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 at least a first slit-frame-image and a second slit-frame-image; (3) determining an optimized position of the imaging lens arrangement; (4) detecting light returned from the target object with the imaging sensor to capture an image of a barcode when the imaging lens arrangement is maintained at the optimized position; and (5) processing the image of the barcode to decode the barcode. In the method, determining the optimized position includes processing at least the first slit-frame-image and the second slit-frame-image.