A scanner assembly for measuring wear in a refractory lining, comprising: a first proximal end, a first distal end, and a longitudinal axis extending from the first proximal end to the first distal end; a mounting arm having a second proximal end and a second distal end and located at the first distal end of the scanner assembly; a turret having a third proximal end and a third distal end, wherein the third proximal end of the turret is rotatably mounted on the second distal end of the mounting arm, in that the turret can rotate relative to the mounting arm about the longitudinal axis; and an emitter/sensor mounted in the turret; wherein emitter/sensor comprises an optical center; wherein the emitter/sensor contains a laser, optics, a photodetector and receiver electronics; wherein the optical center of the emitter/sensor is located on the longitudinal axis; wherein a field of view of the emitter/sensor is contained in a plane also containing scanner assembly longitudinal axis; wherein the field of view comprises a distal limit extending from the distal end of the turret, and comprises a proximal limit disposed opposite to the distal limit; characterized in that - the field of view of the emitter/sensor is described, in the longitudinal direction, by an obtuse angle containing, in all rotation positions of the turret around scanner assembly longitudinal axis, the extension of the longitudinal axis from the distal end of the scanner assembly, and containing a line extending from the emitter/sensor in a plane orthogonal to the longitudinal axis, - the emitter/sensor is mounted in a fixed position in the turret, the emitter/sensor being configured to fire rapid pulses of laser light at a target surface and being configured to measure the amount of time it takes for each pulse to return from the target surface to the scanner assembly through the field of view. a mounting arm having a second proximal end and a second distal end and located at the first distal end of the scanner assembly; a turret having a third proximal end and a third distal end, wherein the third proximal end of the turret is rotatably mounted on the second distal end of the mounting arm, in that the turret can rotate relative to the mounting arm about the longitudinal axis; and an emitter/sensor mounted in the turret; wherein emitter/sensor comprises an optical center; wherein the emitter/sensor contains a laser, optics, a photodetector and receiver electronics; wherein the optical center of the emitter/sensor is located on the longitudinal axis; wherein a field of view of the emitter/sensor is contained in a plane also containing scanner assembly longitudinal axis; wherein the field of view comprises a distal limit extending from the distal end of the turret, and comprises a proximal limit disposed opposite to the distal limit; characterized in that - the field of view of the emitter/sensor is described, in the longitudinal direction, by an obtuse angle containing, in all rotation positions of the turret around scanner assembly longitudinal axis, the extension of the longitudinal axis from the distal end of the scanner assembly, and containing a line extending from the emitter/sensor in a plane orthogonal to the longitudinal axis, - the emitter/sensor is mounted in a fixed position in the turret, the emitter/sensor being configured to fire rapid pulses of laser light at a target surface and being configured to measure the amount of time it takes for each pulse to return from the target surface to the scanner assembly through the field of view. - the field of view of the emitter/sensor is described, in the longitudinal direction, by an obtuse angle containing, in all rotation positions of the turret around scanner assembly longitudinal axis, the extension of the longitudinal axis from the distal end of the scanner assembly, and containing a line extending from the emitter/sensor in a plane orthogonal to the longitudinal axis, - the emitter/sensor is mounted in a fixed position in the turret, the emitter/sensor being configured to fire rapid pulses of laser light at a target surface and being configured to measure the amount of time it takes for each pulse to return from the target surface to the scanner assembly through the field of view.