Encoder Scale Calibration via Local Deformation Detection
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Solution Overview
Problem
Existing encoder calibration methods are inefficient due to surface deformation of scales, leading to detection errors and inaccurate positioning of stages in exposure apparatuses, especially when partial deformation occurs.
Innovation Solution
A calibration method that measures deformation amounts of scale surfaces, specifies correction ranges based on these measurements, and determines correction values to adjust encoder detection values, thereby improving positioning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration is performed over the entire surface of the scale, then detection errors in non-deformed portions are corrected, but calibration efficiency decreases due to unnecessary calibration in already accurate regions
Solution Approach 1:
The patent applies local quality by performing calibration only in specific regions where deformation is detected rather than uniformly across the entire scale surface. The calibration process is localized to areas with detected surface deformation, making the calibration process more efficient while maintaining accuracy where needed.
Solution Approach 2:
The patent uses partial action by performing calibration only in the necessary portions of the scale surface where deformation exceeds a threshold, rather than calibrating the entire surface. This partial calibration approach reduces unnecessary calibration operations in already accurate regions while maintaining overall measurement precision.
2Ease of operation
If the scale surface deforms, then the encoder can still operate, but detection errors occur making accurate stage positioning difficult
Solution Approach 1:
The patent applies parameter changes by measuring and correcting the scale surface deformation parameters. The system detects changes in the scale surface shape and uses these parameter changes to calculate correction values that compensate for the deformation, thereby maintaining positioning accuracy despite scale deformation.
Solution Approach 2:
The patent uses feedback by measuring the actual scale surface deformation and using this information to generate correction values. The deformation measurement feedback is fed into the correction value calculation process, which then adjusts the encoder readings to compensate for the detected deformation, maintaining accurate stage positioning.
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 method effectively reduces detection errors by accurately calibrating encoders, ensuring precise stage positioning and maintaining calibration efficiency even with partial scale deformation.
Implementation Method 1
a light receiving unit which radiates the surface of the scale with light and receives reflected light, and can detect the relative position between the scale and the light receiving unit
Data Source
AI summary
The present invention provides a method for calibrating an encoder which includes a scale and a light receiving unit configured to receive light reflected by the scale, and detects a change in relative position between the scale and the light receiving unit, the method comprising a measurement step of measuring a deformation amount of a surface shape of the scale, a specifying step of specifying, based on a measurement result in the measurement step, a range which includes a portion of a surface of the scale, where the deformation amount exceeds a threshold, and within which a detection value of the encoder is corrected, and a determination step of determining a correction value for correcting the detection value of the encoder within the range specified in the specifying step.