Strained Grating Scale Thermal Deformation Detection
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Solution Overview
Problem
Existing detection devices fail to accurately detect thermal deformation, especially when it exceeds half a wavelength, leading to difficulties in normal pitch error detection of marks on a scale.
Innovation Solution
A detection device featuring a scale with a strained grating and two sensor heads mounted on a pedestal, which detects thermal deformation by analyzing the difference in positions measured by the sensor heads, allowing for accurate detection in any state, including cases where thermal deformation has already occurred.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal deformation exceeds half a wavelength (180-degree phase), then the pitch error of marks cannot be normally detected, but the detection device needs to accurately detect thermal deformation in any state
Solution Approach 1:
The detection device is divided into multiple sensor heads (at least two) arranged at predetermined intervals along the scale. Each sensor head independently detects mark positions, and the control unit compares the difference between detected positions to detect thermal deformation. This segmentation allows the system to handle large thermal deformations that would exceed the detection range of a single sensor.
Solution Approach 2:
The patent transitions from single-point detection to multi-point spatial detection by arranging sensor heads at different positions along the scale. The control unit analyzes the positional differences between multiple sensor heads to detect thermal deformation, effectively adding a spatial dimension to the detection system. This enables detection of thermal deformation regardless of its magnitude.
2Device complexity
If a single sensor is used to detect mark positions, then the device complexity is low, but the ability to detect and correct pitch errors due to thermal expansion is limited
Solution Approach 1:
Instead of using a single complex sensor, the patent employs multiple simpler sensor heads arranged at predetermined intervals. Each sensor head detects mark positions independently, and the control unit processes the difference information to detect thermal deformation. This segmentation approach achieves high measurement precision while keeping individual sensor components relatively simple.
Solution Approach 2:
The multiple sensor heads serve dual functions: they can detect mark positions for normal operation and simultaneously detect thermal deformation by comparing positional differences. This multi-functionality allows the system to maintain simplicity while achieving comprehensive detection capabilities.
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 precise detection of thermal deformation, even when it occurs after power-on or reset, by using a strained grating pattern and optical sensors to determine absolute positions and correct for thermal changes, ensuring accurate measurements regardless of deformation state.
Implementation Method 1
a scale with a strained grating; and two sensor heads mounted on a pedestal at a predetermined distance, the sensor heads detecting positions on the scale based on the grating
Data Source
AI summary
In order to provide a detection device that can accurately detect thermal deformation in any state including a case where thermal deformation has already occurred, there is provided a detection device which includes: a scale with a strained grating; and two sensor heads mounted on a pedestal at a predetermined distance, the sensor heads detecting positions on the scale based on the grating. Thermal deformation of the pedestal or the scale is detected based on a change in a difference between the positions detected by the two sensor heads.