SRD:Force Screen

You create an invisible mobile disk of force that hovers in front of you. The force screen provides a +4 shield bonus to Armor Class (which applies against incorporeal touch attacks, since the force screen is a force effect). Since it hovers in front of you, the effect has no armor check penalty associated with it.

Augment: For every 4 additional power points you spend, the shield bonus to Armor Class improves by 1.