A photosensitive chip, including first and second sets of photosensors aligned in a Y direction and separated in a perpendicular X direction and third and fourth sets of photosensors aligned in the Y direction and separated in the X direction. The first and third sets are aligned in the X direction. The second and fourth sets are aligned in the X direction. The first and third sets are offset in the Y direction from the second and fourth sets by a distance about equal to a length of a photosensor divided by the number of sets. A time interval between activation of two sequential photosensors from the first through fourth sets of photosensors is substantially equal to the time period of a scan line for the first through fourth sets of photosensors divided by the number of photosensors in the first through fourth sets of photosensors.