Laser Interferometer Modulator Angle for Stable Low-Noise Sensing
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Solution Overview
Problem
Laser vibrometers face issues with unstable laser oscillation due to return light, leading to decreased signal-to-noise ratio and measurement accuracy, when a non-coaxial optical system is applied, as unmodulated components introduce noise.
Innovation Solution
A laser interferometer design with an optical modulator having a vibrator that vibrates a light reflection surface, ensuring an inclination angle of 0° < θqom < 5.7° between the normal line of the reflection surface and the incident optical axis, preventing destabilization of laser oscillation and minimizing unmodulated noise components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a non-coaxial optical system is applied to prevent return light, then laser oscillation stability is improved, but unmodulated noise components increase and signal-to-noise ratio decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the inclination angle θ of the reflection surface within a specific range (0° < θ ≤ 5.7°). This angular parameter optimization resolves the contradiction by finding the optimal balance point where the reflection surface is inclined enough to divert return light away from the laser source (improving stability) but not so inclined that it generates excessive unmodulated noise components (maintaining signal-to-noise ratio).
2Object-affected harmful factors
If the reflection surface is inclined to prevent return light, then return light entering the laser source is reduced, but unmodulated components are generated that decrease measurement accuracy
Solution Approach 1:
The patent uses parameter changes by defining a specific angular range (0° < θ ≤ 5.7°) for the reflection surface inclination. Within this range, the inclination is sufficient to redirect return light away from the laser source, eliminating harmful return light interference, while simultaneously keeping the inclination small enough to minimize the generation of unmodulated noise components that would degrade measurement accuracy.
Solution Approach 2:
The patent applies the blessing in disguise principle by converting the potentially harmful effect of return light into a beneficial configuration. By carefully controlling the inclination angle, the reflection surface redirects return light away from the laser source (turning the harmful return light path into a beneficial diversion), while the same inclination configuration is optimized to minimize unmodulated noise, thus converting what could be a double-edged sword into a purely beneficial arrangement.
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 design maintains a high signal-to-noise ratio, enabling accurate measurement of displacement and speed with improved measurement accuracy by reducing unmodulated noise, thus stabilizing laser oscillation.
Implementation Method 1
The vibrator shifts a frequency of the incident laser light based on the vibration frequency, and generates reflected laser light having a frequency different from that of the incident laser light
Implementation Method 2
A beat signal is electrically extracted by receiving light obtained by combining the scattered laser light derived from the to-be-measured object and the reference light by a photodetector
Data Source
AI summary
Provided is a laser interferometer including: a laser light source configured to emit laser light; an optical modulator including a vibrator that has a light reflection surface and vibrates in response to a drive signal, the optical modulator being configured to overlap a modulation signal on the laser light by reflecting the laser light on the light reflection surface; and a photodetector configured to receive the laser light including a sample signal derived from an object and the modulation signal, and to output a light-receiving signal. When an inclination angle θqom is defined by a normal line of the light reflection surface and an incident optical axis of the laser light incident on the light reflection surface, the following Relationship (1) is satisfied.0[deg]<θqom<5.7[deg] (1)