Laser Cylinder Surface Structuring With Bessel Beam Resolution
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Solution Overview
Problem
Current laser structuring methods for cylinder surfaces are limited by resolution, as they cannot achieve spot diameters smaller than 2 micrometers, which is insufficient for nanostructures and applications in printed electronics, and the processing speed is not optimized.
Innovation Solution
The method involves using a Bessel beam focused and repositioned relative to the optical axis of the optics, with the aid of beam shapers and modulators, to achieve higher resolution and faster processing by allowing precise control of individual points on the cylinder surface during rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional Gaussian laser beams are used for surface structuring, then the processing is simpler, but the spot diameter cannot be smaller than approximately 2 micrometers, limiting resolution
Solution Approach 1:
The patent transforms the conventional Gaussian beam intensity distribution into a Bessel beam intensity distribution by changing the optical parameters and using axicons. This parameter change enables the laser beam to achieve a much smaller central spot diameter (below 2 micrometers) while maintaining a longer depth of field, thereby improving manufacturing precision without proportionally increasing device complexity
Solution Approach 2:
The patent segments the laser beam into multiple focal points along the propagation direction using axicons, creating a Bessel beam with a long non-diffracting range. This segmentation of the focal energy along the z-axis allows the central spot to remain small over an extended depth, effectively improving resolution while managing the complexity through controlled beam transformation
2Manufacturing precision
If the laser beam is focused to a small spot diameter, then resolution improves, but the processing speed decreases due to limited coverage area
Solution Approach 1:
The patent introduces the longitudinal dimension (z-axis) into the focusing problem by creating a Bessel beam with an extended depth of field. Instead of concentrating energy in a single tight focal plane that limits scanning speed, the Bessel beam distributes energy along the propagation direction, allowing the transverse spot size to remain small while the effective processing depth increases, thus improving both resolution and processing speed
Solution Approach 2:
The Bessel beam's extended depth of field enables continuous useful action over a longer processing path. As the laser scans across the cylinder surface, the Bessel beam maintains its small spot diameter and high intensity over an extended z-range, allowing uninterrupted high-resolution structuring without frequent refocusing, thereby improving processing speed while maintaining resolution
3Device complexity
If mechanical or lithographic processes are used for surface structuring, then the equipment is simpler, but multiple process steps including masking and chemical treatments are required
Solution Approach 1:
The patent replaces mechanical masking and chemical etching processes with a purely optical field-based approach. By using Bessel beam focusing, the laser directly ablates or modifies the material with sub-2-micrometer precision without requiring physical masks or chemical treatments. This substitution of mechanical/chemical systems with an optical field system reduces the number of process steps while achieving superior resolution
Solution Approach 2:
The patent changes the fundamental parameter of energy concentration by using Bessel beam optics instead of conventional Gaussian focusing. This parameter change in the intensity distribution enables direct material structuring at high resolution through controlled laser ablation, eliminating the need for mask alignment and chemical processing steps that characterize traditional methods
4Area of stationary object
If the optical axis moves continuously along the cylinder, then the processing coverage is improved, but the ability to address individual points precisely is reduced
Solution Approach 1:
The patent introduces dynamic control of the laser beam position through acousto-optical or electro-optical modulators that can rapidly deflect the beam in the transverse direction. This dynamic adjustment allows the system to move beyond simple continuous optical axis scanning and precisely target individual points or patterns on the rotating cylinder, maintaining point addressing accuracy while achieving comprehensive area coverage through coordinated rotation and beam deflection
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables higher resolution and accelerated processing, achieving a high ablation effect in a small central area with improved energy input and spatial control, allowing for the creation of fine structures in the micrometer and even nanometer range.
Implementation Method 1
Ablating material with laser pulses eliminates many complex process steps
Implementation Method 2
This allows for a high ablation effect to be achieved, preferably in a small central region of the beam
Implementation Method 3
Focusing with current processes is limited to spot diameters of approximately 2 micrometers (μm)
Implementation Method 4
A Bessel beam, in particular, allows for a particularly high energy input with a small diameter
Implementation Method 5
the optical axis of the optical system is or can be moved in particular along a helical line over the cylinder surface
Data Source
Figure 1~3
Figure 4~5
AI summary
The invention relates to a method and a device (10) for structuring the surface (12) of a cylinder (11) using at least one laser beam (13), such as, in particular, a printing cylinder and/or embossing cylinder, preferably by laser ablation. The laser beam (13) is positioned on the cylinder surface (12) by means of an optic (15). The cylinder (11) is rotated about its longitudinal axis (26), wherein the optical axis (17) of the optic (15) is moved relative to the cylinder (11) along the longitudinal axis (25), preferably continuously or at least substantially continuously, such that the optical axis (17) of the optic (15) is movable, or is moved, in particular along a helical path across the cylinder surface (12). The laser beam (13) is focused and/or shaped as a Bessel beam and/or repositioned relative to the optical axis of the optic (17).