A driver apparatus is provided for controlling a
light source array comprising at least first and second light sources, the
light source array used for illuminating a scan region on a target object, wherein light reflected from said target object is captured by a
detector. The driver apparatus comprises a single
integrated circuit comprising
processing means for
processing image data received from the
detector, a switching array comprising at least first and second switches for switching the respective first and second light sources, and a
current source for controlling the flow of current through the light sources. In this way the LED switching circuitry that controls an
LED array is placed on the same
integrated circuit (i.e. monolithic circuit) as the analogue
processing circuitry that processes the image data, with the
current source controlling the flow of current through the LEDs in the
LED array. The
current source has the
advantage of avoiding rapid changes or slope discontinuities in the current flowing through the LEDs, which would otherwise cause unwanted transient signals. A shunt path comprising a switching device may be provided in parallel with the
LED array and switching array. The shunt path has the
advantage of enabling the switching sequence from one LED to another to be controlled such that a substantially
constant current is drained from the supply (subject to any differences in the inherent current drawn by the Red, Green and Blue LEDs, respectively).