I've provided a cross section from a phaser array element from DITL to aid my question:
The emitter is apparently the flat, horizontal part at the top. The problem is that I've never understood how the beam is directed from a phaser array. Ball turrets clearly have an opening where the phaser beam will exit, and they can swivel around to almost any angle. The arrays, however, are composed of linked segments that seem to be fixed to the hull. Sometimes in TNG and DS9, we are given close-up shots of the arrays, and there is no indication of the existence of any kind of directional controls. The segments themselves clearly don't move; oftentimes, it even looks like the phasers just shoot out of the metal panels.
If there is no mechanical method of directing/aiming the phaser beams, how is aiming accomplished?