1. An apparatus for line-scan imaging, the apparatus comprising: a single 2D array of light-sensitive detector elements configured to detect light from a target scene with 3D topography to be imaged, the 2D array divided into a plurality of sub-arrays, each of the sub-arrays being a line-scan imager; and an electrical circuit configured to determine a correction for range-dependent parallax on a detector element-by-detector element basis based on detector element values from at least two rows of parallax detecting detector elements from among the single 2D array to enable images captured by the sub-arrays to be co-aligned with each other.