Interferometer Optical Path Protection Against Refractive Index Errors
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Solution Overview
Problem
Laser interferometer systems face measurement errors due to changes in refractive index caused by temperature and pressure variations, especially when the optical path is not fully sealed, leading to errors in the irradiation position of the measuring light on the object to be measured.
Innovation Solution
An interferometer system with an optical path protecting member that surrounds the laser light source and emission opening, using a sealing member to prevent air flow and temperature changes, and a temperature controller to maintain a constant internal temperature, reducing the occurrence of measurement errors by minimizing angle changes in the laser light path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical path is sealed with a sealing pipe to prevent pressure variations, then measurement precision is improved, but a measurement error occurs when a portion open to atmosphere is present due to refractive index changes from temperature variations
Solution Approach 1:
The patent applies local quality by providing thermal insulation specifically at the emission opening where the laser light exits, rather than insulating the entire optical path. The insulating member is placed locally at the critical position where temperature variations cause refractive index changes, blocking airflow and thermal effects only where needed to maintain measurement precision without requiring full sealing of the optical path.
2Reliability
If the laser light source is heated to stabilize wavelength, then reliability is improved, but temperature distribution changes cause refractive index interface changes and measurement errors
Solution Approach 1:
The patent extracts the thermal management function from the overall optical path control by providing a dedicated insulating member at the emission opening. This separates the wavelength stabilization heating (which occurs at the light source) from the measurement path, blocking the harmful thermal effects at the emission point while allowing the light source to maintain its operating temperature for wavelength stability.
3Ease of operation
If air flow occurs in the common optical path, then ease of operation is improved, but the angle of laser light changes due to refractive index distribution changes
Solution Approach 1:
The patent applies preliminary anti-action by placing the insulating member at the emission opening to preemptively block airflow and thermal effects before they can enter the optical path. This prevents refractive index changes and optical axis deviations before they occur, maintaining measurement precision while allowing the rest of the optical path to remain open and easy to operate.
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 effectively reduces measurement errors by blocking air flow and maintaining a stable temperature, thereby minimizing the impact of refractive index changes and ensuring accurate position measurement of the object to be measured.
Implementation Method 1
when any one of temperature, pressure, and humidity changes in an optical path through which either the measuring light or the reference light passes, the refractive index of air changes
Implementation Method 2
The temperature of the laser light source is typically controlled by using a heater in order to stabilize the wavelength of laser light
Implementation Method 3
detects an interference signal generated by superposition of the measuring light returned by reflection from the object to be measured and the reference light
Data Source
AI summary
Provided is an interferometer system that irradiates an object to be measured with measuring light to thereby measure the position of the object to be measured. The interferometer system includes a laser light source; an interferometer configured to separate laser light emitted from an emission opening of the laser light source into the measuring light and reference light; and an optical path protecting member configured to surround an optical axis such that the laser light passes through the inside thereof and of which one opening is in contact with the emission opening.