Surface sensing device comprising • a basis, • a probe head for establishing and maintaining a contacting or contactless measurement connection to a surface to be measured, the probe head being moveably linked to the basis by at least one joint, wherein the probe head comprises a stylus carrier (61, 161) and a hollow stylus (62, 62', 162) with a stylus tip, and • an optical monitoring system for measuring a displacement of the stylus tip with respect to the stylus carrier, the optical monitoring system comprising □ light emitting means (111, 112, 113, 114, 811, 812, 813, 814, 825, 825', 911) for generating a beam to be directed inside the stylus (62, 62', 162) towards the stylus tip, where at least parts of the beam are reflected as a returned beam propagating along an optical return path, and □ detector means (141, 142, 143, 144, 145, 541, 542, 543, 544, 841, 842, 843, 844, 845, 846, 941) for the returned beam being capable of generating an electrical output signal indicative of the displacement of the stylus tip, wherein • the light emitting means are built in such a way that the beam has at least two distinguishable light characteristics with a given characteristics distribution, characterized in that • the optical monitoring system further comprises an optically encoding component (100, 200, 300, 500, 600) positioned in the stylus carrier (61,161) in the optical return path and designed to transform the information of an impinging position (50, 50') of the returned beam upon the optical encoding component (100, 200, 300, 500, 600) into a change of the characteristics distribution of the returned beam, and • the detector means (141, 142, 143, 144, 145, 541, 542, 543, 544, 841, 842, 843, 844, 845, 846, 941) is sensitive for the at least two distinguishable light characteristics and built for generating the electrical output signal dependent on the changed characteristics distribution of the returned beam. • a basis, • a probe head for establishing and maintaining a contacting or contactless measurement connection to a surface to be measured, the probe head being moveably linked to the basis by at least one joint, wherein the probe head comprises a stylus carrier (61, 161) and a hollow stylus (62, 62', 162) with a stylus tip, and • an optical monitoring system for measuring a displacement of the stylus tip with respect to the stylus carrier, the optical monitoring system comprising □ light emitting means (111, 112, 113, 114, 811, 812, 813, 814, 825, 825', 911) for generating a beam to be directed inside the stylus (62, 62', 162) towards the stylus tip, where at least parts of the beam are reflected as a returned beam propagating along an optical return path, and □ detector means (141, 142, 143, 144, 145, 541, 542, 543, 544, 841, 842, 843, 844, 845, 846, 941) for the returned beam being capable of generating an electrical output signal indicative of the displacement of the stylus tip, wherein □ light emitting means (111, 112, 113, 114, 811, 812, 813, 814, 825, 825', 911) for generating a beam to be directed inside the stylus (62, 62', 162) towards the stylus tip, where at least parts of the beam are reflected as a returned beam propagating along an optical return path, and □ detector means (141, 142, 143, 144, 145, 541, 542, 543, 544, 841, 842, 843, 844, 845, 846, 941) for the returned beam being capable of generating an electrical output signal indicative of the displacement of the stylus tip, wherein • the light emitting means are built in such a way that the beam has at least two distinguishable light characteristics with a given characteristics distribution, characterized in that • the optical monitoring system further comprises an optically encoding component (100, 200, 300, 500, 600) positioned in the stylus carrier (61,161) in the optical return path and designed to transform the information of an impinging position (50, 50') of the returned beam upon the optical encoding component (100, 200, 300, 500, 600) into a change of the characteristics distribution of the returned beam, and • the detector means (141, 142, 143, 144, 145, 541, 542, 543, 544, 841, 842, 843, 844, 845, 846, 941) is sensitive for the at least two distinguishable light characteristics and built for generating the electrical output signal dependent on the changed characteristics distribution of the returned beam.