Sensor apparatus for detecting an object comprising - a sensor head having a plurality of receiving spaces for optical sensor devices - a plurality of optical devices, each being associated to one receiving space and - a driving mechanism for providing a relative movement of the object relative to the sensor head in an advance direction during a detecting operation, - the receiving spaces are arranged in a plurality of rows and columns, such that an array of receiving spaces is formed, and - the array of receiving spaces is tilted with regard to the advance direction such that the rows extend in a transverse direction relative to the advance direction and the receiving spaces of a successive row of the rectangular pattern are offset with regard to the receiving spaces of a preceding row of the rectangular pattern in a direction perpendicular to the advance direction, - the array of the receiving spaces has a rectangular pattern, - the sensor head comprises a receiving plate having a plurality of receiving holes formed as through-holes therein, the receiving holes forming the receiving spaces for the optical sensor devices, - the optical sensor devices each include a ferrule which is inserted into a receiving hole of the receiving plate, - the optical sensor devices each comprise a fibre, which is arranged in the ferrule and an optical sensor connected to the fibre, - the receiving holes are formed to tightly and removably hold the individual ferrules therein, and - the sensor head is rotatable about an axis perpendicular to the advance direction such that the amount of offset of the receiving spaces is adjustable - the rectangular pattern of rows and columns is tilted to a degree in which at least a part of the receiving spaces of at least one row of the rectangular pattern is aligned with at least a part of the receiving spaces of at least one preceding row in the advance direction characterized in that a lighting element, in particular a light emitting diode, is arranged within the ferrule which is at least partly transparent. - a sensor head having a plurality of receiving spaces for optical sensor devices - a plurality of optical devices, each being associated to one receiving space and - a driving mechanism for providing a relative movement of the object relative to the sensor head in an advance direction during a detecting operation, - the receiving spaces are arranged in a plurality of rows and columns, such that an array of receiving spaces is formed, and - the array of receiving spaces is tilted with regard to the advance direction such that the rows extend in a transverse direction relative to the advance direction and the receiving spaces of a successive row of the rectangular pattern are offset with regard to the receiving spaces of a preceding row of the rectangular pattern in a direction perpendicular to the advance direction, - the array of the receiving spaces has a rectangular pattern, - the sensor head comprises a receiving plate having a plurality of receiving holes formed as through-holes therein, the receiving holes forming the receiving spaces for the optical sensor devices, - the optical sensor devices each include a ferrule which is inserted into a receiving hole of the receiving plate, - the optical sensor devices each comprise a fibre, which is arranged in the ferrule and an optical sensor connected to the fibre, - the receiving holes are formed to tightly and removably hold the individual ferrules therein, and - the sensor head is rotatable about an axis perpendicular to the advance direction such that the amount of offset of the receiving spaces is adjustable - the rectangular pattern of rows and columns is tilted to a degree in which at least a part of the receiving spaces of at least one row of the rectangular pattern is aligned with at least a part of the receiving spaces of at least one preceding row in the advance direction