The present invention relates to a detection system for detecting movement of a movable object. The detection system comprises a light source (S) for emitting light, a reflecting unit (8) being arranged in functional connection with the movable object (6) and being adapted for reflecting the emitted light, at least one detector (D1 to D4) for detecting the reflected light and outputting detection signals for determining the movement of the movable object, an analogue-to-digital converter which includes at least one current source for obtaining a digital signal, and a common mode controller for outputting at least one common mode signal for controlling the at least one current source, wherein the digital signal which is indicative of the movement of the movable object in a predetermined direction being based on the output signal of the at least one detector and the at least one common mode signal. The present invention also concerns a method of detecting movements of a movable object, as well as an integrated circuit having implemented therein the detection system.