Interferometric Surface Measurement with Dynamic Signal Intensity Control
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Solution Overview
Problem
Conventional measurement apparatuses struggle to accurately measure the position of test surfaces in optical systems due to interference signal detection range limitations and environmental changes, leading to measurement errors.
Innovation Solution
An apparatus utilizing a standard unit, interferometer, and computing unit to adjust interference signal intensity and calculate surface positions, employing a Michelson interferometer with a low-coherence light source and adjustable components to ensure signal detection within the dynamic range of the detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the intensity of interference signals from both the standard surface and test surface is increased to improve signal detection, then the measurement accuracy is improved, but the detector may be saturated or the dynamic range may be exceeded
Solution Approach 1:
The patent implements dynamic adjustment of the light source intensity based on the optical path length between the light source and the test surface. The controller modifies the intensity of light emitted by the light source according to the measured optical path length, ensuring that interference signals from both the standard surface and test surface fall within the detector's dynamic range while maintaining adequate signal strength for accurate measurement.
2Measurement precision
If the optical path length is increased to improve signal separation, then the signal discrimination is improved, but the measurement time and system complexity increase
Solution Approach 1:
The patent utilizes the optical path length as a discriminating parameter to distinguish between interference signals from the standard surface and the test surface. By measuring the optical path length and using it to adjust light intensity and calculate positions, the system achieves accurate signal separation without requiring physically separated optical paths, thereby reducing measurement time and system 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
Enables precise measurement of test surface positions and surface intervals in optical systems by adjusting interference signal intensity, reducing measurement errors and enhancing accuracy.
Implementation Method 1
a first signal and a second signal in a detection unit, the first signal being a signal generated by interference between the reference light and standard light that is the test light being reflected from the standard surface, and the second signal being a signal generated by interference between the reference light and measurement light that is the test light being reflected from the test surface
Data Source
AI summary
An apparatus that measures a position of a test surface in an optical system, includes a standard unit including a standard surface, an interferometer including a light source that emits test light and reference light and a detector that acquires a first signal and a second signal, an adjustment unit configured to adjust intensity of at least one of the first signal and the second signal, and a computing unit configured to calculate the position of the test surface based on the first signal and the second signal, wherein the first signal is a signal generated by interference between the reference light and standard light that is the test light being reflected from the standard surface, and wherein the second signal is a signal generated by interference between the reference light and measurement light that is the test light being reflected from the test surface.