Mask subs (also half mask , diving mask or scuba mask ) is a dive utility item that allows underwater divers , including, scuba divers, free divers, and snorkelers to see clearly underwater. Surface-supplied dives typically use full face masks or dive helmets, but in some systems, half masks may be used. When the human eye is in direct contact with water as opposed to air, its normal environment, the light entering the eye is refracted by different angles and the eye can not focus light. By providing an air space in front of the eye, light enters normally and the eye can focus properly.
When the diver experiences increased ambient pressure and it is necessary to equalize the pressure inside the mask with ambient pressure to avoid the barotrauma known as the squeeze mask, This is done by blowing enough air out through the nose into the mask to reduce the pressure. difference. This requires that the nose be inserted in the air chamber of the diving mask. Equations during automatic climbing because excess air easily leaks past the seal from the inside.
Corrective lenses can be mounted to allow normal vision for people with focus defects, or contact lenses can be worn inside the mask.
A wide variety of viewport shapes and internal volumes are available, and each design will generally match some face shapes better than others. A good comfortable fit is important for the correct mask function.
Video Diving mask
Function
Light rays bend as they travel from one medium to another; the amount of bending is determined by the refractive index of the two media. If one medium has a particular curved shape, it acts as a lens. The cornea, humor, and eye crystal lenses together form the lens that focuses the image on the retina. Our eyes are adjusted to be seen in the air. Water, however, has approximately the same refractive index as the cornea (both about 1.33), so effective immersion removes the corneal focusing properties. When our eyes are in water, instead of focusing images on the retina, they now focus them far behind the retina, resulting in a very blurry image of hypermetropia.
By wearing flat diving masks, humans can see clearly under the water. The flat scuba mask window separates the eyes from the surrounding water with a layer of air. The incoming light from the water to the flat parallel window changes its direction minimally within the window material itself. But when these rays come out the window into the air space between the flat window and the eye, the refraction is quite visible. The outline view refracts (bent) in a similar way to seeing the fish stored in the aquarium. Linear polarization filters lower visibility under water by limiting ambient light and dimming artificial light sources.
The refraction of light entering the mask makes the object appear approximately 34% larger and 25% closer when under water. Also distorted bearings and lateral chromatic aberrations are seen. When the diver descends in clean water, the water acts as a color filter that removes the red end of the visible sunlight spectrum entering the water leaving only the blue end of the spectrum. Depending on the depth and clarity of the water, eventually all sunlight is blocked and the diver must rely on an artificial light source to see underwater.
Maps Diving mask
Construction
There are two basic categories of diving masks: Mask half covering the eyes and nose, and full face mask covering the eyes, nose and mouth, and therefore include part of the breathing apparatus. Half the mask is described here.
Diving masks may have single, durable, tempered faceplate glass, or two lenses in sight. This may be supported by relatively rigid plastic or metal frames, or they can be permanently bonded to the edge of the skirt, in a construction known as "without borders." In the case of a freediving mask, which needs to have a low internal volume to minimize the amount of breath needed to equalize the pressure changes that occur with depth, the lens can be made of polycarbonate plastic. There is usually a "skirt" of synthetic rubber or silicone elastomers to support frames and lenses and create a watertight seal with the face of a diver. The skirt material may be almost transparent, translucent or opaque. Almost transparent skirts provide greater peripheral peripheral vision, although somewhat distorted, and may reduce claustrophobic feelings in some divers, but in some cases light entering through the sides can cause intrusive internal reflections. The skirt also covers the nose, usually by using a nose pouch, so air can be exhaled through the nose into the mask to equalize internal pressure during down and thus avoid possible barotrauma from the enclosed area of ​​the face. The mask that covers the nose should allow the wearer to block the nostrils while equating the pressure in the middle ear. All diving masks have the means to keep them in position, usually elastomeric ropes from the same material to the skirt, but occasionally an extended neoprene bearing with a velcro strap is used. The mask strap is usually wider on the back or separated into the top and bottom straps on the back of the head for stability and comfort.
Some masks have a one-way cleaning valve under the nose to let the water out, but this is no longer common because it is unnecessary and unreliable, and often leaks.
Visual correction
Diving masks can be equipped with recipe lenses for divers that require optical correction to improve vision. Correct ground lens is flat on one side and cemented optically to the inside of the face of the lens mask. This gives the same amount of correction above and below the water level. Bifocal lenses are also available for this application. Some masks are made with removable lenses, and various standard corrective lenses are available that can be mounted. The plastic self-adhesive lens that can be applied to the inside of the mask may fall out if the mask is flooded for significant periods. Contact lenses may be worn under a mask or helmet, but there is some risk of losing them if the mask is dislodged in turbulent water.
Fit
Masks are considered to fit well when sealing comfortably and effectively around the skirt, and provide a good visual field, without suppressing the nose or forehead when used underwater. Low internal volume is considered desirable by freedivers, as fewer breaths are wasted to equalize, and by scuba divers, as there is less tendency to squeeze under the nose due to buoyancy, which becomes uncomfortably fast.
Divers can test whether the mask fits by putting it on their face, without using a strap, and gently inhaling through their nose. If the mask stays on without any help, it indicates that no air is drawn in and that the skirt is enough to touch the facial skin along the mask. Optimal sealing requires that hair strands do not crosses beneath the edge of the seal, as they can provide a way for water to leak into the mask. This is more of a problem with the forehead line than the lower facial hair, as water from above tends to flow into the eye, while the puddles at the bottom are easy to clean by blowing a little air through the nose. Most bearded divers learn to manage a little leak without difficulty, discomfort, or a mustache. Other factors that affect a comfortable fit are enough space for the nose in the nasal pocket, no contact between the rigid mask frame and the bridge of the nose, and no excessive pressure on the forehead. There should be enough space between the mask and face lenses to prevent the lashes from touching the glass when blinking.
