Laser Focus Alignment Using Returning-Beam Feedback
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Solution Overview
Problem
Continuous operation of laser processing apparatuses leads to heat-induced distortion, causing misalignment between the workpiece surface and the focused laser beam, making it difficult to maintain proper positional relation.
Innovation Solution
A laser processing apparatus equipped with a chuck table, laser beam applying unit, beam splitter, observing unit, and adjusting unit, which includes a shearing interferometer to observe and adjust the beam's position, ensuring alignment between the workpiece surface and the focused laser spot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the laser processing apparatus is continuously operated to process the workpiece with the laser beam, then productivity is improved, but the upper surface of the workpiece and the focused spot of the laser beam are brought out of proper positional relation due to heat-induced distortion
Solution Approach 1:
The patent implements a feedback control system where the observing unit continuously monitors the returning beam to detect focal spot position deviations caused by heat-induced distortion. The adjusting unit then automatically adjusts the beam condenser position based on this feedback to maintain proper alignment between the focused spot and the workpiece surface, enabling continuous operation without precision degradation
Solution Approach 2:
The patent applies preliminary action by pre-positioning the beam condenser and establishing the initial focal spot position before processing begins. The system is configured with the beam condenser at a predetermined position to initially focus the laser beam at the correct depth, and the observing unit is ready to detect any deviations from this pre-established position
2Manufacturing precision
If the beam condenser position is adjusted to maintain focus alignment, then manufacturing precision is improved, but device complexity increases due to additional observing and adjusting units
Solution Approach 1:
The observing unit serves multiple functions: it monitors the returning beam to detect focal spot position deviations, provides feedback for the adjusting unit, and enables continuous precision maintenance. This multi-functionality justifies the addition of optical components by consolidating detection and control functions into integrated units
Solution Approach 2:
The patent introduces the returning beam as an intermediary carrier that conveys information about focal spot position. By observing the returning beam's characteristics, the system indirectly measures the position of the focused spot without requiring direct measurement of the focal point itself, simplifying the observation mechanism
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 apparatus continuously adjusts the position of the focused laser spot relative to the workpiece surface, maintaining alignment and ensuring accurate processing even as the apparatus undergoes heat-induced distortions over time.
Implementation Method 1
a plane-of-polarization rotating unit disposed between the attenuator and the beam condenser for rotating the plane of polarization of the laser beam, a beam splitter disposed between the plane-of-polarization rotating unit and the attenuator for branching a returning beam reflected from an upper surface of the workpiece
Implementation Method 2
a beam condenser for converging the laser beam emitted by the laser oscillator and applying the converged laser beam to the workpiece held on the chuck table
Data Source
AI summary
A laser processing apparatus has a laser beam applying unit including a laser oscillator for emitting a laser beam, an attenuator for regulating output power of the laser beam, a beam condenser for converging the laser beam and applying the converged laser beam to a workpiece held on a chuck table, a plane-of-polarization rotating unit disposed between the attenuator and the beam condenser for rotating the plane of polarization of the laser beam, a beam splitter disposed between the plane-of-polarization rotating unit and the attenuator for branching a returning beam reflected from an upper surface of the workpiece, an observing unit for observing the returning beam branched by the beam splitter, and an adjusting unit for adjusting the position of the beam condenser in order to focus a spot of the laser beam on the upper surface of the workpiece according to a configuration of the returning beam.