Laser Machining Head Focal Shift Detection With Inclined Parallel Plates
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Solution Overview
Problem
High-power laser beams cause thermal distortion in machining heads due to the thermal lens effect, and contamination from fumes or dust further complicates the issue by altering the optical absorption coefficient of optical elements, leading to focal shifts that are difficult to detect and correct.
Innovation Solution
A laser machining device is equipped with inclined parallel plates and detectors to monitor the reflected laser beam outputs from both entrance and exit surfaces, allowing for the detection and quantification of focal shifts caused by thermal lens effects, with a determination unit to identify abnormalities and a position adjuster to correct the focal shift by adjusting the long-focus lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-power laser beams are used for machining, then machining efficiency is improved, but thermal lens effect causes focal shift and reduces machining precision
Solution Approach 1:
The patent applies preliminary action by pre-positioning the parallel plate at a specific angle (e.g., 45 degrees) relative to the optical axis before laser operation begins. This predetermined configuration enables the detection system to monitor thermal lens effects in real-time and make proactive focal position adjustments, preventing precision degradation before it occurs during high-power machining operations.
Solution Approach 2:
The patent implements feedback through detectors that continuously monitor the reflected beam from the parallel plate. When thermal lens effect causes focal shift, the detection system provides real-time feedback signals that trigger automatic adjustment mechanisms to correct the focal position, thereby maintaining machining precision despite high-power operation.
2Reliability
If parallel plate is disposed closer to outgoing side to prevent fume contamination, then optical element protection is improved, but thermal distortion from contamination on plate surface increases
Solution Approach 1:
The patent uses the inclined parallel plate as an intermediary element positioned between the internal optics and the external contamination environment. The plate's specific angle and positioning create a protective barrier that redirects contaminated airflow away from sensitive optical components while the detection system monitors and compensates for any thermal effects on the plate itself.
Solution Approach 2:
The patent employs detection systems that monitor changes in the reflected beam characteristics from the parallel plate. By detecting variations in beam position, intensity, or pattern caused by thermal distortion, the system can identify and compensate for temperature-induced focal shifts, maintaining optical performance despite contamination-related heating.
3Measurement precision
If detectors are added to monitor reflected beam, then focal shift detection capability is improved, but device complexity increases
Solution Approach 1:
The patent achieves multi-functionality by using the same inclined parallel plate structure for both its primary optical function (beam direction/contamination protection) and as a reflection surface for focal shift detection. The detectors serve dual purposes by monitoring both the presence and characteristics of the reflected beam, thereby providing comprehensive optical system diagnostics without requiring separate dedicated components.
Solution Approach 2:
The patent applies self-service by utilizing the parallel plate's own reflected beam as the measurement signal for focal shift detection. The system monitors changes in the reflected beam's properties (position, intensity, angle) that naturally occur when thermal lens effect alters the incident beam characteristics, enabling the optical element to essentially monitor its own performance degradation without external intervention.
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 enables effective detection and correction of focal shifts due to thermal lens effects, preventing contamination and maintaining optimal laser output, thereby ensuring precise machining and extending the lifespan of optical components.
Implementation Method 1
a first detector that detects an output of a reflected beam from an exit end surface of the first parallel plate
Implementation Method 2
the contaminated portion absorbs the laser beam and heats the first parallel plate
Implementation Method 3
heats the first parallel plate, thereby causing thermal distortion
Implementation Method 4
a long-focus lens that focuses the laser beam which has passed through the collimate lens
Implementation Method 5
a collimate lens; a long-focus lens that focuses the laser beam which has passed through the collimate lens
Data Source
AI summary
A detector is configured to detect an output of a reflected beam from an exit end surface of a parallel plate. A determination unit is configured to determine that an abnormality occurs in the parallel plate when a detection value of the detector is smaller than a determination threshold.