An LED based light source unit for an endoscopic imaging system produces illumination for a camera through an endoscope. The light source unit includes an array of LEDs mounted to a thermally conductive substrate. The light source unit is integrated into the proximal end of an endoscope and coupled directly to the optical fibers running to the tip of the endoscope. A plurality of such light source units may be integrated into the housing of an endoscope. Light emitted from each light source unit is directed to a distinctive section of the endoscope's tip and a doctor may control light output of each individual light source unit during a surgery.