The invention concerns a biometric capture optical device (1) comprising a prismatic optical element (2) having one side (4) appearing in a window (3) to provide a support surface for a bodily limb and illuminating means (6) designed to illuminate the side (4) from within the element (2) and form by total reflection a biometric image of the bodily limb; in addition, luminous information display means are located beneath the element (2) opposite the window (3) so as, in the absence of the bodily limb on the side (4), to transmit, without total reflection, through the window (3) a luminous information image visible from outside (15).