Laser machining device for adjusting focus shift based on contamination level of optical system during laser machining

A laser machining device configured to laser machine a workpiece while correcting a focus shift due to contamination of an optical system, the laser machining device comprising:

• a laser oscillator;
• an external optical system being external to the laser oscillator and configured to guide laser light from the laser oscillator and focus the laser light on the surface of a workpiece;
• a returning light measurement unit that measures an energy amount of returning light reflected by the workpiece and returning to the laser machining device;
• and
• a focus shift adjustment unit that adjusts, based on the energy amount of the returning light of the laser light having an output as high as that used for laser cutting during laser cutting, a focus shift due to contamination of the external optical system, wherein
• the focus shift adjustment unit:
• issues, with respect to the laser oscillator, a command to emit laser light at a predetermined output or a command to not emit laser light;
• calculates a focus movement amount based on comparison of a first measurement value obtained by averaging peak values measured by the returning light measurement unit when changing from the command not to emit laser light to the command to emit laser light within a first period and a second measurement value obtained by averaging peak values measured by the returning light measurement unit when changing from the command not to emit laser light to the command to emit laser light within a second period that is temporally later than the first period;
• and
• corrects a focus position during laser cutting based on the calculated focus movement amount, and
• the first period is a period shortly after initiation of laser emission when the external optical system is not warmed up or is a period after correcting the focus position, and the second period is a period after passage of a certain time duration when the external optical system is warmed up.

A laser machining device configured to laser machine a workpiece while correcting a focus shift due to contamination of an optical system, the laser machining device comprising:

• a laser oscillator;
• an external optical system being external to the laser oscillator and configured to guide laser light from the laser oscillator and focus the laser light on the surface of a workpiece;
• a returning light measurement unit that measures an energy amount of returning light reflected by the workpiece and returning to the laser machining device;
• and
• a focus shift adjustment unit that adjusts, based on the energy amount of the returning light of the laser light having an output as high as that used for laser cutting during laser cutting, a focus shift due to contamination of the external optical system,
• wherein
• the focus shift adjustment unit:
• calculates a change amount per unit time of the energy amount of the returning light measured by the returning light measurement unit;
• calculates a focus movement amount based on comparison of a first measurement value obtained by averaging peak values measured by the returning light measurement unit when the calculated change amount per unit time within a first period is greater than or equal to a certain value and a second measurement value obtained by averaging peak values measured by the returning light measurement unit when the calculated change amount per unit time within a second period that is temporally later than the first period is equal to or greater than a certain value;
• and
• corrects a focus position during laser cutting based on the calculated focus movement amount, and
• the first period is a period shortly after initiation of laser emission when the external optical system is not warmed up or is a period after correcting the focus position, and the second period is a period after passage of a certain time duration when the external optical system is warmed up.

A laser machining device configured to laser machine a workpiece while correcting a focus shift due to contamination of an optical system, the laser machining device comprising:

• a laser oscillator;
• an external optical system being external to the laser oscillator and configured to guide laser light from the laser oscillator and focus the laser light on the surface of a workpiece;
• a returning light measurement unit that measures an energy amount of returning light reflected by the workpiece and returning to the laser machining device;
• and
• a focus shift adjustment unit that adjusts, based on the energy amount of the returning light of the laser light having an output as high as that used for hole formation machining during hole formation machining, a focus shift due to contamination of the external optical system, wherein
• the focus shift adjustment unit:
• calculates a first focus movement amount based on a comparison of a first measurement value measured by the returning light measurement unit at a time of a first hole formation machining and a second measurement value measured by the returning light measurement unit at a time of a second hole formation machining that is temporally later than the time of the first hole formation machining;
• and
• corrects a focus position during hole formation machining based on the calculated focus movement amount, and
• the time of the first hole formation machining is a point in time shortly after initiation of laser emission when the external optical system is not warmed up or is a point in time after correcting the focus position, and the time of the second hole formation machining is a point in time after passage of a certain time duration when the external optical system is warmed up.