Spectroscopic Device Stray Light Suppression via Fourier Interference
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Solution Overview
Problem
Spectroscopic devices face challenges in detecting weak light components such as Raman scattered light, luminescence, and harmonics due to the influence of stray light, particularly when using strong light sources like lasers.
Innovation Solution
A spectroscopic device configuration that includes a light source unit, a Fourier spectroscopic unit, a wavelength dispersion spectroscopic unit, and a control device. The control device extracts the signal light component by removing stray light through image processing of the detection results from the wavelength dispersion spectroscopic unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a strong light source such as a laser is used for spectroscopy, then the light intensity for detection is improved, but the influence of stray light increases making it difficult to detect weak light components
Solution Approach 1:
The patent divides the detection process into two separate detection paths: one for detecting the strong excitation light and another for detecting the weak signal light (Raman scattered light, luminescence, or harmonics). By segmenting the detection function, the system can independently optimize each detection channel, allowing the use of strong laser light while simultaneously detecting weak signal components without mutual interference.
Solution Approach 2:
The patent introduces a wavelength dispersion element as an intermediary component that spatially separates different wavelength components of light. This intermediary device disperses the combined light containing both strong excitation light and weak signal light into their respective wavelength components, enabling the detection system to distinguish and detect weak signals despite the presence of strong stray light.
2Measurement precision
If spectroscopy using a diffraction grating or Fabry-Perot interferometer is repeated multiple times, then frequency resolution is improved and laser light influence is reduced, but the measurement time increases and wide wavelength range cannot be detected at once
Solution Approach 1:
The patent segments the spectrum detection into multiple spatial channels using a wavelength dispersion element, allowing simultaneous detection of different wavelength ranges. Combined with the two-detector configuration, this enables parallel acquisition of spectral data across a wide wavelength range, eliminating the need for repeated sequential measurements while maintaining high frequency resolution.
Solution Approach 2:
The patent transitions from temporal multiplexing (repeated measurements over time) to spatial multiplexing (simultaneous detection across different spatial positions). By using the wavelength dispersion element to spatially separate wavelength components and multiple detectors to simultaneously capture signals, the system achieves wide wavelength range detection and high frequency resolution without increasing measurement time.
3Object-affected harmful factors
If a filter using interference effect of dielectric multilayer film is used to reduce laser light influence, then the stray light suppression is improved, but the device complexity increases
Solution Approach 1:
The patent employs a wavelength dispersion element that performs multiple functions simultaneously: it disperses wavelength components, spatially separates strong excitation light from weak signal light, and enables wide wavelength range detection. This multi-functional approach replaces the need for multiple specialized filters and complex optical paths, reducing overall device complexity while achieving effective stray light suppression.
4Area of stationary object
If harmonics are detected using a diffraction grating, then the wavelength dispersion is achieved, but short wavelength side of low-order diffracted light and long wavelength side of high-order diffracted light are diffracted in the same direction making wavelength selection difficult
Solution Approach 1:
The patent segments the detection of different wavelength components into distinct spatial positions using the wavelength dispersion element. By combining this with multiple detectors positioned at different locations, the system can simultaneously and independently detect harmonics across different wavelength ranges without overlap or confusion, achieving both wide wavelength coverage and precise wavelength selection.
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 enables the detection of light components over a wide wavelength range with reduced stray light influence, improving the accuracy of Raman scattering, luminescence spectroscopy, and harmonic observation.
Implementation Method 1
generate a pair of light beams with any time delay, and output first output light obtained by causing the pair of light beams to interfere with each other
Implementation Method 2
detect second output light obtained by dispersing the received first output light according to a wavelength
Data Source
AI summary
A spectroscopic device according to the present disclosure includes: a light source unit configured to output signal light generated from a sample; a Fourier spectroscopic unit configured to receive the signal light, generate a pair of light beams with any time delay, and output first output light obtained by causing the pair of light beams to interfere with each other; a wavelength dispersion spectroscopic unit configured to detect second output light obtained by dispersing the received first output light according to a wavelength; and a control device configured to extract a component of the signal light in the second output light based on a detection result of the second output light.