Light Interference System with Optical Circulator for Measurement Accuracy
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Solution Overview
Problem
The existing light interference systems suffer from reduced measurement accuracy due to the intensity loss of the multiplexed reflection spectrum, which is exacerbated by the coupler's design that splits the measurement light into multiple paths, leading to a loss of 1/N in intensity, making it difficult to accurately measure temperatures and thicknesses of multiple measurement points.
Innovation Solution
The proposed light interference system incorporates a transmission device with mirrors at unused input terminals to redirect reflected lights back to the coupler, preventing antireflection termination and increasing the light intensity incident on the first input terminal, thereby enhancing measurement accuracy without altering the spectrometer's resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a coupler is used to split measurement light into multiple paths for measuring multiple points, then it is possible to easily measure temperatures of multiple measurement points, but the intensity of the multiplexed reflection spectrum is reduced to 1/N, deteriorating measurement accuracy
Solution Approach 1:
An optical circulator is introduced as an intermediary device between the coupler and the measurement points. The circulator redirects the reflected light from the measurement points back through the coupler to the spectrometer, enabling the reuse of optical paths and preventing light loss at unused coupler ports, thus maintaining measurement accuracy while preserving the ability to measure multiple points
2Device complexity
If antireflection process is performed on unused input terminals of the coupler, then the system is simplified, but the light intensity incident on the first input terminal is reduced, further deteriorating measurement accuracy
Solution Approach 1:
The optical circulator creates a feedback mechanism where reflected light from measurement points is redirected back through the coupler's unused ports. This feedback loop recovers light that would otherwise be lost, increasing the light intensity incident on the first input terminal and improving measurement accuracy without adding complex termination components
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 allows for improved measurement accuracy by increasing the light intensity incident on the first input terminal, enabling more precise temperature and thickness measurements across multiple points without compromising the spectrometer's resolution, and extends the measurable thickness range.
Implementation Method 1
a spectrometer connected to the first input terminal and configured to measure an interference intensity distribution that is an intensity distribution of the reflected lights from the first main surface and the second main surface, the interference intensity distribution being dependent on a wavelength
Implementation Method 2
multiple first collimators respectively connected to the multiple output terminals of the coupler, each being configured to emit the measurement light to the first main surface of the measurement target object and to receive reflected lights from the first main surface and the second main surface
Implementation Method 3
a transmission device provided at a side of the multiple input terminals except the first input terminal and configured to send the reflected lights from the multiple output terminals to the multiple output terminals again
Data Source
AI summary
A light interference system and a substrate processing apparatus can suppress loss of reflection spectrum. The light interference system 1 includes a light source 10, a coupler 41, multiple collimators 12A and 12B, a collimator 42, a mirror 43, a spectrometer 14, and an operation unit 15. The collimator 42 and the mirror 43 are provided at a side of multiple input terminals except a first input terminal and configured to send reflected lights from multiple output terminals to the multiple output terminals again.