Laser cutting machine

A laser cutting machine for irradiating a moveable laser beam onto a workpiece to cut the workpiece, comprising:

• a laser oscillator for providing said laser beam from a beam outlet;
• a first rail structure comprising a pair of parallel rails disposed to define a first axis;
• an arm provided movably in the direction of said first axis on said first rail structure;
• a second rail structure disposed on said arm to define a second axis, said second axis being perpendicular to said first axis;
• a cutting head provided movably on said second rail structure in the direction of said second axis;
• a first bend mirror which is a circular-polarizing mirror disposed on said first axis for receiving said laser beam output by said laser oscillator;
• a second bend mirror disposed on said first axis for receiving said laser beam reflected by said first mirror;
• a third bend mirror and a fourth bend mirror provided on said arm;
• a fifth bend mirror provided on said cutting head;
• said first, second, third, fourth and fifth bend mirrors defining a laser beam path, and said cutting head being moveable within a moveable range to change a beam axis distance;
• a collimation optical means disposed so that said laser beam is focused at a position approximately in the middle of said movable range of said cutting head;
• and
• a concave optical means installed between said beam outlet of said laser oscillator and said collimation optical means,
• wherein said second to fifth bend mirrors are disposed to counterbalance phase shift amounts specific to said second to fifth bend mirrors.