Adjustable Ring Light Source for Interferometer Noise Reduction
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Solution Overview
Problem
Interferometers face challenges with coherent noises from stray light reflections and diffraction, which degrade interference patterns and reduce signal-to-noise ratio, especially with extended light sources like atomic spectrum lamps and He-Ne lasers.
Innovation Solution
A ring light source system with adjustable ring radius and width, comprising a laser light source, expander and collimator optics, binary phase grating, variable-focus optics, and spatial filter, effectively suppresses coherent noises by concentrating light energy in odd orders and filtering out stray light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a laser light source is used to provide excellent temporal coherence and spatial coherence, then the interference pattern brightness is improved, but coherent noises from stray light reflections and diffraction increase
Solution Approach 1:
The patent segments the laser beam into multiple discrete orders using a binary phase grating. The grating separates the beam into +1 and -1 orders, blocking the zero-order (undiffracted) light and higher-order stray light. This segmentation allows only the desired first-order light to reach the interferometer, eliminating coherent noises from other orders while maintaining the high coherence and brightness benefits of the laser source.
Solution Approach 2:
The patent extracts and removes harmful stray light components from the laser beam using optical elements including a binary phase grating and spatial filters. The grating extracts the useful first-order light from the beam while the spatial filter at the focal plane removes residual stray light and higher-order diffraction components, leaving only the clean interference pattern needed for high-precision measurements.
2Reliability
If an aperture is used to limit the light source dimension, then spatial coherence is improved, but effective energy entering the interferometer is significantly reduced
Solution Approach 1:
The patent replaces the traditional mechanical aperture stop with a binary phase grating that uses diffraction to control light distribution. Instead of mechanically blocking light with an aperture, the grating uses phase modulation to redirect light into specific orders. This substitution maintains spatial coherence through diffraction-based beam shaping while preserving much more energy by directing it into the desired first orders rather than blocking it entirely.
3Object-affected harmful factors
If low-coherence light sources or white light sources are used to reduce spatial coherence, then coherent noises are reduced, but the contrast of interference fringes and signal-to-noise ratio are significantly reduced
Solution Approach 1:
The patent changes the coherence parameters of the laser beam dynamically through the binary phase grating. The grating modifies the spatial frequency content of the beam, creating discrete angular separations between orders. This parameter change allows the system to maintain the high coherence and contrast of laser light while selectively removing the harmful zero-order and higher-order components that cause coherent noises, thus preserving measurement precision.
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 system enhances the accuracy and signal-to-noise ratio of interferometers by efficiently utilizing light energy and reducing coherent noise interference, making it suitable for high-accuracy measurements.
Implementation Method 1
The parallel light beam is incident perpendicularly onto the binary phase grating... the binary phase grating has diffraction light at all even orders in an extinct state... Light energy at odd orders is concentrated in ±1 orders
Implementation Method 2
followed by the variable-focus optical system. The spatial filter is positioned on a back focal plane of the variable-focus optical system... the ring radius and the ring radial width of the ring light source are adjustable by adjusting a focus length f1 of the variable-focus optical system
Implementation Method 3
The expander and collimator optical system is configured to convert a light beam from the laser light source into a parallel light beam
Implementation Method 4
The spatial filter is positioned on a back focal plane of the variable-focus optical system, and is configured to receive a ring light source... efficiently utilize the light energy and to filter out stray light at higher orders
Data Source
AI summary
A ring light source system for an interferometer with adjustable ring radius and ring radial width may comprise a laser light source, an expander and collimator optical system, an adjustable aperture, a binary phase grating, a variable-focus optical system, and a spatial filter. The expander and collimator optical system is configured to convert a light beam from the light source into a parallel light beam. The adjustable aperture is configured to adjust a diameter of the parallel light beam. The light beam with the diameter adjusted by the adjustable aperture is incident perpendicularly onto the binary phase grating, followed by the variable-focus optical system. The filter is positioned on a back focal plane of the variable-focus optical system, and is configured to receive a ring light source. The ring radius and radial width of the light source are adjustable by adjusting a focus length f1 of the variable-focus optical system.