A marking device comprising: a first marker including a first optical system having a first focal point , the first marker being configured to concentrate a first light (L1) onto a first area of a non-planar portion of a medium to perform marking on the first area , the non-planar portion including a plurality of areas including the first area and a second area ; the marking device being characterised by : a second marker including a second optical system having a second focal point , the second marker being configured to concentrate a second light (L2) onto the second area of the non-planar portion of the medium to perform the marking on the second area , the second focal point of the second optical system being different from the first focal point of the first optical system in a direction parallel to a central axis of the first optical system , and further characterized in that the first marker and the second marker are arranged in such a way that the first area does not overlap with the second area and in that the marking device comprises a controller configured to control the first marker and the second marker such that the first marker performs the marking in parallel with the second marker . a first marker including a first optical system having a first focal point , the first marker being configured to concentrate a first light (L1) onto a first area of a non-planar portion of a medium to perform marking on the first area , the non-planar portion including a plurality of areas including the first area and a second area ; the marking device being characterised by : a second marker including a second optical system having a second focal point , the second marker being configured to concentrate a second light (L2) onto the second area of the non-planar portion of the medium to perform the marking on the second area , the second focal point of the second optical system being different from the first focal point of the first optical system in a direction parallel to a central axis of the first optical system , and further characterized in that the first marker and the second marker are arranged in such a way that the first area does not overlap with the second area and in that the marking device comprises a controller configured to control the first marker and the second marker such that the first marker performs the marking in parallel with the second marker . a second marker including a second optical system having a second focal point , the second marker being configured to concentrate a second light (L2) onto the second area of the non-planar portion of the medium to perform the marking on the second area , the second focal point of the second optical system being different from the first focal point of the first optical system in a direction parallel to a central axis of the first optical system , and further characterized in that the first marker and the second marker are arranged in such a way that the first area does not overlap with the second area and in that the marking device comprises a controller configured to control the first marker and the second marker such that the first marker performs the marking in parallel with the second marker . <EOS>