A sensor device for the examination of the surface of a cylindrical hollow enclosure - having at least two sensor units (10, 20), which are in each case set up for an optical confocal distance measurement, - wherein the at least two sensor units (10, 20) comprise at least one first sensor unit and at least one second sensor unit (10, 20), - wherein the at least two sensor units (10, 20) have in each case a light source and a light detector, or an optical waveguide and - wherein the at least two sensor units (10, 20) in each case have an elongated shape and contain an external optical system (13, 23), through which in each case a measuring direction (11, 21), in which light can be irradiated and be received, stands transverse to a longitudinal axis of the respective sensor unit (10, 20), - having a motion device, which is adapted to move the at least two sensor units (10, 20) in one direction of motion into and out of a cylindrical hollow enclosure to be examined, characterized in that - control means are provided for measuring protrusions on a surface of the cylindrical hollow enclosure and are adapted to control the first sensor unit for carrying out a first distance measurement, during which the measuring direction relative to the direction of motion is at an angle from 20° to 85°, and are adapted to control the second sensor unit for carrying out a second distance measurement, during which the measuring direction relative to the direction of motion is at an angle from 95° to 160°, - that the first sensor unit is formed in such a manner and linked with the movement mechanism that its measuring direction relative to the direction of motion is at an angle from 20° to 85°, - that the second sensor unit is formed and linked with the movement mechanism in such a manner that its measuring direction relative to the direction of motion is at an angle from 95° to 160°, - that at least one third sensor unit is provided, which is set for an optical confocal distance measurement, - that a measuring direction of said at least third sensor unit forms, relatively to the measuring directions (11, 21) of the first and second distance measurements, an angle within a plane at right angles to the direction of motion, which measures between 45° and 315°, - that the control means are adapted to determine variations in position of the first and second sensor unit (10, 20) in a plane at right angles to the direction of motion with the aid of distance measurement data of the at least third sensor unit. - having at least two sensor units (10, 20), which are in each case set up for an optical confocal distance measurement, - wherein the at least two sensor units (10, 20) comprise at least one first sensor unit and at least one second sensor unit (10, 20), - wherein the at least two sensor units (10, 20) have in each case a light source and a light detector, or an optical waveguide and - wherein the at least two sensor units (10, 20) in each case have an elongated shape and contain an external optical system (13, 23), through which in each case a measuring direction (11, 21), in which light can be irradiated and be received, stands transverse to a longitudinal axis of the respective sensor unit (10, 20), - having a motion device, which is adapted to move the at least two sensor units (10, 20) in one direction of motion into and out of a cylindrical hollow enclosure to be examined, characterized in that - control means are provided for measuring protrusions on a surface of the cylindrical hollow enclosure and are adapted to control the first sensor unit for carrying out a first distance measurement, during which the measuring direction relative to the direction of motion is at an angle from 20° to 85°, and are adapted to control the second sensor unit for carrying out a second distance measurement, during which the measuring direction relative to the direction of motion is at an angle from 95° to 160°, - that the first sensor unit is formed in such a manner and linked with the movement mechanism that its measuring direction relative to the direction of motion is at an angle from 20° to 85°, - that the second sensor unit is formed and linked with the movement mechanism in such a manner that its measuring direction relative to the direction of motion is at an angle from 95° to 160°, - that at least one third sensor unit is provided, which is set for an optical confocal distance measurement, - that a measuring direction of said at least third sensor unit forms, relatively to the measuring directions (11, 21) of the first and second distance measurements, an angle within a plane at right angles to the direction of motion, which measures between 45° and 315°, - that the control means are adapted to determine variations in position of the first and second sensor unit (10, 20) in a plane at right angles to the direction of motion with the aid of distance measurement data of the at least third sensor unit.