A method includes the following: (1) projecting a light pattern towards a target object; (2) detecting light returned from the target object through an imaging lens arrangement with an imaging sensor to capture a first image with changes in the position of the focus plane of the imaging lens arrangement; (3) processing the first image to determine an optimized position of the focus plane of the imaging lens arrangement; (4) detecting light returned from the target object with the imaging sensor to capture a second image when the position of the focus plane of the imaging lens arrangement is maintained at the optimized position; and (5) decoding a barcode in the second image.