Reflective Laser Focusing Optics for Chromatic Aberration Control
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Solution Overview
Problem
Laser processing techniques face challenges in achieving high precision and productivity due to chromatic aberration, which causes the focal point of a laser beam to shift with different wavelengths, leading to processing quality deterioration and defects.
Innovation Solution
A laser processing apparatus is designed with a light converging unit that includes a through-hole optical element, a composite optical element with a central focusing hole, and a focusing lens, along with a position adjustment unit using galvano mirrors, to prevent focal point shifts due to chromatic aberration and correct distortion aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a transmissive lens is used to focus the laser beam, then the beam can be converged to a focal point, but chromatic aberration occurs causing the focal point position to change according to wavelength
Solution Approach 1:
The patent replaces the transmissive lens with a reflective optical system consisting of a concave mirror and a convex mirror. This substitution eliminates chromatic aberration because reflection does not depend on wavelength, unlike refraction through lenses. The concave mirror focuses the laser beam while the convex mirror corrects distortion aberration, achieving both focal point accuracy and wavelength independence.
Solution Approach 2:
The patent changes the optical path parameters by using curved reflective surfaces with specific curvatures. The concave mirror has a first curvature radius and the convex mirror has a second curvature radius, which are optimized to achieve precise focusing while correcting aberrations. This parameter optimization allows the system to maintain focal point stability across different wavelengths.
2Power
If pulse type lasers with shorter pulse duration are used to achieve high instantaneous output, then processing power increases, but spectral bandwidth broadens causing chromatic aberration to worsen
Solution Approach 1:
By replacing the transmissive lens with a reflective optical system, the patent eliminates chromatic aberration that would otherwise be exacerbated by the broadened spectral bandwidth of short-pulse lasers. This allows the use of high-power pulse lasers without suffering from wavelength-dependent focal point shifts, thereby maintaining processing quality while achieving high instantaneous output.
3Ease of operation
If lenses and mirrors are used for refracting and reflecting laser beams, then beam manipulation is achieved, but distortion aberration occurs reducing processing accuracy
Solution Approach 1:
The patent introduces a convex mirror as an intermediary optical element between the concave mirror and the object. This convex mirror specifically addresses distortion aberration caused by the concave mirror's focusing action. By adding this intermediary element with appropriate curvature, the system maintains beam manipulation capability while correcting distortion to improve processing accuracy.
4Device complexity
If chromatic aberration is not corrected, then the optical system remains simple, but focal point position changes causing processing defects
Solution Approach 1:
The patent achieves chromatic aberration correction by substituting the transmissive lens with a reflective system, which inherently eliminates chromatic effects. This approach provides reliable focal point stability across wavelengths while maintaining relative simplicity in the optical design, as reflection-based systems avoid the wavelength-dependent refraction issues of lens-based systems.
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 solution enhances processing quality, precision, and productivity by stabilizing the focal point across different wavelengths, improving accuracy, and allowing for effective distortion aberration correction.
Implementation Method 1
the lower surface of the first optical element is a concave mirror
Implementation Method 2
the third optical element may further include a focusing lens as a convex lens
Implementation Method 3
a second optical element including a first region reflecting the laser beam
Data Source
AI summary
A laser processing apparatus according to an exemplary embodiment includes: a light source generating a laser beam; and a light converging unit converging the laser beam to a focal point on an object to be processed, wherein the light converging unit includes a first optical element including a through hole penetrating the first optical element; a second optical element including a first region reflecting the laser beam and a second region transmitting the laser beam; and a third optical element including a focusing lens as a convex lens, a lower surface of the first optical element is a concave mirror, and an upper surface of the second optical element is convex and a lower surface thereof is concave.