A method of laser machining a panel (101,401;601;701;801;901;1101;1201) using a movable optical head (422;610;1110;1310) that moves along a scanning axis, the method comprising: mounting the panel (101,401;601;701;801;901;1101;1201) on a part handling system (110;410;620;1120); generating at least one laser beam by means of at least one laser source (106;406;602;1306); and characterised by the following steps: directing the laser beam generated by a laser source mounted on a base, through a stationary beam delivery system, substantially parallel to the scanning axis and into at least one moving optical head (422;610;1110;1310) such that the optical head (422;610;1110;1310) located below the workpiece (101;401;601;701;801,901;1101; 1201) modifies the beam and directs at least one modified beam out of the optical head (422;610;1110;1310) substantially orthogonal to the scanning axis; moving the optical head (422;610;1110;1310) along the scanning axis and across the panel (101,401;601;701;801;901;1101;1201) such that the at least one modified beam scans the panel (101,401;601;701;801;901;1101;1201) and forms a scribe line (603a-603d;703;1103) in the panel (101,401;601;701;801;901;1101;1201); and tracking changes in a height of a process plane of the panel (101,401;601;701;801;901;1101;1201); and adjusting at least one scribing parameter in response to a detected change in the workpiece (101,401;601;701;801;901;1101;1201) or a scribe line (603a-603d;703;1103) on the workpiece (101,401;601;701;801;901;1101;1201), wherein adjusting at least one parameter includes at least changing a focus of the modified beam directed out of the optical head (422;610;1110;1310) in response to changes in the height of the process plane of the panel (101,401;601;701;801;901;1101;1201). mounting the panel (101,401;601;701;801;901;1101;1201) on a part handling system (110;410;620;1120); generating at least one laser beam by means of at least one laser source (106;406;602;1306); and characterised by the following steps: directing the laser beam generated by a laser source mounted on a base, through a stationary beam delivery system, substantially parallel to the scanning axis and into at least one moving optical head (422;610;1110;1310) such that the optical head (422;610;1110;1310) located below the workpiece (101;401;601;701;801,901;1101; 1201) modifies the beam and directs at least one modified beam out of the optical head (422;610;1110;1310) substantially orthogonal to the scanning axis; moving the optical head (422;610;1110;1310) along the scanning axis and across the panel (101,401;601;701;801;901;1101;1201) such that the at least one modified beam scans the panel (101,401;601;701;801;901;1101;1201) and forms a scribe line (603a-603d;703;1103) in the panel (101,401;601;701;801;901;1101;1201); and tracking changes in a height of a process plane of the panel (101,401;601;701;801;901;1101;1201); and adjusting at least one scribing parameter in response to a detected change in the workpiece (101,401;601;701;801;901;1101;1201) or a scribe line (603a-603d;703;1103) on the workpiece (101,401;601;701;801;901;1101;1201), wherein adjusting at least one parameter includes at least changing a focus of the modified beam directed out of the optical head (422;610;1110;1310) in response to changes in the height of the process plane of the panel (101,401;601;701;801;901;1101;1201). directing the laser beam generated by a laser source mounted on a base, through a stationary beam delivery system, substantially parallel to the scanning axis and into at least one moving optical head (422;610;1110;1310) such that the optical head (422;610;1110;1310) located below the workpiece (101;401;601;701;801,901;1101; 1201) modifies the beam and directs at least one modified beam out of the optical head (422;610;1110;1310) substantially orthogonal to the scanning axis; moving the optical head (422;610;1110;1310) along the scanning axis and across the panel (101,401;601;701;801;901;1101;1201) such that the at least one modified beam scans the panel (101,401;601;701;801;901;1101;1201) and forms a scribe line (603a-603d;703;1103) in the panel (101,401;601;701;801;901;1101;1201); and tracking changes in a height of a process plane of the panel (101,401;601;701;801;901;1101;1201); and adjusting at least one scribing parameter in response to a detected change in the workpiece (101,401;601;701;801;901;1101;1201) or a scribe line (603a-603d;703;1103) on the workpiece (101,401;601;701;801;901;1101;1201), wherein adjusting at least one parameter includes at least changing a focus of the modified beam directed out of the optical head (422;610;1110;1310) in response to changes in the height of the process plane of the panel (101,401;601;701;801;901;1101;1201).