Laser Iridescent Surface Structuring With Overlapped Optical Fields
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Solution Overview
Problem
Current laser treatment methods for achieving iridescence on large stainless steel sheets face challenges such as non-homogeneous treatment, visibility of junction zones between optical fields, and excessive directionality of the iridescence effect, due to limitations in focusing systems and synchronization issues at high scanning speeds.
Innovation Solution
A method involving the use of ultra-short pulse lasers with overlapping optical fields and varying polarization angles to create a random or periodic pattern of junctions, ensuring uniform energy distribution and minimizing the visibility of treatment boundaries, while maintaining high productivity for industrial-scale applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple optical fields are used to treat large surfaces, then productivity and coverage area are improved, but junction zones between fields become visible and treatment homogeneity deteriorates
Solution Approach 1:
The treatment of large surfaces is divided into multiple optical fields that are processed sequentially. Each optical field is treated independently by the laser device, allowing the large surface area to be covered while maintaining control over each segment's treatment quality. The junction zones between these segmented fields are managed through careful overlap design to ensure homogeneity across the entire treated surface.
2Productivity
If high scanning speeds are used to maintain productivity, then processing efficiency is improved, but synchronization issues arise and treatment precision deteriorates
Solution Approach 1:
The laser device operates with periodic pulsed radiation rather than continuous scanning. This periodic action allows for precise timing and synchronization control, where each pulse is delivered at predetermined intervals. The pulse duration is kept short (less than one nanosecond) to ensure that even at high scanning speeds, the energy delivery remains precisely controlled and synchronized with the scanning motion, preventing treatment defects.
3Manufacturing precision
If pulsed laser radiation is used to create iridescence, then surface structure modification is achieved, but energy control becomes critical to avoid ablation
Solution Approach 1:
The laser device operates by precisely controlling key parameters including pulse duration (less than one nanosecond), pulse energy, and scanning speed. By adjusting these parameters within specific ranges, the treatment achieves the desired surface modification for iridescence without exceeding the energy threshold that would cause ablation. The pulse duration is specifically kept short to allow precise energy delivery and rapid cooling between pulses, maintaining surface integrity while creating the periodic structure.
4Reliability
If short pulse duration is used to prevent ablation, then surface integrity is maintained, but energy density increases requiring precise control
Solution Approach 1:
The system incorporates control mechanisms that monitor and adjust laser parameters in real-time to ensure uniform energy distribution across the surface. The feedback control maintains consistent pulse energy and timing, compensating for variations in scanning speed or positioning. This ensures that the high energy density of short pulses is distributed uniformly, preventing localized ablation while maintaining surface integrity throughout the treated area.
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
The method achieves a visually uniform and intense iridescence effect across large surfaces, reducing the visibility of junction zones and addressing directionality issues, thereby enhancing the homogeneity and aesthetic appeal of treated surfaces.
Implementation Method 1
irradiating the surface of a material with pulsed laser radiation of short pulse duration (less than one nanosecond)
Implementation Method 2
If the energy of the incident beam is sufficiently high, this irradiation induces the modification of the structure and/or the reorganization of the surface of the material which will adopt a periodic structure
Implementation Method 3
this periodic surface organization allows for an induced phenomenon, well known to practitioners of laser surface treatments, which is the diffraction of light through the creation of an optical grating when the treated sample is placed under a light source
Implementation Method 4
Between performing the scan along two successive lines in said direction of relative movement of the part and the scanner(s), the polarization of the laser beam is modified so as to create wavelets of different orientations on said two successive lines
Data Source
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AI summary
The invention relates to a method for creating an iridescent effect on the surface of a part (1). In said method, laser beams (9) having a pulse duration of less than a nanosecond are sent onto said surface in the juxtaposed optical fields of the focusing systems (14) of at least two fixed devices, or in the field of at least one mobile device, the one or more devices each comprising a laser source (8), a scanner (13) and said focusing system (14) for applying a structure in the form of wavelets to said surface over the width of said pulse, and the at least one scanner (13) scans the surface by means of said laser beams (9) along a series of lines (5, 6; 16, 17, 18, 16', 17', 18') that follow each other in a relative direction of travel (7) of the part (1) and of the at least one scanner (13) and a series of lines which lie in the continuation of each other in a direction perpendicular to said relative direction of travel (7) and each of which belongs to the optical field of the one or more devices, each line (5, 6; 16, 17, 18, 16', 17', 18') having a width that is equal to the diameter of said pulse. The optical fields overlap in an overlapping area having a width ranging from twice the diameter of the pulse of the laser beam (9) to 2 cm, such that two lines lying in the continuation of each other overlap at a junction (2), and between two series of lines (5, 6; 16, 17, 18, 16', 17', 18') following each other in a relative direction of travel (7) of the part (1) and of the at least one scanner (13), said junction areas (2) are arranged randomly or periodically organized in a random pattern inside said overlapping area of the optical fields.