A measurement module for a laser processing apparatus comprising:
- a connection port for optically coupling the measurement module to a distance detection device and a coupling port for optically coupling the measurement module to a laser processing module of the laser processing apparatus;
- a first optical path and a second optical path for laser light received and outputted through the connection port, wherein the first optical path is defined from the connection port to a reference optical reflector of the measurement module, wherein the reference optical reflector reflects said laser light back to the connection port, and wherein the second optical path is defined from the connection port to the coupling port and back to the connection port;
- wherein the measurement module further comprises a first optical path length regulator system for adjusting a first optical path length of the first optical path and a second optical path length regulator system for adjusting a second optical path length of the second optical path;
- wherein the first optical path length regulator system is coupled with the second optical path length regulator system, such that a first optical path length variation of the first optical path length is coupled with a second optical path length variation of the second optical path length;
- wherein the first optical path length regulator system comprises a first group of tilted reflection elements for multiply reflecting the laser light along the first optical path at reflecting surfaces thereof, wherein the reflective surfaces of the reflection elements of the first group face each other and are angled with respect to each other at least pairwise, such that a beam of said laser light incident upon the first group is reflected several times between the reflective surfaces thereof, wherein an extension of the first optical path between the tilted reflection elements of the first group is adjustable by setting a relative position between said reflection elements of the first group;
- wherein the first optical path length regulator system is configured for implementing said first optical path length variation by setting the relative position between said reflection elements of the first group;
- and
- wherein the second optical path length regulator system comprises a second group of tilted reflection elements for multiply reflecting the laser light along the second optical path at reflecting surfaces thereof, wherein the reflective surfaces of the reflection elements of the second group face each other and are angled with respect to each other at least pairwise, such that a beam of said laser light incident upon the second group is reflected several times between the reflective surfaces thereof, wherein an extension of the second optical path between the tilted reflection elements of the second group is adjustable by setting a relative position between said reflection elements of the second group;
- wherein the second optical path length regulator system is configured for implementing said second optical path length variation by setting the relative position between said reflection elements of the second group.