Objects associated with targets to be read by image capture are detected without any additional hardware in an imaging module. Return light is captured over a field of view of the module. Images are processed, during an object detection mode, to determine their image brightness from the captured return light. Illumination is emitted from an illumination light assembly at a first power level to determine a first image brightness from a first processed image, and at a different, reduced, second power level to determine a second image brightness from a second processed image. An object is determined to be in the field of view when a difference between the first image brightness and the second image brightness equals or exceeds a detection threshold value.