Laser Spot Allocation for Optical Substrate Figure Correction
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Solution Overview
Problem
Existing methods for shaping optical substrates, such as thin mirrors, struggle to accurately correct figure errors and material removal rates, especially for low spatial frequency corrections on components with high aspect ratios, as traditional grinding and polishing techniques are inadequate.
Innovation Solution
A method involving the determination of a stress field with three components of stress for an optical substrate, using a computational model and calibration constants to allocate laser pulses into a minimum number of lines, which are then used to control a rotation stage, beam shaping, and laser firing parameters for surface shaping, allowing for controlled deformation and iterative correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional grinding and polishing techniques are used for figure correction, then material removal can be achieved, but the correction accuracy for low spatial frequency errors is insufficient and the process is inadequate for high aspect ratio components
Solution Approach 1:
The patent replaces traditional mechanical grinding and polishing systems with a laser-based stress figuring system. The laser induces controlled stress states within the substrate to achieve figure correction, eliminating the inadequacies of mechanical methods for high aspect ratio components and low spatial frequency errors.
Solution Approach 2:
The patent changes the fundamental parameter of material interaction from mechanical contact to optical stress induction. By controlling laser parameters (wavelength, pulse duration, intensity) and resulting stress states, the system achieves precise figure correction that is insensitive to the high aspect ratio of the workpiece.
2Manufacturing precision
If laser pulses are used to generate stress for substrate deformation, then controlled figure correction is achieved, but the complexity of determining optimal pulse positions and stress field distribution increases
Solution Approach 1:
The patent performs preliminary calculation of the stress field distribution and laser pulse position allocation before actual processing. By pre-determining the optimal pulse positions based on the desired stress states and figure correction goals, the system simplifies the real-time control complexity while maintaining high precision.
Solution Approach 2:
The patent transforms the complex stress field control problem into a manageable parameter optimization problem by defining specific stress states and their corresponding laser parameters. This parameter-based approach allows systematic determination of pulse positions without excessive system complexity.
3Manufacturing precision
If multiple laser pulses are arranged to achieve desired spot density, then accurate stress distribution is achieved, but the number of processing lines and time required increases
Solution Approach 1:
The patent optimizes the parameter of spot density to balance stress distribution accuracy with processing efficiency. By calculating the minimum number of lines required to achieve the desired stress states, the system maintains precision while maximizing material removal rate and reducing processing time.
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 approach enables precise figure correction with high material removal rates, achieving 5-15× height reduction and improving the accuracy of optical components by generating controllable stress states within the substrate, effectively addressing the limitations of traditional methods.
Implementation Method 1
An optical substrate can be deformed in a controlled way by generating stress near the substrate surfaces by creating local bending moments akin to thin film stress
Data Source
AI summary
Methods for determining laser pulse positions for shaping an optical element may comprise: determining a stress field for at least a portion of a substrate, wherein the stress field comprises at least three components of stress, wherein the stress field comprises a plurality of stress states for the at least a portion of the substrate; determining, based at least on the stress field and a calibration model, a spot density over the at least a portion of the substrate; determining, based on the spot density, a laser spot position allocation that arranges a number of laser pulses into a minimum number of lines that achieves the spot density; and causing, based on the laser spot position allocation, output of a machine program that coordinates a rotation stage, beam shaping, a translation stage, and a laser firing parameter for surface shaping of the at least a portion of the substrate.