An image capture instrument implements an addition of accumulation signals for photodetectors which are adjacent within a row of photodetectors. Segments are defined in the row with one and the same common length of segment, while being progressively offset by an offset length which is constant. The accumulation signals are added together for photodetectors which belong to one and the same segment. The offset length is less than the segment length, and greater than half said segment length. Artifacts in the image captured, which are due to spectrum aliasing, are thus decreased. The signal-to-noise ratio of the image is increased.