Variable Curvature Mirror for Laser Beam Expansion
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Solution Overview
Problem
The existing laser processing devices with spherical mirrors in the reflective beam expander mechanism face complications in optical path configuration and inability to satisfactorily inhibit astigmatism, leading to reduced processing quality due to beam divergence and anisotropy.
Innovation Solution
Incorporating a variable curvature spherical mirror and a mirror with different curvatures in two orthogonal axes in the reflective beam expander mechanism, allowing for collimation and magnification of laser light without restricting the incident angle, thus simplifying the optical path and preventing astigmatism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a spherical mirror is used in the reflective beam expander mechanism, then the optical system can be simplified, but astigmatism occurs when the incident angle is not acute, reducing processing quality
Solution Approach 1:
The patent applies asymmetry by using a toroidal mirror instead of a spherical mirror. The toroidal mirror has different curvatures in two orthogonal directions (different radii of curvature in meridional and sagittal directions), which allows it to correct astigmatism inherently by matching the asymmetric wavefront errors. This asymmetric geometry enables the mirror to focus light differently in different planes, thereby eliminating the astigmatism problem that plagues spherical mirrors when used at non-acute incident angles.
Solution Approach 2:
The patent changes the geometric parameters of the mirror from a spherical shape (equal curvature in all directions) to a toroidal shape (different curvatures in different directions). By adjusting the radii of curvature in the meridional and sagittal directions independently, the system can optimize the mirror's focusing properties for specific incident angles, thereby maintaining high processing quality without requiring acute angle incidence and simplifying the overall optical path.
2Manufacturing precision
If a reflection mirror is added to restrict incident angles with respect to spherical mirrors, then astigmatism can be inhibited, but the optical path becomes complicated and processing stability decreases
Solution Approach 1:
The patent extracts and removes the need for additional incident angle restriction mirrors by directly using a toroidal mirror in the reflective beam expander mechanism. The toroidal mirror's inherent asymmetric geometry allows it to handle non-acute incident angles without generating astigmatism, thereby eliminating the need for separate angle-restricting optical elements and simplifying the overall optical path configuration.
Solution Approach 2:
The toroidal mirror acts as an intermediary optical element that mediates between the laser source and the processing target. Its unique geometry allows it to correct astigmatism while accommodating various incident angles, serving as a single element that performs the function previously requiring multiple mirrors and angle-restricting components.
3Manufacturing precision
If multiple optical elements are added to the optical path, then astigmatism can be controlled, but thermal lens effects increase and processing stability decreases
Solution Approach 1:
The patent merges the functions of multiple optical elements into a single toroidal mirror. Instead of using separate spherical mirrors with additional angle-restricting mirrors, the toroidal mirror combines beam expansion, collimation, and astigmatism correction functions in one element. This reduction in the number of optical elements minimizes cumulative thermal lens effects and improves processing stability.
Solution Approach 2:
The toroidal mirror serves as an intermediary that reduces the total number of optical interfaces and elements in the path. By consolidating optical functions into this single element with optimized geometry, the system reduces thermal accumulation and associated instability while maintaining high processing quality.
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 configuration effectively restricts beam divergence and maintains a desired beam diameter without aberration, enhancing processing stability and quality by reducing the complexity of the optical system and eliminating the need for additional reflection mirrors.
Implementation Method 1
the reflective beam expander mechanism includes a spherical mirror and a mirror having different curvatures in two orthogonal axes
Data Source
AI summary
A laser processing device including: a laser oscillator; a processing table; a transmission optical system for transmitting laser light emitted from the laser oscillator to the processing table; a processing head for condensing and radiating the laser light transmitted via the transmission optical system to an object to be processed; a moving mechanism for changing a relative position between the object to be processed and the laser light to be radiated to the object to be processed; and a variable curvature spherical mirror. The transmission optical system includes a reflective beam expander mechanism for collimating and magnifying the laser light from the laser oscillator. The reflective beam expander mechanism includes a spherical mirror and a concave mirror having different curvatures in two orthogonal axes.