Non-Circular Laser Beam Optical System for Uniform Material Processing
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Solution Overview
Problem
Current optical systems fail to effectively transmit and focus non-circular laser beams to the desired location with the required intensity, particularly in high-power applications like welding and heat treatment, where a uniform beam is necessary for efficient material processing.
Innovation Solution
An optical system comprising a combination of five spaced lenses, including an F-theta lens, is used to form and adjust the image of a non-circular fiber core, ensuring the image coincides with the beam waist and achieves the desired spot size and intensity at the focal plane, adhering to the equation A/B=F4/F5, where A and B are the initial and desired spot sizes, and F4 and F5 are the respective focal lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a standard telescope system is used to transmit non-circular laser beams, then the beam can be transmitted to the workpiece, but the image of the fiber core does not coincide with the beam waist, resulting in non-uniform intensity distribution
Solution Approach 1:
The optical system is divided into three functional segments: a collimation lens (first optical element) that converts divergent beam to collimated beam, a beam shaping lens (second optical element) that forms the image at the waist location, and an F-theta lens (third optical element) that provides final focusing. This segmentation allows each element to be optimized for its specific function, achieving precise image-waist coincidence while maintaining manageable system complexity
Solution Approach 2:
The patent introduces an intermediary collimation lens between the fiber output and the beam shaping lens. This intermediary element transforms the divergent beam from the fiber core into a collimated beam, which then allows the subsequent beam shaping lens to form a sharp image at the desired waist location. Without this intermediary collimation step, direct focusing would result in poor image quality and incorrect positioning
2Manufacturing precision
If the image is formed at the focal plane to achieve desired spot size, then the spot size requirement is met, but the image does not coincide with the beam waist, reducing intensity
Solution Approach 1:
The patent carefully selects and adjusts critical parameters including the focal length of the beam shaping lens (f2), the focal length of the F-theta lens (f3), and the spacing between optical elements (d1, d2, d3). By optimizing these parameters, the system achieves a configuration where the image is simultaneously formed at the focal plane (meeting spot size requirements) and coincides with the beam waist (maximizing intensity). The key relationship is f3 = d2 + d3, which ensures proper positioning
3Productivity
If circular fiber cores are used, then standard optical systems work effectively, but non-circular beam shapes required for uniform material processing cannot be achieved
Solution Approach 1:
The patent embraces asymmetry by using non-circular fiber cores (rectangular, elliptical, or other asymmetric cross-sections) to generate corresponding non-circular laser beams. The optical elements are specifically designed to preserve and utilize this asymmetric beam shape rather than attempting to circularize it. This asymmetric approach enables uniform energy distribution across the material surface during lateral movement, improving material processing efficiency for applications like welding and heat treatment
4Device complexity
If back reflected light is allowed to enter the source, then simpler optical paths can be used, but high power backreflected light damages the MOPA system
Solution Approach 1:
The patent extracts the beam shaping and focusing functionality from the traditional isolator assembly and implements it as a separate, dedicated optical system. This extracted system processes the forward-propagating beam to achieve proper image formation at the waist, while the isolator handles only the back-reflection protection function. This separation allows the main optical path to remain relatively simple while ensuring system reliability through proper beam conditioning before the workpiece
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 system successfully delivers a non-circular laser beam with the desired intensity to the workpiece, ensuring effective material processing by accurately placing the image of the fiber core within the Rayleigh range of the laser beam, enhancing processing uniformity and efficiency.
Implementation Method 1
The lenses are spaced apart along a light path and have respective optical characteristics which allow first to place a non-circular image and waist in a focal plane of one of intermediary lenses, and then modify the spot size of the image to the desired one
Implementation Method 2
The desired spot size of the image corresponds to the beam intensity sufficient to effectively treat a workpiece
Data Source
AI summary
An optical system for forming a final image of a non-circular light source on a workpiece with a desired non-circular cross-section and desired size B includes a plurality of spaced lenses. The plurality of lenses are arranged with spaced upstream and downstream lenses which are configured to transmit the beam emitted by the light source. The optical system is configured with an F-theta lens spaced downstream from the downstream lens and converging the beam incident thereon so that the beam has a final waist. The F-theta and downstream lenses are spaced apart so thatF4Fth=AB,wherein F4 a positive focal length of the downstream lens, Fth is the negative focus of the F-theta lens, B is the desired size of the final image, and A is a size of a preliminary noncircular image of the source different from the desired size B.