LOSS OF SEPARATION BTWN A B737 ON TKOF ROLL AND A C210 TAXIING OPPOSITE DIRECTION ON THE SAME RWY.

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OPERATING FROM PHL TO ORD; I WAS THE CAPT PERFORMING NON FLYING DUTIES. THE FO FLEW THE ACFT FROM TKOF TO LNDG. AFTER WE RECEIVED AND ACKNOWLEDGED TKOF CLRNC FROM PHL TWR; I RAN THE WINDOW WIPERS MOMENTARILY TO CHECK DOWN THE RWY. AS WE STARTED OUR TKOF ROLL; I OBSERVED WHAT APPEARED TO BE ONE RWY CENTERLINE LIGHT BRIGHTER THAN THE OTHERS ABOUT 3/4 OF THE WAY DOWN THE RWY. BOTH THE FO AND A COCKPIT JUMPSEAT PLT DID NOT NOTICE THE LIGHT. THE RWY ITSELF APPEARED CLR. TKOF ROLL WAS NORMAL EXCEPT GUSTY WINDS CAUSED THE AIRSPEED INDICATOR TO HANG UP/FLUCTUATE TWICE PRIOR TO V1 AND ONCE AT V1. AT ROTATION; I CALLED ROTATE AND AS THE FO BEGAN HIS ROTATION ALL THREE OF US OBSERVED WHAT APPEARED TO BE A CESSNA 172 ACFT TAXIING TOWARD US; JUST AHEAD OF US ON RWY 9L AND THEN THE CESSNA APPARENTLY ATTEMPTED TO VEER TO HIS R AS WE PASSED OVER IT. THE FO INCREASED ROTATION AND INITIAL PITCH ALT TO GAIN GREATER VERTICAL CLRNC. WE ESTIMATE VERTICAL CLRNC OVER THE CESSNA BETWEEN 10 AND 100 FT. WE RPTED THE INCIDENT TO PHL TWR AND THEN CONTACTED DISPATCH AND FLT DUTY MANAGER. CONTRIBUTING FACTORS WERE RAIN; MIST; TWILIGHT LIGHTING DUE TO LOW THICK CLOUDS; GUSTY WINDS AND CESSNA COLORS: LIGHT TAN OR YELLOW.