An optical system for detecting a presence of a living biological element, comprising: a first and a second pairs of light sources (1, 2) that emit pulsed electromagnetic radiation with an emission band located in a near-infrared zone of the electromagnetic spectrum; a first and a second photodetectors (4a, 4b) with an absorption band located in the near-infrared zone of the electromagnetic spectrum, for detecting the pulsed radiation transmitted and reflected on the biological element, on a basis of the pulsed radiation emitted by the first and second pairs of light sources (1, 2); a third pair of light sources that emit pulsed electromagnetic radiation with an emission band located in a near-ultraviolet zone of the electromagnetic spectrum; a third photodetector with an absorption band located in the near-ultraviolet zone of the electromagnetic spectrum, for detecting the pulsed radiation reflected on the biological element, on a basis of the pulsed radiation emitted by the third pair of light sources; a control unit (8(c)), connected to the pairs of light sources (1, 2, 3) and to the photodetectors (4a, 4b, 5), adapted to govern a plurality of electrical functions that feed the pairs of light sources (1, 2, 3); said electrical functions being comprised of periodic alternate electrical signals, so that each pair of light sources (1, 2, 3) emits on an alternate basis interpret the pulsed radiation transmitted and reflected on the biological element and detected by the photodetectors (4a, 4b, 5) and a processing unit (8(d)), connected to the control unit (8(c)), configured to determine if the biological element is a living biological element, on a basis of the radiation interpreted by the control unit (8(c)). a first and a second pairs of light sources (1, 2) that emit pulsed electromagnetic radiation with an emission band located in a near-infrared zone of the electromagnetic spectrum; a first and a second photodetectors (4a, 4b) with an absorption band located in the near-infrared zone of the electromagnetic spectrum, for detecting the pulsed radiation transmitted and reflected on the biological element, on a basis of the pulsed radiation emitted by the first and second pairs of light sources (1, 2); a third pair of light sources that emit pulsed electromagnetic radiation with an emission band located in a near-ultraviolet zone of the electromagnetic spectrum; a third photodetector with an absorption band located in the near-ultraviolet zone of the electromagnetic spectrum, for detecting the pulsed radiation reflected on the biological element, on a basis of the pulsed radiation emitted by the third pair of light sources; a control unit (8(c)), connected to the pairs of light sources (1, 2, 3) and to the photodetectors (4a, 4b, 5), adapted to govern a plurality of electrical functions that feed the pairs of light sources (1, 2, 3); said electrical functions being comprised of periodic alternate electrical signals, so that each pair of light sources (1, 2, 3) emits on an alternate basis interpret the pulsed radiation transmitted and reflected on the biological element and detected by the photodetectors (4a, 4b, 5) and a processing unit (8(d)), connected to the control unit (8(c)), configured to determine if the biological element is a living biological element, on a basis of the radiation interpreted by the control unit (8(c)).