Method for detecting the operating condition of an optical element arranged along a propagation path of a laser beam of a machine for processing a material, system for carrying out said method and laser processing machine provided with said system

A system for detecting an operating condition of at least one optical element arranged along an optical propagation path of a power laser beam in a processing head of a machine for laser processing of a material, in particular for laser cutting, drilling or welding said material,

• said power laser beam having a predetermined transverse power distribution at a predetermined operative wavelength, and
• said optical propagation path of the power laser beam within said processing head comprising a plurality of cascaded optical elements,
• the system comprising:
• an electronic processing and control means;
• a first sensor arranged upstream of said at least one optical element to detect a first optical radiation which propagates coaxially to the optical propagation path in a direction opposite to the direction of propagation of the power laser beam, having a wavelength corresponding to the wavelength of the power laser beam, wherein said electronic processing and control means acquires a first signal or data, LSC, indicative of the first optical radiation;
• a second sensor arranged upstream of said at least one optical element to detect a second optical radiation which propagates coaxially to the optical propagation path in an opposite direction to the propagation direction of the power laser beam, having a wavelength in near infrared range, wherein said electronic processing and control means acquires a second signal or data, TSC, indicative of the second optical radiation;
• a third sensor associated with said at least one optical element to detect a proximity optical radiation emitted by said at least one optical element at a wavelength comprised in infrared range in a first volume region in proximity to an upstream surface of the at least one optical element with respect to said optical propagation path, wherein said electronic processing and control means acquires a third signal or data, IRV, indicative of the proximity optical radiation;
• a fourth sensor associated with said at least one optical element to detect time-of-flight of an acoustic wave through the volume of said at least one optical element within which said acoustic wave is emitted, wherein the electronic processing and control means acquires a fourth signal or data, PS, which is a function of the time-of-flight;
• and
• wherein said electronic processing and control means is further arranged to:
• calculate a normalized signal or data of proximity optical radiation, IRV_norm, for said at least one optical element, as a function of the third signal or data, IRV, indicative of the proximity optical radiation emitted by said at least one optical element, of the second signal or data, TSC, indicative of the second optical radiation, and of the first signal or data, LSC, indicative of the first optical radiation;
• calculate a signal or data of real proximity optical radiation, IRV_real, for said at least one optical element, as a function of the normalized signal or data of proximity optical radiation, IRV_norm, and of the fourth signal or data PS that is a function of the time-of-flight of the acoustic wave launched through the volume of said at least one optical element;
• and
• calculate a signal or data indicative of the operating condition, SS, of said at least one optical element, as a function of the signal or data of real proximity optical radiation, IRV_real, of the second signal or data, TSC, indicative of the second optical radiation, and of the first signal or data, LSC, indicative of the first optical radiation.