In the design of human-machine user interfaces (HMIs or UIs), the Design Eye Position (DEP) is the position from which the user is intended to view the workstation for an optimal view of the visual interface. The Design Eye Position represents the ideal but notional location of the operator's view, and is usually expressed as a monocular point midway between the pupils of the average user. The DEP may also allow for a standardisation of monocular and binocular "Field of View" and may be integrated into the CAD/CAM design system used to define the workstation build.[1]
The DEP is particularly important in those operator workstations, such as the cockpit of a military fast jet, where an accurate reading of information and symbols on displays may be critical. When designing such user interfaces, the DEP is used as the reference point for the location of items (e.g., displays or controls) within the interface.
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The evolution of the human eye - Joshua Harvey
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Transcription
The human eye is an amazing mechanism, able to detect anywhere from a few photons to direct sunlight, or switch focus from the screen in front of you to the distant horizon in a third of a second. In fact, the structures required for such incredible flexibility were once considered so complex that Charles Darwin himself acknowledged that the idea of there having evolved seemed absurd in the highest possible degree. And yet, that is exactly what happened, starting more than 500 million years ago. The story of the human eye begins with a simple light spot, such as the one found in single-celled organisms, like euglena. This is a cluster of light-sensitive proteins linked to the organism's flagellum, activating when it finds light and, therefore, food. A more complex version of this light spot can be found in the flat worm, planaria. Being cupped, rather than flat, enables it to better sense the direction of the incoming light. Among its other uses, this ability allows an organism to seek out shade and hide from predators. Over the millenia, as such light cups grew deeper in some organisms, the opening at the front grew smaller. The result was a pinhole effect, which increased resolution dramatically, reducing distortion by only allowing a thin beam of light into the eye. The nautilus, an ancestor of the octopus, uses this pinhole eye for improved resolution and directional sensing. Although the pinhole eye allows for simple images, the key step towards the eye as we know it is a lens. This is thought to have evolved through transparent cells covering the opening to prevent infection, allowing the inside of the eye to fill with fluid that optimizes light sensitivity and processing. Crystalline proteins forming at the surface created a structure that proved useful in focusing light at a single point on the retina. It is this lens that is the key to the eye's adaptability, changing its curvature to adapt to near and far vision. This structure of the pinhole camera with a lens served as the basis for what would eventually evolve into the human eye. Further refinements would include a colored ring, called the iris, that controls the amount of light entering the eye, a tough white outer layer, known as the sclera, to maintain its structure, and tear glands that secrete a protective film. But equally important was the accompanying evolution of the brain, with its expansion of the visual cortex to process the sharper and more colorful images it was receiving. We now know that far from being an ideal masterpiece of design, our eye bares traces of its step by step evolution. For example, the human retina is inverted, with light-detecting cells facing away from the eye opening. This results in a blind spot, where the optic nerve must pierce the retina to reach the photosensitive layer in the back. The similar looking eyes of cephalopods, which evolved independently, have a front-facing retina, allowing them to see without a blind spot. Other creatures' eyes display different adaptations. Anableps, the so called four-eyed fish, have eyes divided in two sections for looking above and under water, perfect for spotting both predators and prey. Cats, classically nighttime hunters, have evolved with a reflective layer maximizing the amount of light the eye can detect, granting them excellent night vision, as well as their signature glow. These are just a few examples of the huge diversity of eyes in the animal kingdom. So if you could design an eye, would you do it any differently? This question isn't as strange as it might sound. Today, doctors and scientists are looking at different eye structures to help design biomechanical implants for the vision impaired. And in the not so distant future, the machines built with the precision and flexibilty of the human eye may even enable it to surpass its own evolution.
Military Aviation
With collimated displays, such as the cockpit Head Up Display, the projected symbology is aligned very precisely with the outside world to allow for precise delivery of weapons and also for safe landing. Unless located at the Design Eye Position, the pilot cannot see the symbology as it is effectively focussed at infinity. Similarly, Head Down Displays will usually be angled precisely towards the DEP so that all symbols may be equally visible to the pilot without parallax or other display distortion errors.
Pilots who are below or above the 50% percentile point for sitting height, i.e. not of average stature, may need to adjust the seat in order to attain the DEP, even if this means compromising their optimal reach envelope. This is why, for example, rudder pedals may need to be adjustable.
See also
References
- ^ "US Military Standard 1333A, Aircrew Station Geometry For Military Aircraft". Archived from the original on 2007-09-19. Retrieved 2008-03-07.