1. A computing device comprising: a first imaging engine integrating in a single unit separate and apart from said computing device at least one illumination source and an image sensor for impinging an image thereon and outputting a first plurality of signals corresponding to the image impinged on the image sensor; a second imaging engine integrating in a single unit separate and apart from said computing device at least one illumination source and an image sensor for impinging an image thereon and outputting a second plurality of signals corresponding to the image impinged on the image sensor; switching circuitry for operatively switching between the first and second imaging engines; and a processor for controlling the switching circuitry for receiving one of the first and second plurality of signals.