A projective optical metrology system comprising: - a light target formed by a first number of light sources (4a-4c) having a pre-set spatial arrangement; - an optical unit comprising an optoelectronic image sensor comprising a detection surface, the optical unit being configured for receiving a light signal (R 1, R 2) coming from said light target and for defining two different optical paths for the light signal towards said optoelectronic image sensor; and - an electronic processing unit coupled to the optoelectronic image sensor; characterized in that the two optical paths are configured such that the light signal forms on the optoelectronic image sensor at most one image (I 1;I 2) of the light target, the electronic processing unit being configured to process said at most one image and to determine at least one quantity indicating the mutual arrangement of the light target and of the optical unit; and wherein the two optical paths, the light target and the detection surface are configured such that: - when the light target is set, from the optical unit, at a distance comprised in a first interval of distances ([D x, d min]), the light signal forms on the detection surface, through a first optical path of said two optical paths, a first image (I 1), on the of basis of which the electronic processing unit is able to determine a number of maxima of light intensity equal to said first number; - when the light target is set, from the optical unit, at a distance that falls outside said first interval of distances ([D x, d min]), the light signal alternatively does not form, through said first optical path, any image on the detection surface, or else forms, through said first optical path, an image on the basis of which the electronic processing unit is not able to determine a number of maxima of light intensity equal to said first number; - when the light target is set, from the optical unit, at a distance comprised in a second interval of distances ([D max, d x [), the light signal forms on the detection surface, through a second optical path of said two optical paths, a second image (I 2), on the basis of which the electronic processing unit is able to determine a number of maxima of light intensity equal to said first number; and - when the light target is set, from the optical unit, at a distance that falls outside said second interval of distances ([D max, d x [), the light signal alternatively does not form, through said second optical path, any image on the detection surface, or else forms, through said second optical path, an image on the basis of which the electronic processing unit is not able to determine a number of maxima of light intensity equal to said first number. - a light target formed by a first number of light sources (4a-4c) having a pre-set spatial arrangement; - an optical unit comprising an optoelectronic image sensor comprising a detection surface, the optical unit being configured for receiving a light signal (R 1, R 2) coming from said light target and for defining two different optical paths for the light signal towards said optoelectronic image sensor; and - an electronic processing unit coupled to the optoelectronic image sensor; - when the light target is set, from the optical unit, at a distance comprised in a first interval of distances ([D x, d min]), the light signal forms on the detection surface, through a first optical path of said two optical paths, a first image (I 1), on the of basis of which the electronic processing unit is able to determine a number of maxima of light intensity equal to said first number; - when the light target is set, from the optical unit, at a distance that falls outside said first interval of distances ([D x, d min]), the light signal alternatively does not form, through said first optical path, any image on the detection surface, or else forms, through said first optical path, an image on the basis of which the electronic processing unit is not able to determine a number of maxima of light intensity equal to said first number; - when the light target is set, from the optical unit, at a distance comprised in a second interval of distances ([D max, d x [), the light signal forms on the detection surface, through a second optical path of said two optical paths, a second image (I 2), on the basis of which the electronic processing unit is able to determine a number of maxima of light intensity equal to said first number; and - when the light target is set, from the optical unit, at a distance that falls outside said second interval of distances ([D max, d x [), the light signal alternatively does not form, through said second optical path, any image on the detection surface, or else forms, through said second optical path, an image on the basis of which the electronic processing unit is not able to determine a number of maxima of light intensity equal to said first number.