A ray shield, also known as an energy shield was a specialized type of deflector shield used to absorb radiation and raw energy, as opposed to particle shields, which repelled solid objects. Employed in both the time of the Galactic Republic and the Galactic Empire, it functioned by deflecting or scattering energy beams. However, ray shields did not allow physical objects through them completely unscathed, imparting a deadly electric shock. As such they could be used in traps.
Ray shields were generated by a projector and were commonly used in conjunction with the more basic particle shields, which repelled solid obstacles such as micro-meteroids and space debris. While particle shields protected the ship's physical hull, ray shielding was primarily designed to protect its occupants, electronics and cargo from realspace magnetic and that would otherwise quickly fry them. Although a low-level energy setting was more than enough to achieve this, military starships would boost up their ray shields for defensive purposes as well, to deflect laser bolts and other focused energy weaponry. Prolonged operation in high-energy settings could easily overload a generator, requiring highly specialized tech.
Jedi Master Obi-Wan Kenobi, Jedi Knight Anakin Skywalker, and Supreme Chancellor Sheev Palpatine were once caught in a ray shield trap on the Invisible Hand, set by General Grievous. Kenobi lamented that they were too smart to be caught in such an obvious trap and were soon surrounded by droids and brought to the bridge to meet Grievous.
The impregnable prison known as the Spire on the planet Stygeon Prime was fortified by ray shields.
The reactor shaft of the Empire's original Death Star superweapon was ray shielded, such that only proton torpedoes would start the chain reaction necessary to destroy it.
Ray shields avoided the problem of certain shields in that they could be extended to the ground without those inside of them running out of air. However, they were only considered useful in certain applications because they allowed through objects such as missiles and torpedoes.