation.
Rod.concentration Lens
Iris
Optic.nerve
Retina
PUPIL CORNEA
The.pupil.(aperture).is.the.opening.at.the.center.of.the.irisThe.size.of.the.pupil.is.adjusted.to.control.the.amount.of.light.entering.the.eye. Light.passes.through.the.cornea.(thetransparent.window.on.the.front.of.the.eye).and.then.through.the.lens.to.focus.on.the.retina.
Figure 13-3.The human eye.
human eye and how it is like a camera. A camera is able Visual Acuity to focus on near and far objects by changing the distance Normal visual acuity, or sharpness, is 20/20. A value of between the lens and the film. Objects can be seen clearly 20/80 indicates that an individual reads at 20 feet the letters
at various distances because the shape of the eye’s lens is that an individual with normal acuity (20/20) reads at 80 changed automatically by small muscles. feet away. The human eye functions like a camera. It has
an instantaneous field of view, which is oval and typically measures 120° vertically by 150° horizontally. When both eyes are used for viewing, the overall field of vision measures about 120° vertically by 200° horizontally.
The eye automatically adjusts for the light level experienced. During night flight, the cockpit and instrument lights should be as dim as possible. The eye can then adjust for the outside lighting conditions (ambient lighting) to see outside. The dimmer the inside lighting is, the better you can see outside.
The Eye
Vision is primarily the result of light striking a photosensitive layer, called the retina, at the back of the eye. The retina is composed of light-sensitive cones and rods. The cones in the eye perceive an image best when the light is bright, while the rods work best in low light. The pattern of light that strikes the cones and rods is transmitted as electrical impulses by the optic nerve to the brain where these signals are interpreted as an image.
Cones
Cones are concentrated around the center of the retina. They gradually diminish in number as the distance from the center increases. Cones allow color perception by sensing red, blue, and green light. Directly behind the lens, on the retina, is a small, notched area called the fovea. This area contains only a high concentration of cone receptors. The best vision in daylight is obtained by looking directly at the object. This focuses the image on the fovea, where detail is best seen. The cones, however, do not function well in darkness, which explains why color is not seen as vividly at night as it is during the day.
Rods
Concentrated outside the fovea area, the rods are the dim light and night receptors. The number of rods increases as the distance from the fovea increases. Rods sense images only in black and white. Because the rods are not located directly behind the pupil, they are responsible for most peripheral vision. Images that move are perceived more easily by the rod areas than by the cones in the fovea. If you have ever seen something move out of the corner of your eye, it was most likely detected by rod receptors.

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