Optical component (100; 500; 600A; 600B) for an attenuated total reflection multispectral imaging device, characterised in that it comprises a support substrate (110; 510) and at least two planar waveguides (120 1, 120 2, 120 3; 520 1, 520 2, 520 3), and in that: - each of the planar waveguides (120 1, 120 2, 120 3; 520 1, 520 2, 520 3) extends in a respective plane, with said respective planes parallel to each other and parallel to a plane of the optical component; - the planar waveguides (120 1, 120 2, 120 3; 520 1, 520 2, 520 3) and the support substrate (110; 510) are superimposed together along an axis orthogonal to the plane of the optical component, with the support substrate which covers the planar waveguides; - each of the planar waveguides comprises at least one diffraction grating (130 1, 130 2, 130 3), to extract light out of said planar waveguide; - at least two of the planar waveguides have their respective diffraction gratings (130 1, 130 2, 130 3) which have values of the average pattern distribution pitch which are distinct from each other; - the support substrate (110; 510) comprises, on one side opposite the planar waveguides (120 1, 120 2, 120 3; 520 1, 520 2, 520 3), a face configured to form an exchange interface with a sample (30, 30') and to be incident to the light extracted from the planar waveguides (120 1, 120 2, 120 3; 520 1, 520 2, 520 3); and - an exit face (113; 513; 613A; 613B) of the optical component (100; 500; 600A; 600B) corresponds to a lateral face of the support substrate (110; 510) arranged so that the light extracted from the planar waveguides (120 1, 120 2, 120 3; 520 1, 520 2, 520 3) and reflected by total reflection in the support substrate (110; 510) at the face configured to form the exchange interface emerges from the optical component (100; 500; 600A; 600B) through this exit face (113; 513; 613A; 613B). - each of the planar waveguides (120 1, 120 2, 120 3; 520 1, 520 2, 520 3) extends in a respective plane, with said respective planes parallel to each other and parallel to a plane of the optical component; - the planar waveguides (120 1, 120 2, 120 3; 520 1, 520 2, 520 3) and the support substrate (110; 510) are superimposed together along an axis orthogonal to the plane of the optical component, with the support substrate which covers the planar waveguides; - each of the planar waveguides comprises at least one diffraction grating (130 1, 130 2, 130 3), to extract light out of said planar waveguide; - at least two of the planar waveguides have their respective diffraction gratings (130 1, 130 2, 130 3) which have values of the average pattern distribution pitch which are distinct from each other; - the support substrate (110; 510) comprises, on one side opposite the planar waveguides (120 1, 120 2, 120 3; 520 1, 520 2, 520 3), a face configured to form an exchange interface with a sample (30, 30') and to be incident to the light extracted from the planar waveguides (120 1, 120 2, 120 3; 520 1, 520 2, 520 3); and - an exit face (113; 513; 613A; 613B) of the optical component (100; 500; 600A; 600B) corresponds to a lateral face of the support substrate (110; 510) arranged so that the light extracted from the planar waveguides (120 1, 120 2, 120 3; 520 1, 520 2, 520 3) and reflected by total reflection in the support substrate (110; 510) at the face configured to form the exchange interface emerges from the optical component (100; 500; 600A; 600B) through this exit face (113; 513; 613A; 613B).