Resonant 1D Mirror Assembly With Tunable Scan Frequency
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Solution Overview
Problem
Existing mirror assemblies in inspection systems are limited by size, inertia, and dynamic performance, restricting high-speed and adjustable rotation of large mirrors, which affects inspection performance and adaptability to different scan speeds.
Innovation Solution
A mirror assembly system utilizing a support member, fulcrum, voice coil, and adjustable flexible extension members and masses to oscillate a mirror at synchronized angular velocities with the stage's linear velocity, allowing for high-speed and adjustable rotation of large mirrors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the mirror size is increased to improve inspection coverage and reduce blurring, then the mirror's inertia grows exponentially, causing dynamic performance (speed, acceleration, stability) to drop significantly
Solution Approach 1:
The patent utilizes resonant vibration of the mirror assembly at its natural frequency to achieve high angular velocities. By driving the mirror at resonance, the system obtains high local angular velocities without requiring large inertial mirrors, thus resolving the contradiction between mirror size and speed performance
Solution Approach 2:
The patent changes the operating parameters by tuning the mirror assembly to operate at its resonant frequency. This parameter change enables the system to achieve high-speed performance with smaller mirrors, as the resonant oscillation amplifies the motion response without requiring proportionally larger actuating forces
2Speed
If a resonant mirror is used to achieve high local angular velocities, then the mirror can operate at a specific fast frequency, but working outside this frequency is impossible due to lack of gain
Solution Approach 1:
The patent employs a dynamically adjustable mirror assembly where the resonant frequency can be tuned by changing the effective length of flexible extension members. This allows the system to adapt to different inspection parameters and scan speeds while maintaining high angular velocity performance, resolving the frequency adaptability issue
3Shape
If a piezo-based fast steering mirror is used to achieve large angular range of motion, then a long stack of piezo elements is required, but the length of the stack compromises motion dynamics
Solution Approach 1:
The patent uses resonant vibration to achieve large angular ranges of motion without requiring long piezo stacks. By operating at the natural frequency of the mirror assembly, the system achieves amplified motion response with compact actuators, maintaining fast motion dynamics while obtaining large angular excursions
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 high-resolution imaging by synchronizing the mirror's angular velocity with the stage's linear velocity, improving image quality and adaptability to various scan speeds without blurring, enhancing defect detection in semiconductor substrates and other workpieces.
Implementation Method 1
a voice coil disposed on the base member on one side of the fulcrum and connected to one end of the support member, and a processor configured to send an excitation signal to the voice coil, which causes the support member to oscillate relative to the fulcrum
Implementation Method 2
Another type of mirror assembly is a resonant mirror, which operates at a specific fast frequency based on the spring/mass ratio of the mirror assembly and can obtain high local angular velocities
Data Source
AI summary
The system includes a support member configured to support a mirror, a fulcrum configured to centrally support the support member, and a base configured to support the fulcrum. A voice coil is disposed on the base member on one side of the fulcrum and connected to one end of the support member. A processor is configured to send an excitation signal to the voice coil, which causes the support member to oscillate relative to the fulcrum.