Laser Focus Control Using Wavefront Modulation for Deeper Autofocus
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Solution Overview
Problem
Existing laser dicing devices have a limited range for autofocus processing due to the fixed relationship between the converging points of processing and measurement laser light, which restricts the depth range of processing.
Innovation Solution
A laser processing device that uses a spatial light modulator to independently adjust the converging point of the processing laser light based on the distance between the processing and measurement laser light converging points and the desired processing depth, allowing for a wider range of autofocus processing without the need for complex lens configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a focus lens group with movable lenses is used to independently change the converging point of AF laser light, then the range of autofocus processing is enlarged, but the device complexity increases due to multiple lenses requiring precise optical axis adjustment and mechanical actuators
Solution Approach 1:
The patent replaces the mechanical lens movement system with an optical modulation approach. A spatial light modulator (SLM) is used to modulate the wavefront of the processing laser light, enabling the converging point to be changed independently from the AF laser light converging point without mechanical actuators or movable lenses. This substitution of mechanical systems with optical modulation achieves the same functional goal while dramatically reducing device complexity.
Solution Approach 2:
The spatial light modulator acts as an intermediary element between the laser light source and the workpiece. By introducing the SLM into the optical path, the system can independently control the converging point of processing laser light while keeping the AF measurement system unchanged. This intermediary device enables independent adjustment without requiring complex mechanical lens groups or precise optical axis adjustments of multiple lenses.
2Device complexity
If the converging point of processing laser light and measurement laser light are kept at a constant distance, then the optical system is simplified, but the processing depth range is limited
Solution Approach 1:
The patent introduces dynamic control of the processing laser light converging point position through wavefront modulation by the spatial light modulator. While the AF measurement system maintains a fixed converging point for stable surface displacement measurement, the processing laser light converging point can be dynamically adjusted to different depths within the workpiece. This dynamic adjustment capability enables processing at various depths while keeping the measurement system simple and fixed.
Solution Approach 2:
The patent changes the wavefront parameters of the processing laser light using the spatial light modulator to independently control the converging point position. By modulating the wavefront phase or amplitude distribution, the system can shift the converging point depth without physically moving any optical components. This parameter-based control allows the processing depth to be varied while maintaining a constant-distance relationship simplification in the overall optical system design.
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
Enables a broader range of autofocus processing capabilities while maintaining a simple configuration, improving the accuracy and depth range of laser processing without the mechanical complexity of moving lens groups.
Implementation Method 1
a spatial light modulator configured to modulate the laser light according to a modulation pattern between the laser light source and the converging unit
Implementation Method 2
a converging unit that converges the laser light toward the object to be processed to form a first converging point and converges the measurement light toward the object to be processed to form a second converging point
Implementation Method 3
a measurement part configured to measure displacement of an entrance surface according to reflected light of the measurement light on the entrance surface of the laser light and the measurement light in the object to be processed
Data Source
AI summary
A laser processing device including a laser light source that outputs laser light, a measurement light source that outputs measurement light, a converging unit that converges the laser light toward an object to be processed to form a first converging point and converges the measurement light toward the object to be processed to form a second converging point, a measurement part for measuring displacement of an entrance surface according to reflected light of the measurement light on the entrance surface of the laser light and the measurement light in the object to be processed, and an adjustment unit that adjusts a position of the first converging point in a direction intersecting the entrance surface according to a measurement result of the displacement of the entrance surface.