Laser Line Homogenization Optics for Scalable Deep-Focus Illumination
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Solution Overview
Problem
Existing laser systems face challenges in providing a line-shaped intensity distribution with a large aspect ratio and deep focus, while maintaining homogeneity along the line and allowing for scalable line length, particularly in applications like laser processing and microelectronic device production.
Innovation Solution
A beam transformation unit using a transparent monolithic plate-shaped optical element with reflective surfaces re-sorts input beam segments to achieve reduced spatial and temporal coherence, combined with a homogenization and focusing unit that forms a top-hat intensity distribution, enabling efficient line illumination and scalable line length through stitching of laser lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional laser systems use standard optical configurations for line generation, then the system structure is simple, but the intensity distribution homogeneity along the line is insufficient
Solution Approach 1:
The beam is divided into multiple beam segments that are processed independently through the optical system. Each segment undergoes specific transformations including reflection, refraction, and spatial redistribution, allowing independent optimization of intensity distribution across different regions of the beam, ultimately achieving homogeneous line-shaped intensity distribution.
Solution Approach 2:
A beam transformation unit comprising multiple optical elements (reflective surfaces, refractive surfaces, and intermediate optical components) is introduced as an intermediary between the laser source and the target. This intermediary system transforms the initial beam characteristics into the desired line-shaped homogeneous intensity distribution without requiring direct modification of the laser source.
2Shape
If the aspect ratio of the beam is increased to achieve a more pronounced line shape, then the line shape quality improves, but the depth of focus in the direction of the smaller beam diameter decreases
Solution Approach 1:
The optical system introduces additional dimensional transformations by using multiple reflection and refraction surfaces oriented at different angles. This multi-dimensional approach allows independent control of beam parameters in different spatial directions, achieving both high aspect ratio for line shape and sufficient depth of focus by manipulating the beam propagation in multiple dimensions simultaneously.
Solution Approach 2:
The system dynamically adjusts optical parameters including incidence angles, reflection angles, and refractive indices through the multiple optical surfaces. By changing these parameters across different beam segments, the system achieves optimal balance between aspect ratio and depth of focus, creating a line-shaped beam with both high geometric fidelity and extended focal depth.
3Area of stationary object
If the line length is extended to cover larger processing areas, then the processing coverage improves, but the homogeneity of intensity distribution along the line deteriorates
Solution Approach 1:
The extended line beam is constructed by segmenting the processing area and using multiple optical paths to cover different segments. Each segment is independently optimized for homogeneous intensity distribution, and the segments are combined to form the complete extended line, maintaining homogeneity across the entire processing area.
Solution Approach 2:
The beam transformation unit is designed with universal optical elements that can handle multiple beam segments simultaneously. The same optical principles and components are applied across all segments, ensuring consistent intensity distribution characteristics throughout the extended line length, enabling scalable processing coverage while maintaining uniformity.
4Manufacturing precision
If multiple optical elements are added to improve beam homogeneity and line shape, then the beam quality improves, but the device complexity and alignment difficulty increase
Solution Approach 1:
Multiple optical functions (reflection, refraction, beam shaping, and homogenization) are merged into an integrated beam transformation unit. The optical elements are arranged in a compact configuration where they work together as a unified system, reducing the overall number of separate components and simplifying alignment while achieving superior beam quality through the combined effect of all elements.
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 achieves high homogeneity and scalability in laser line illumination, reducing interference and enhancing beam quality, suitable for high-throughput laser processing applications such as annealing and recrystallization of thin films.
Implementation Method 1
the front reflecting surface area and the back reflecting surface area guide a plurality of input beam segments of the input laser beam, after having entered the transformation optics through the input surface area, by reflection within the transformation optics to exit through the output surface area
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A laser system (1) is configured for providing a laser line (L) in a working plane (WP) for line illumination of an object (7). The laser line (L) extends in a first direction (x) over a significant length and in a second direction (y) over a small extent. The laser system (1) comprises a laser source (3) for providing a laser beam (3A) as basis for an elongated input laser beam (13A) propagating along a propagation direction (z), and a homogenization and focussing unit (60) for homogenizing the elongated laser beam (13A) to form the laser line (L). The laser system (1) is in particular suitable for providing a laser line (L) that can be stitched to another laser line (L') of a respective further laser system (1').