A projective optical metrology system comprising: - a light target comprising a plurality of light sources (4a-4c) having a pre-set spatial arrangement; - an optoelectronic image sensor; - an optical unit configured for receiving a light signal (R 1, R 2) coming from the light target and for defining two different optical paths for the light signal towards the optoelectronic image sensor, the two optical paths being such as to cause simultaneous formation on the optoelectronic image sensor of at least two images (I 1, I 2) of the light target; wherein the optical unit further comprises a receiving optical element configured for receiving the light signal (R 1, R 2) coming from the light target; and wherein both of the two optical paths extend towards the optoelectronic image sensor starting from the receiving optical element; the optical unit further comprising: - a first optical circuit having a first front principal plane (P 1; P 42a),a first rear principal plane (P 1; P 42b), and a first rear effective focal length (f 1; f e1), and defining a first optical path of said two optical paths; - a second optical circuit having a second front principal plane (P 2; P 44a), a second rear principal plane (P 2; P 44b), and a second rear effective focal length (f 2; f e2), and defining a second optical path of said two optical paths; and wherein the first and second front principal planes are set apart from the receiving optical element, respectively, by a first distance (d c +d 1) and a second distance (d c +d 2) different from one another and measured, respectively, along the first and second optical paths; and wherein the first and second rear principal planes are set apart from the optoelectronic image sensor, respectively, by a third distance (d 3) and a fourth distance (d 4), said third and fourth distances being measured, respectively, along the first and second optical paths and being, respectively, a function of the first and second rear effective focal lengths (f 1, f 2; f e1, f e2); and wherein the optoelectronic sensor comprises a detection surface, and wherein the light target, the detection surface, and the first and second rear effective focal lengths (f 1, f 2; f e1, f e2) are such that, when the light target is set at a first distance (D prog) from the optical unit, both of the two images (I 1, I 2) are contained within the detection surface; - the projective optical metrology system further comprising an electronic processing unit coupled to the optoelectronic image sensor and configured for determining, for each of said two images, a number of maxima of light intensity equal to the number of light sources of the light target, and to determine, on the basis of the position of said numbers of maxima for said two images, a plurality of different quantities indicating the position and attitude of the light target with respect to the optical unit. - a light target comprising a plurality of light sources (4a-4c) having a pre-set spatial arrangement; - an optoelectronic image sensor; - an optical unit configured for receiving a light signal (R 1, R 2) coming from the light target and for defining two different optical paths for the light signal towards the optoelectronic image sensor, the two optical paths being such as to cause simultaneous formation on the optoelectronic image sensor of at least two images (I 1, I 2) of the light target; - a first optical circuit having a first front principal plane (P 1; P 42a),a first rear principal plane (P 1; P 42b), and a first rear effective focal length (f 1; f e1), and defining a first optical path of said two optical paths; - a second optical circuit having a second front principal plane (P 2; P 44a), a second rear principal plane (P 2; P 44b), and a second rear effective focal length (f 2; f e2), and defining a second optical path of said two optical paths; and wherein the first and second front principal planes are set apart from the receiving optical element, respectively, by a first distance (d c +d 1) and a second distance (d c +d 2) different from one another and measured, respectively, along the first and second optical paths; and wherein the first and second rear principal planes are set apart from the optoelectronic image sensor, respectively, by a third distance (d 3) and a fourth distance (d 4), said third and fourth distances being measured, respectively, along the first and second optical paths and being, respectively, a function of the first and second rear effective focal lengths (f 1, f 2; f e1, f e2); and wherein the optoelectronic sensor comprises a detection surface, and wherein the light target, the detection surface, and the first and second rear effective focal lengths (f 1, f 2; f e1, f e2) are such that, when the light target is set at a first distance (D prog) from the optical unit, both of the two images (I 1, I 2) are contained within the detection surface; - the projective optical metrology system further comprising an electronic processing unit coupled to the optoelectronic image sensor and configured for determining, for each of said two images, a number of maxima of light intensity equal to the number of light sources of the light target, and to determine, on the basis of the position of said numbers of maxima for said two images, a plurality of different quantities indicating the position and attitude of the light target with respect to the optical unit.