Interferometer Thin Retarder Volume Reduction
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Solution Overview
Problem
Conventional interferometers face challenges with cyclic errors and sensitivity to angular orientation changes, leading to reduced accuracy in displacement measurements, particularly in lithography systems where precise control of beam overlap and alignment is critical.
Innovation Solution
The implementation of thin quarter-wave or half-wave retarders, secured directly to the interferometer surfaces without a glass cover plate, reduces the physical volume and enhances the stability of interferometers, allowing for closer placement of multiple interferometer units and improved beam alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional thick retarders with glass cover plates are used, then structural stability is maintained, but the physical volume and footprint of the interferometer increase
Solution Approach 1:
The patent replaces conventional thick glass cover plate retarders with thin-film retarders deposited directly on optical surfaces. This thin-film approach reduces the physical volume and footprint of the interferometer while maintaining the necessary optical functionality and structural stability through the thin-film deposition technique.
Solution Approach 2:
The patent extracts and eliminates the glass cover plate component from the traditional retarder assembly. By removing this unnecessary intermediate layer, the design achieves a more compact form factor while the retarder function is maintained through direct deposition on the optical surface.
2Area of stationary object
If multiple interferometer units are placed closer together, then the footprint is reduced, but beam alignment and overlap become more difficult to control
Solution Approach 1:
The thin-film retarders enable closer spacing of multiple interferometer units by reducing the overall footprint of each unit. The direct deposition on optical surfaces provides precise control over the retarder properties, maintaining beam alignment accuracy even when units are placed in closer proximity.
3Volume of moving object
If thin retarders without glass cover plates are used, then the footprint is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent replaces the mechanical assembly of separate retarder and glass cover plate components with a thin-film deposition process. This substitution of mechanical assembly with a deposition process actually simplifies manufacturing by reducing the number of discrete components and assembly steps, despite the advanced deposition technology required.
4Measurement precision
If conventional interferometer configurations are used, then cyclic errors occur due to polarization misalignment, but measurement accuracy is compromised
Solution Approach 1:
The thin-film retarders provide precise control over polarization state with thin-film deposition techniques enabling accurate control of film thickness and optical properties. This precise control minimizes polarization misalignment and reduces cyclic errors in displacement measurements, improving measurement accuracy.
Solution Approach 2:
The patent changes the physical and optical parameters of the retarder by using thin-film deposition with controlled thickness and material properties. This parameter control optimizes the polarization manipulation to minimize cyclic errors while maintaining measurement precision.
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 configuration reduces the footprint of interferometer systems, increases accuracy by minimizing cyclic errors and sensitivity to angular changes, and simplifies manufacturing while maintaining high reliability and uniformity.
Implementation Method 1
The thin retarder can include a linearly photopolymerizable polymer (LPP) material coated onto at least a portion of the surface of the retroreflector to form a film that changes a polarization direction and/or an ellipticity of at least one of the input light beam and the output light beam
Implementation Method 2
a retroreflector having a surface for receiving an input light beam that is retro-reflected to form an output light beam
Implementation Method 3
The thin retarder can include a linearly photopolymerizable polymer (LPP) material coated onto at least a portion of the surface of the retroreflector
Data Source
AI summary
An apparatus includes an interferometer having a polarizing beam splitter to split an input beam into a measurement beam and a reference beam, the measurement beam contacting a measurement object, the reference beam contacting a reference object. The interferometer includes at least one thin retarder on a surface of the interferometer.