Surface sensing device with optical monitoring system

A monitoring method for a probe head of a surface sensing device, the probe head comprising a stylus carrier and a hollow stylus with a stylus tip, the monitoring method being designed for measuring a displacement of the stylus tip with respect to the stylus carrier, the monitoring method comprising:

• directing a beam having at least two distinguishable light characteristics with a given characteristics distribution inside the stylus towards the stylus tip, where at least parts of the beam are reflected as a returned beam propagating along an optical return path,
• transforming the information dependent on an impinging position of the returned beam upon an optically encoding component positioned in the stylus carrier in the optical return path into a change of the characteristics distribution of the returned beam;
• detecting the at least two distinguishable light characteristics of the returned beam, and
• determining the displacement of the stylus tip with respect to the stylus carrier dependent on the changed characteristics distribution of the returned beam.

A 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 and a hollow stylus 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 including:
• light emitting means for generating a beam to be directed inside the stylus 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 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;
• the optical monitoring system further comprises an optically encoding component positioned in the stylus carrier in the optical return path and designed to modify the returned beam into a change of the characteristics distribution of the returned beam, wherein the modification varies dependent on the impinging position of the returned beam upon the optical encoding component;
• the detector means 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.