Laser Beam Focus Control Using Cutting Gap Image Feedback
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Solution Overview
Problem
Existing methods for determining and controlling the focus position of a processing beam, such as a laser beam, during cutting processes are prone to noise and difficulty in direct measurement, leading to challenges in maintaining a robust cutting process.
Innovation Solution
A method that records spatially resolved images of the workpiece to determine the gap width of the cutting gap and uses the beam caustic to calculate the focus position, allowing for online adjustment of the focus position to achieve a target focus position, even at varying feed speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the focus position is kept constant by controlling influencing parameters, then the cutting process stability is improved, but the adaptability to disturbances and varying feed rates deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the focus position is continuously determined during cutting by analyzing images of the cutting gap. The measured gap width is fed back to calculate and adjust the focus position dynamically, allowing the system to adapt to disturbances and varying feed rates while maintaining cutting stability.
Solution Approach 2:
The system transitions from a static focus position control to a dynamic one. The focus position is no longer kept constant but is continuously adjusted based on real-time measurements of the cutting gap width, enabling the system to adapt to changing cutting conditions and disturbances.
2Measurement precision
If direct measurement of focus position is attempted, then the measurement precision is improved, but the measurement difficulty and noise increase
Solution Approach 1:
The patent uses the cutting gap width as an intermediary parameter to indirectly determine the focus position. Instead of measuring the focus position directly, the system measures the cutting gap width (which is easier to measure with high precision using image analysis) and uses this measurement to calculate the focus position through the beam caustic relationship, thereby avoiding the difficulties of direct focus position measurement.
Solution Approach 2:
The patent replaces direct mechanical or optical focus position measurement with an image-based measurement system. By using a camera to capture images of the cutting gap and analyzing the gap width from these images, the system substitutes a difficult direct measurement with an easier indirect optical measurement that achieves higher precision.
3Device complexity
If offline measurements are used to determine focus position, then the device complexity is reduced, but the productivity and cutting accuracy deteriorate
Solution Approach 1:
The patent implements continuous focus position determination during the cutting process itself. The image capture and analysis occur continuously or at regular intervals during cutting, allowing the focus position to be determined online rather than requiring separate offline measurements. This continuous measurement approach maintains productivity while improving accuracy.
Solution Approach 2:
The cutting process itself serves the dual purpose of material separation and focus position determination. The cutting gap that is naturally formed during cutting is used as the measurement object for determining the focus position, eliminating the need for separate measurement procedures or additional complex measurement equipment.
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 method enables precise and robust determination and regulation of the focus position during cutting, reducing the need for offline measurements and improving cutting accuracy by correlating gap widths with the beam caustic, thus enhancing the measurement accuracy of the focus position.
Implementation Method 1
recording at least one spatially resolved image of an area to be monitored on a top side of the workpiece
Data Source
Figure 1~2b
Figure 3~6
AI summary
The invention relates to a method for determining a focal position of a machining beam, in particular a laser beam, relative to a workpiece (4) when machining the workpiece (4) using the machining beam, having the following steps: receiving at least one spatially resolved image (23) of a workpiece (4) region (24) to be monitored, said region comprising the cut edges (22a, b) of a cut gap (20) formed during the machining process on the upper face of the workpiece (4), ascertaining a gap width (BO) of the cut gap (20) on the upper face of the workpiece (4) using the cut edges (22a, b) in the at least one spatially resolved image (23), and determining the focal position of the machining beam (2) relative to the workpiece (4) using the ascertained gap width (BO). The invention also relates to a corresponding device.