Use
The rope can be adjusted to fit the diver's head. Too loosely may not provide an effective seal and masks can be ejected easily, and too tight can cause discomfort or pain. Positioning the correct rope around the back of the head will reduce the risk of discharge and facilitate cleaning.
When entering the water while wearing a mask, the diver may need to manually prevent the impact of water from plucking or crashing the mask. Alternatively, a diver can enter the water with the mask off and then wear it or use an entry method that does not generate a rapid flow of water over the mask. Wearing masks that are pushed to the forehead when out of the water or on the surface increases the risk of masks falling or being thrown off.
To prevent the mask from fog due to condensation on the glass many divers spit into a dry mask before use, spread the saliva around the inside of the dish and rinse with a little water. Salivary residues allow condensation to wet the glass and form a sustainable film, rather than forming droplets. There are commercial products that can be used as an alternative to saliva methods, some of which are more effective and last longer.
Standard care is to rinse inside and outside with clean and clean water after daily use, and let dry from direct sunlight before saving. Ultraviolet light degrades the synthetic material from skirts and frames. A well-maintained mask should last for several years. Rope is the most stressful component and is often the first part to fail, but it can usually be replaced. Inspection of ropes for cracks and tears before use can reduce the risk of failure during diving.
Removal of mask and underwater refitting and clearing are the basic skills that all divers have to learn so they can handle flood and leak or masks that dislodged without panic.
Cleaning mask
It is very common for water to leak into the mask, which can disturb, or interfere with clear vision, and the diver should be able to get rid of water quickly and effectively. Reasons for leakage include poor or fit fit, leaking through head or facial hair, facial muscle movement causing temporary leakage, or impact of an outer object on a mask, which can distort it temporarily, or move it to leak, or in extreme cases, head diver.
The cleaning method differs between half masks, which cover the eyes and nose, and a full face mask, which also covers the mouth. If the mask has a cleaning valve and the strap tension is correct, the diver holds the head so that the valve is at its lowest point and exhaling through the nose. If the mask fits perfectly on the diver's face and the rope is placed correctly, exhaling through the nose will usually push the water out along the bottom edge of the skirt. It may be necessary to press the top of the mask against the face to fix the seal if the diver is rolled to one side. If the match is not perfect, or the strap is too low, the upper edge contact pressure on the forehead may not be sufficient to maintain the seal when the head is upright.
Equalize
Pressure changes during ascent and decline can affect gas spaces in divers and dive equipment. Pressure changes will cause a pressure difference between the gas chamber and the environment which will cause the gas to expand or compress if possible, and inhibit gas to expand or compress to balance the pressure can cause damage to the material or surrounding tissue. by excessive expansion or destruction. Some gas chambers, such as masks, will automatically release excess gas as it expands during ascent, but must be equated during compression decline.
Equity mask is an important skill for all forms of diving. Goggles that do not cover the nose can not be synchronized and not suitable for diving. Masks are equated with exhaling enough air through the nose to provide balanced internal pressure. Any excess will only leak around the skirt. Equating (or cleaning) the ear is necessary to prevent the barotrauma to the middle and inner ear. Some divers need to pinch the closed nostrils as part of their equalization technique, and this should be allowed in the mask skirt design.
Type of diving mask
The initial dive model mask has a single elliptical panel of glass. This mask has a curve in the skirt at the bottom on both sides of the nose, where divers can enter the thumb and forefinger to pinch the nose, while performing Valsalva maneuvers to clean their ears. This design is enhanced by bringing the window closer to the face, reducing the volume of air inside the mask, thus making the mask easier to clean. The window has pieces to be installed around the nose, which is covered by rubber or silicone material from the skirt. This makes it easy to pinch the nose when cleaning the ears.
The next development is a mask with two windows, one for each eye. It can have a window closer to the face than the one-window type, and therefore contains less internal volume for the diver to clean or equalize. These types are often called "low volume masks". Participants in underwater hockey sport are required to use this type double lens mask for their own safety - this sport uses a large piece similar to an ice hockey piece, but an advanced player can snap a fairly high piece from the bottom. when performing an operand that leads to the possibility of accidental chip contact with other players. If a piece touches the lens from a lens mask, it is most likely that it will break the glass and pass through the aperture to hit the face and eyes, but with a twin-lens mask even though the glass can damage the frame will prevent the further passing of the chip.
The latest innovations have resulted in more complex designs, intended to provide additional features:
- Dome double mask. It was invented by HydroOptix. Dome double mask allows a wider field of view and avoids refractive errors in the distance and the size of the perceived object. Underwater curved mask windows make the vision of the diver effectively more hyperopic, or less nearsighted, and the diver must wear special contact lenses to compensate (unless his eyes are shortsighted to the right amount to compensate for precisely refraction in the curved mask window). The vision of the diver will be shortsighted as he lays his head out of the water with contact lenses coming in.
- The "Data Mask", developed by Oceanic, is a half mask with a built-in LCD head-up display featuring various dive and breathing conditions including dive computer functions, depth pressure and tank.
Peralatan terkait
There are several special types of headgear or dive outfits:
- full face dive masks - often worn by working divers who require underwater verbal communication skills.
- Light diving helmet - usually worn by divers using submerged equipment provided on the surface.
- Copper hat - part of ancient standard wet suit.
- a fluid-filled mask - the need to balance internal pressure in the mask by blowing air through the nose reduces the capacity of the diver to dive away. Masks or swim goggles with high-powered lenses (40-200 diopters) have been developed in this view: they are filled with water or saline.
See also
- Underwater vision
References
Further reading
External links
- Deep Ocean Diving's Ocean Science - Explanation of underwater vision physics.
Source of the article : Wikipedia
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