Monolithic Encoder Head Facets Redirect Beams
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Solution Overview
Problem
Interferometric encoder systems for lithography applications require complex optical designs with multiple components to redirect and combine diffracted measurement beams, leading to increased costs and complexity, while existing solutions do not efficiently utilize light energy and often require multiple separate input beams for position measurements.
Innovation Solution
A compact encoder head design utilizing a monolithic optical component with multiple facets, which receives and redirects once-diffracted measurement beams back onto the encoder scale to produce twice-diffracted beams, allowing for interference signal detection and phase-based position determination with reduced optical elements and lower noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple separate optical components are used to redirect and combine diffracted measurement beams, then the encoder system can achieve position measurement functionality, but the device complexity and cost increase
Solution Approach 1:
The patent combines multiple optical components (beam splitter, mirrors, retroreflector) into a single integrated optical assembly. This assembly redirects diffracted measurement beams and combines them with reference beams while maintaining measurement precision, thereby reducing device complexity and the number of separate optical components
Solution Approach 2:
The integrated optical assembly performs multiple functions simultaneously: it splits beams, redirects diffracted beams, combines measurement beams with reference beams, and enables interference signal detection. This multi-functionality reduces the need for separate components while maintaining measurement capabilities
2Measurement precision
If multiple separate optical components are used to redirect beams, then beam combination is achieved, but light energy is not efficiently utilized and noise increases
Solution Approach 1:
The integrated optical assembly minimizes the number of beam redirection interfaces, reducing light energy loss at each interface. By combining beam splitting, redirection, and combination functions in one assembly, the system efficiently utilizes light energy and reduces noise, improving signal quality
3Device complexity
If a compact encoder head design is implemented with a monolithic optical component, then device complexity and cost are reduced, but the ability to redirect and combine multiple diffracted beams may be compromised
Solution Approach 1:
The monolithic optical component is designed with multiple facets that enable it to perform multiple functions: receiving incident beams, redirecting diffracted beams back onto the encoder scale, and combining beams. This multi-functionality maintains beam redirection capability while reducing device complexity
Solution Approach 2:
The patent uses a monolithic component with multiple facets arranged in three-dimensional space to achieve complex beam redirection paths. This spatial arrangement allows the single component to perform functions that would otherwise require multiple separate components, maintaining versatility while reducing complexity
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 solution simplifies the encoder system design, reduces the number of optical elements, and efficiently uses light energy, enabling precise position measurements with lower noise and cost, while maintaining accuracy in lithography applications.
Implementation Method 1
The encoder scale is positioned in a path of the once-diffracted measurement beams to produce the twice-diffracted measurement beams
Implementation Method 2
the multiple facets being arranged to: i) receive multiple once diffracted measurement beams from a surface of the encoder scale; and ii) redirect the multiple once-diffracted measurement beams back towards the surface of the encoder scale
Implementation Method 3
the encoder head being configured to combine each twice-diffracted measurement beam of multiple twice-diffracted measurement beams with a corresponding reference beam to form multiple output beams
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3B
AI summary
An encoder system includes an encoder scale and an encoder head, in which the encoder head is configured to combine each twice-diffracted measurement beam of multiple twice-diffracted measurement beams with a corresponding reference beam to form multiple output beams, where the encoder head includes a monolithic optical component having multiple facets, the multiple facets being arranged to: receive multiple once-diffracted measurement beams from a surface of the encoder scale; and redirect the multiple once-diffracted measurement beams back towards the surface of the encoder scale, the encoder scale being positioned in a path of the once-diffracted measurement beams to produce the twice-diffracted measurement beams.