A system for optical inspection of a substrate , the system comprising: • an illumination device comprising a light source (S) for generating at least one incident light beam presenting at least a first wavelength directed onto an exposed surface of the substrate to define an inspection area (I) of the substrate , defects present on, or close to, the surface of the substrate provoking the emission of radiations at said first wavelength and/or radiations presenting at least a second wavelength different from said at least first wavelength; • a support to receive the substrate and to position the substrate relatively to the illumination device, the support and the light source (S) being movable relatively to each other according to a scanning direction (SD); • a detection device comprising a collector for collecting at least a portion of the radiations at said first wavelength and/or at said second wavelength originating from a detection area (D) of the substrate and a detector optically associated to the collector , the detector presenting a sensing surface for capturing the collected radiations, the detection area (D) corresponding to the optical conjugate of the sensing surface by the collector , the detection device providing a measurement signal representing the variation in intensity of the collected radiations as the substrate is moved along the scanning direction (SD); the system being characterized in that the system is based on a dark field configuration, ensuring that the specular reflections of the incident light beam on the substrate are not collected by the collector and is configured to position the inspection area (I) ahead of at least a portion of the detection area (D), with respect to the scanning direction (SD), while the inspection zone (I) scans the exposed surface of the substrate , such that a part of the substrate having left the inspection area (I) due to the relative movement of the support and the light source (S) will still be in the detection area (D) for some time. • an illumination device comprising a light source (S) for generating at least one incident light beam presenting at least a first wavelength directed onto an exposed surface of the substrate to define an inspection area (I) of the substrate , defects present on, or close to, the surface of the substrate provoking the emission of radiations at said first wavelength and/or radiations presenting at least a second wavelength different from said at least first wavelength; • a support to receive the substrate and to position the substrate relatively to the illumination device, the support and the light source (S) being movable relatively to each other according to a scanning direction (SD); • a detection device comprising a collector for collecting at least a portion of the radiations at said first wavelength and/or at said second wavelength originating from a detection area (D) of the substrate and a detector optically associated to the collector , the detector presenting a sensing surface for capturing the collected radiations, the detection area (D) corresponding to the optical conjugate of the sensing surface by the collector , the detection device providing a measurement signal representing the variation in intensity of the collected radiations as the substrate is moved along the scanning direction (SD); <EOS>