Keywords: laser engraving, depth control, beam shaping

Laser engraving vaporizes wood instantly by focusing the light spot, and its depth depends on power density, pulse width, and beam quality, requiring precise processing through multi parameter collaborative control.

1. Power density and material interaction model

The laser ablation threshold of wood is closely related to density and moisture content:

Hardwood (such as oak): The ablation threshold is about 5J/cm 2, and a power density of>10 ^ 6 W/cm 2 is required to achieve rapid gasification;

Cork (such as birch): The ablation threshold is only 2J/cm 2, and it is prone to carbonization due to high power, requiring multiple scans with low power (10-20W).

2. Core technology of deep control

Layered carving algorithm:

Split the target depth into N layers (usually N=5-10), and after engraving each layer, measure the actual depth using a laser confocal microscope. Dynamically adjust the power of the next layer (Δ P=k ·Δ d, where k is the proportionality coefficient) to achieve closed-loop control.

Pulse width optimization:

Nanosecond laser (10-9 seconds) is suitable for shallow carving (<0.5mm), while picosecond laser (10-12 seconds) can achieve "cold processing", reduce the heat affected zone, and is suitable for micro carving (<0.01mm). For example, carving 0.05mm wide "Preface to Lanting" text on 0.3mm thick boxwood chips, with picosecond laser edge burrs<1 μ m.

3. Beam shaping technology

Flat top beam generation:

The energy of traditional Gaussian beams follows a bell shaped distribution, leading to carbonization of the carved edges. By using diffractive optical elements (DOE) to shape the beam into a flat top distribution, the energy uniformity is increased from 70% to 95%, and the edge clarity is significantly improved.

Dynamic Focus System:

For curved surface carving (such as the inner wall of a wooden bowl), liquid lenses or acousto-optic deflectors are used to adjust the focal length in real time, ensuring that the light spot is always focused on the material surface with a depth error of<0.02mm.

4. Industry application cases

A cultural and creative enterprise used the "flat top beam+dynamic focusing" technology to carve a 3D map on a 20cm diameter wooden ball with a surface roughness Ra<1.6 μ m, winning the 2023 German Red Dot Design Award.

Future trend: The combination of ultrafast laser (attosecond level) and artificial intelligence can recognize wood texture in real time and automatically adjust the carving path, achieving intelligent processing of "carving according to wood".