Laser processing optical system solution

Laser processing optical system solution
The determination of the laser processing optical system solution depends on the specific application scenario. Different scenarios lead to different solutions for the optical system. Specific analysis is required for specific applications. The optical system is shown in Figure 1:

The thinking path is: concrete process goals – laser characteristics – optical system scheme design – final goal realization. The following are several different application fields:
1. Precision micro-processing field (marking, etching, drilling, precise cutting, etc.) The common typical processes in the precision micro-processing field are micro-metric processing on materials such as metals, ceramics, and glass, such as logo marking for mobile phones, medical stents, micro holes for gas fuel injection nozzles, etc. The core requirement in the processing process is: first, it must meet extremely small focused light spots, extremely high energy density, and the smallest thermal influence zone, etc. For the above applications and requirements, the selection and design of laser light sources and other components are carried out.
a. Laser selection: The preferred ultraviolet/green solid laser (nanosecond) or ultrafast laser (picosecond, femtosecond) is mainly due to two reasons. One is that the wavelength is proportional to the focused light spot, and generally a short wavelength is chosen. The second is that the picosecond/femtosecond pulses have the “cold processing” characteristic, and the energy is completed processing before thermal diffusion, achieving cold processing. Generally, a laser light source with spatial light output is selected, with a beam quality factor M2 generally less than 1.1, having superior beam quality.
b. Beam expanding system and collimating system usually use variable magnification beam expanding lenses (2X – 5X), trying to increase the beam diameter as much as possible. The beam diameter is inversely proportional to the focused light spot, and a Galilean beam expanding architecture is generally used.
c. Focusing system usually uses high-performance F-Theta lenses (for scanning) or telecentric focusing lenses. The focal length is proportional to the focused light spot, and generally short focal field lenses (such as f = 50mm, 100mm) are used. As shown in Figure 1: Generally, the field lens uses a multi-element lens group (the number of lenses ≥ 3), which can achieve large field of view, large aperture, and low aberration indicators. The optical lenses here all need to consider the laser’s damage threshold.
d. Coaxial monitoring optical system: In the optical system, a coaxial vision (CMOS) system is usually integrated for precise positioning and real-time monitoring of the processing process.
2. Macro-material processing The typical application scenarios of macro-material processing include cutting of automotive sheet materials, welding of ship body steel plates, and welding of battery housing shells. These processes require high power, high penetration capability, high efficiency, and processing stability.
3. Laser additive manufacturing (3D printing) and cladding laser additive manufacturing (3D printing) and cladding applications typically involve the following typical processes: aerospace complex metal printing, engine blade repair, etc.
The selection of core components is as follows:
a. Laser selection: Generally, high-power fiber lasers are chosen, with a power typically exceeding 500W.
b. Beam shaping: This optical system needs to output a flat-top light, so beam shaping is the core technology, and it can be achieved using diffractive optical elements.
c. Focusing system: Mirrors and dynamic focusing are the basic requirements in the 3D printing field. At the same time, the scanning lens needs to use an object-side telecentric design to ensure consistency in edge and center processing.