A sensor system for inspecting oil, which comprises a micromechanical cell formed by a first member and a second member, said first and second members defining a cavity, the micromechanical cell being configured for allowing the entrance of oil within said cavity and the outcome of oil from said cavity through respective inlet and outlet, the sensor system comprising inside said micromechanical cell: - a first transparent protective means configured to isolate the inner part of said first member from said cavity to be occupied with oil; - a second transparent protective means configured to isolate the inner part of said second member from said cavity to be occupied with oil; - a light source disposed in said first member and configured to emit incoherent light towards said oil disposed within said cavity; - an image sensor disposed in said second member situated on the opposite side of the cavity with respect to said first member and configured to capture a sequence of images of the oil disposed within said cavity; characterized in that the sensor system further comprises: - an opaque plate disposed between said light source and said first transparent protective means, said plate having a pin-hole configured to permit the passage of illumination towards said cavity to be occupied with oil, said pin-hole being located at a first distance from a focussing plane defined by said cavity, said image sensor being located at a second distance from said focussing plane defined by said cavity; and - a diffuser disposed between said light source and said plate defining the pin-hole, said diffuser being disposed adjacent to the plate, said diffuser being configured to provide homogeneous lighting to said cavity. the sensor system comprising inside said micromechanical cell: - a first transparent protective means configured to isolate the inner part of said first member from said cavity to be occupied with oil; - a second transparent protective means configured to isolate the inner part of said second member from said cavity to be occupied with oil; - a light source disposed in said first member and configured to emit incoherent light towards said oil disposed within said cavity; - an image sensor disposed in said second member situated on the opposite side of the cavity with respect to said first member and configured to capture a sequence of images of the oil disposed within said cavity; - a first transparent protective means configured to isolate the inner part of said first member from said cavity to be occupied with oil; - a second transparent protective means configured to isolate the inner part of said second member from said cavity to be occupied with oil; - a light source disposed in said first member and configured to emit incoherent light towards said oil disposed within said cavity; - an image sensor disposed in said second member situated on the opposite side of the cavity with respect to said first member and configured to capture a sequence of images of the oil disposed within said cavity; characterized in that the sensor system further comprises: - an opaque plate disposed between said light source and said first transparent protective means, said plate having a pin-hole configured to permit the passage of illumination towards said cavity to be occupied with oil, said pin-hole being located at a first distance from a focussing plane defined by said cavity, said image sensor being located at a second distance from said focussing plane defined by said cavity; and - a diffuser disposed between said light source and said plate defining the pin-hole, said diffuser being disposed adjacent to the plate, said diffuser being configured to provide homogeneous lighting to said cavity. - an opaque plate disposed between said light source and said first transparent protective means, said plate having a pin-hole configured to permit the passage of illumination towards said cavity to be occupied with oil, said pin-hole being located at a first distance from a focussing plane defined by said cavity, said image sensor being located at a second distance from said focussing plane defined by said cavity; and - a diffuser disposed between said light source and said plate defining the pin-hole, said diffuser being disposed adjacent to the plate, said diffuser being configured to provide homogeneous lighting to said cavity.