Laser Wavefront Compensation Using Phase Pattern Adjustment
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Solution Overview
Problem
Existing laser processing technologies face challenges in achieving consistent results due to optical distortions in the optical path, leading to differences in processed spots between various laser processing apparatuses, which are not fully compensated by existing methods.
Innovation Solution
A laser processing apparatus and method that includes a chuck table, a laser beam applying unit with a condensing lens and a concave mirror, and a wavefront measuring unit, along with a spatial light modulator, to adjust the phase pattern based on wavefront data, using Zernike coefficients to compensate for optical distortions and achieve consistent processing results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If wavefront measurement is performed without a condensing lens, then measurement is simplified, but the measured processing spot differs from the actual processing spot, resulting in incomplete compensation of laser beam differences
Solution Approach 1:
A beam splitter is introduced as an intermediary optical component to separate the measurement path from the processing path. The beam splitter allows the measurement beam to follow the same optical path as the processing beam through the condensing lens and optical components, ensuring that the measured wavefront accurately represents the actual processing beam conditions while enabling independent measurement without interfering with the processing function
Solution Approach 2:
The laser beam path is segmented into a processing path and a measurement path using the beam splitter. The processing beam continues to the workpiece while the measurement beam is diverted to the wavefront measuring unit. This segmentation allows simultaneous independent optimization of both processing and measurement functions without mutual interference
2Device complexity
If optical distortions are not compensated, then the optical system is simpler, but different laser processing apparatus produce different processed results
Solution Approach 1:
A feedback loop is established where the wavefront measuring unit continuously measures the actual wavefront of the laser beam after it passes through all optical components including the condensing lens. The control unit compares the measured wavefront with the ideal wavefront, calculates the phase pattern required for compensation, and adjusts the spatial light modulator accordingly. This closed-loop feedback system ensures that optical distortions are dynamically compensated, achieving consistent processed results across different laser processing apparatus
Solution Approach 2:
The spatial light modulator dynamically changes the phase parameter of the laser beam by displaying calculated phase patterns on its display portion. This parameter change compensates for optical distortions introduced by the condensing lens and other optical components, transforming the distorted wavefront into an ideal wavefront that produces consistent processing results across different apparatus
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 effectively restrains differences between laser beams applied to workpieces on different apparatuses, ensuring desired processed results by iteratively adjusting the phase pattern until ideal wavefront data is achieved, thereby enhancing processing consistency.
Implementation Method 1
a concave mirror positioned to have a focal point at a focused spot of the condensing lens and having a spherical reflecting surface for reflecting the laser beam
Implementation Method 2
a beam splitter for transmitting therethrough the laser beam emitted from the laser oscillator toward the condensing lens and branching off a reflected beam of the laser beam converged by the condensing lens and reflected by the reflecting surface of the concave mirror
Implementation Method 3
a wavefront measuring unit for receiving the reflected beam reflected by the reflecting surface of the concave mirror and branched off by the beam splitter and acquiring wavefront data representing a spatial phase distribution of the laser beam
Implementation Method 4
The control unit changes a phase pattern to be displayed on a display portion of a spatial light modulator disposed between the laser oscillator and the condensing lens on a basis of the wavefront data measured by the wavefront measuring unit
Data Source
AI summary
A laser processing apparatus includes a laser beam applying unit for applying a laser beam to a workpiece, and a control unit. The laser beam applying unit includes a laser oscillator for emitting a laser, a condensing lens, a concave mirror having a focal point at a focused spot of the condensing lens and having a spherical reflecting surface, a beam splitter for transmitting therethrough the laser beam emitted from the laser oscillator toward the condensing lens and branching off a reflected beam, and a wavefront measuring unit for receiving the reflected beam and acquiring wavefront data. The control unit changes a phase pattern to be displayed on a display portion of a spatial light modulator on the basis of the wavefront data.