1. A variable focus imaging lens assembly for an imaging system of an imaging-based bar code reader for imaging and decoding a target bar code, the imaging system generating image frames of a field of view of the imaging system and including an imaging sensor array and a decoder for decoding an image of the target bar code, the variable focus imaging lens assembly comprising: a lens assembly focusing light from the field of view onto the sensor array, the lens assembly including a lens movable along a path of travel; a drive mechanism driving the movable lens from a predetermined position along the path of travel; an automatic focusing system: energizing the drive mechanism and imaging system to move the movable lens from the predetermined position along its path of travel and generate a series of image frames; analyzing one or more image frames of the series of image frames to determine a region of interest, the region of interest including an image of a target bar code; analyzing the region of interest in subsequent image frames of the series of image frames to determine an amount of blurring in each image frame; selecting an image frame from the subsequent image frames of the series of image frames having an amount of blurring less than a predetermined threshold; and utilizing the decoder to decode the image of the target bar code in the selected image frame.