Variable Retarder Plate Tipping Mechanism for Ellipsometer Precision
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Solution Overview
Problem
Rotating Polarizer and Rotating Analyzer Ellipsometer systems face challenges in accurately monitoring DELTA values near 0.0 and 180 degrees, and Modulation Element Ellipsometers struggle with PSI values near 45 degrees, with existing Variable Retarder systems being expensive and cumbersome due to the need for two separate rotation producing means.
Innovation Solution
A system that enables tipping of a retarder plate about at least two axes using only one tip producing means, comprising a hollow shaft rotation producing mechanism, a mounting system, and a bracket to secure and tip the retarder plate, allowing for orthogonal axis orientations without concentric rings, utilizing a hollow shaft stepper motor for efficient rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two separate rotation producing means are used to tip the variable retarder about orthogonal axes, then the data acquisition capability is improved in problematic angle regions, but the system becomes expensive and cumbersome
Solution Approach 1:
The patent combines two separate rotation producing means into a single mechanism that can tip the variable retarder about orthogonal axes sequentially. The first rotation producing means tips the retarder about a first axis, and the second rotation producing means tips it about a second orthogonal axis, but both are integrated into one cohesive mounting system rather than two independent systems.
Solution Approach 2:
The system dynamically adjusts the orientation of the variable retarder by sequentially applying tipping motions about orthogonal axes. The rotation producing means can independently control the tipping angle about each axis, allowing dynamic adaptation to different measurement requirements while maintaining a compact structure.
2Measurement precision
If two separate rotation producing means are used to tip the variable retarder, then the measurement accuracy is enhanced, but the cost increases
Solution Approach 1:
The patent integrates two rotation producing means into a single manufacturable assembly with common mounting structures, shared mechanical supports, and unified alignment mechanisms. This merging reduces the total number of independent components that need to be manufactured and assembled, thereby reducing overall manufacturing cost while maintaining the capability to tip about orthogonal axes.
Solution Approach 2:
The mounting system is designed with universal features that allow the same structural elements to serve multiple functions - supporting both rotation producing means, providing common alignment references, and facilitating the sequential tipping motion. This multi-functionality reduces the need for specialized components for each axis, lowering manufacturing complexity and cost.
3Device complexity
If concentric rings are used to mount the variable retarder, then the tipping mechanism is simplified, but the device becomes cumbersome and expensive
Solution Approach 1:
The patent extracts the essential tipping function from the concentric rings mounting approach and implements it through a more straightforward mechanism. Instead of using complex concentric ring structures, the invention uses direct mounting means that secure the variable retarder and enable tipping about orthogonal axes through simpler mechanical arrangements.
Solution Approach 2:
The patent employs simpler, more economical mounting components in place of expensive concentric rings. The mounting means use standard mechanical elements that are easier and cheaper to manufacture, while still achieving the required tipping functionality. The design prioritizes cost-effective solutions over premium mechanical structures.
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 solution enhances data acquisition capability in ellipsometers by allowing precise tipping of the retarder plate about offset axes, improving data accuracy in problematic angle regions with reduced complexity and cost compared to prior systems.
Implementation Method 1
a hollow shaft stepper motor for efficient rotation
Implementation Method 2
a bracket comprising means for accessibly securing a retarder plate thereto and means for effecting tipping of said retarder plate
Implementation Method 3
Berek-type Variable Retarders
Data Source
AI summary
A system for implementing Berek-type variable retarder plate tipping capability in two orthogonal directions via tipping about a single axis, in combination with a means for rotating the orientation of the axis, having application in ellipsometer and polarimeter and the like systems.