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

Abstract

A laser machining device includes a first focus movement amount calculation section configured to calculate a focus movement amount based on comparison of a first measurement value obtained by averaging a plurality of measurement values measured by a returning light measurement unit within a first period and a second measurement value obtained by averaging a plurality of measurement values measured by the returning light measurement unit within a second period that is temporally later than the first period; and a focus position correction section configured to correct a focus position during laser machining based on the 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.