A method of illuminating objects using adaptively controlled mixing of spectral illumination energy to form and detect digital images of objects at a POS. The method comprises providing, at a POS environment, a digital image capture and processing system having a system housing with an imaging window, and an area-type illumination and imaging station disposed within said system housing, for projecting a coextensive area-type illumination and imaging field (i.e. zone) through said imaging window into a 3D imaging volume during object illumination and imaging operations. As the object is moved through the 3D imaging volume, its motion is automatically detected, and signals indicative of said detected object motion are generated. In response to the generated signals, a first field of visible illumination is produced from an array of visible LEDs, simultaneously with a second field of invisible illumination from a array of infrared (IR) LEDs. These first and second fields of illumination spatially overlap and intermix with each other to produce a composite wide-area illumination beam that is at least substantially coextensive with the FOV. During object illumination and imaging operations, the relative power ratio (VIS/IR) of these fields of visible illumination and invisible illumination is adaptively controlled as one or more digital images of the illuminated object are formed and detected, captured and buffered, and ultimately processed so as to read one or more 1D and/or 2D code symbols graphically represented in the digital images.