An air carrier pilot on a takeoff roll at MDW reported a near miss with a helicopter; which delayed its takeoff and then turned toward the reporter's runway during its departure.

Narrative

As we taxied I heard the Tower Controller tell a helicopter to change to Departure frequency. I thought it was strange as the helicopter had not taken off yet. Then we were cleared on to hold. We got on the runway and stopped. As the preceding aircraft cleared the runway; we were cleared for takeoff. We began the takeoff roll as normal. I called 80 knots and shortly after called V1 at 111 KTS; which was five knots prior to V1. As we were rolling down the runway I noticed the helicopter lifting off; but he seemed to be hovering near the edge of the runway; but not crossing it. Then as we got close to rotation speed; which I think was around 135 KTS I saw the helicopter head towards our runway. The Captain slightly delayed the rotation as to not pull up right into the helicopter; but the runway in front of us was rapidly shrinking. The Captain slowly pulled up and tried to stay underneath the helicopter without hitting him. I stayed focused on looking out front to make sure we were high enough to clear the fence and houses in front of us. The helicopter made a turn to the left to put him parallel to our heading and started to move away from the runway. I believe we were within 50 FT of the helicopter; but that is just an estimate. A few seconds later we were clear of the conflict and we continued our profile as normal.