Deflector shield
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A deflector shield is a fictional technology commonly found in science fiction. Typically, deflector shields (often referred to as simply "shields") are some form of energy field designed to deflect kinetic or electromagnetic energy. The field is projected along the surface of, or into the space around, a starship, space station, planet, moon, or building. Some are small enough for a person to wear in combat, such as in the Dune universe.
The concept goes back at least as far as the 1920s, in the works of E.E. 'Doc' Smith and others; and William Hope Hodgson's The Night Land (1912) has the Last Redoubt, in which the remnants of humanity shelter, protected by something very like one. Although fictional, deflector shields have some resemblance to real devices such as magnetic field generators, or better yet, plasma windows.
The phrase "Shields Up!" which saw widespread use in Star Trek, probably had its origin in classical warfare, when infantry would raise their shields to defend against incoming arrows or other projectiles. The order would be given when it was time for the solder to raise his shield from the carry position.
The abilities and exact functionality of deflector shields vary; in some works (such as in the Star Trek universe), deflector shields can stop both energy beams (e.g. phasers) and physical projectiles, both natural and artificial; in others, such as the Star Wars universe, there are multiple types of deflector shields—so-called ray shields which are designed to stop energy beams (such as laser and blaster weapons), and particle shields which are designed to stop kinetic projectiles, missiles, bombs, etc.
Deflector shields usually work by absorbing or dissipating the energy of the incoming attack; prolonged exposure to such attacks weakens the shield and eventually results in the shield's collapse, making the ship's hull (or building's walls, or planet's surface) vulnerable to attack. Larger deflector shield systems, or those powered by bigger energy sources, can absorb/dissipate more damage before failing -- so that larger starships, for example, can mount much stronger shields than a small, single-person starfighter, much in the way that a sea-going battleship has much thicker armor than a tiny patrol boat.
Personal shield generators, whilst providing great protection to conventional weaponry, often prove vulnerable to slow moving projectiles as in the spear thrown by Rogue Trooper in 2000 AD or the dagger thrown by Colonel Jack O'Neill to penetrate Goa'uld shields in the Stargate universe. In the Dune Universe the use of Holtzman effect personal shield generators is risky, for hits by laser weapons (lasguns) can trigger a large atomic explosion.
In some science fiction works, a shield does not deflect attacks but rather absorbs them, dissipating the energy of the attack. These shields are most commonly called "screens", "defensive shielding", or even more common, simply "shields."
Other names for a deflector shield include "deflector screen", "defensive screen", "screen", or "defensive shielding".
Deflector shields in Star Trek
Deflector shields in Halo: Combat Evolved
In the video game Halo: Combat Evolved, deflector shields are worn by certain Covenant personnel, placed as stationary defences (much like a physical shield), and equipped by the Human Spartan-IIs as a core component of their MJOLNIR powered armor. There are two main types of shielding. The first (and most common) type of shielding generates a visible energy field. The field generated, and is usually worn like a buckler or placed as a static defence. The second form of shielding is the personal body shield.
Deflector shields in Stargate
Shields are seen many times throughout the Stargate universe, the most powerful usually being Ancient shielding followed by Asgard shields.ja:シールド (サイエンス・フィクション)