Abstract: A method includes the following (1) detecting light returned from a target with an imaging sensor during a first frame exposure time period to capture a first image when a first illumination light is projected towards the target; (2) processing the first image to determine the light intensity of a second illumination light; (3) detecting light returned from the target with the imaging sensor during a second frame exposure time period to capture a second image when the second illumination light is projected towards the target; and (4) decoding a barcode in the second image. The light intensity of the first illumination light changes with time at least during part of the first frame exposure time period.