Multiphase Lock-In Spectrometer for Fast Ambient-Light Rejection
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Solution Overview
Problem
Modulated beam scanning spectrometry is time-consuming and difficult to transport for non-laboratory measurements, and existing solutions fail to efficiently discard stray ambient optical radiation during measurements.
Innovation Solution
A multiphase lock-in spectrometer assembly that uses time modulation of optical radiation to measure spectral power distribution, employing optical lock-in detection with synchronized spectrometers to acquire and process spectra in parallel, allowing simultaneous lock-in detection at all wavelengths and rejecting non-modulated radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If modulated beam scanning spectrometry is used, then measurement precision is improved, but measurement time increases and portability decreases
Solution Approach 1:
The invention segments the continuous spectral measurement into multiple discrete wavelength channels detected simultaneously by an array detector. Each detector element measures a specific wavelength range, allowing parallel acquisition of spectral data across the entire range, eliminating the time-consuming sequential scanning process while maintaining precision through synchronized lock-in detection at each wavelength channel.
Solution Approach 2:
The invention employs periodic modulation of the optical source at a specific frequency and uses lock-in detection synchronized to this modulation frequency. This periodic action allows the system to distinguish the modulated signal from ambient light and noise, enabling precise spectral measurements to be made simultaneously across all wavelengths without the time penalty of sequential scanning.
2Measurement precision
If modulated beam scanning spectrometry is used, then measurement precision is improved, but device portability worsens
Solution Approach 1:
The invention replaces the complex scanning mechanism with a stationary array detector configuration, segmenting the spectral detection function across multiple detector elements. This eliminates moving parts and complex optical scanning mechanisms, significantly improving device portability and ease of deployment in field conditions while maintaining measurement precision through the array-based simultaneous detection approach.
Solution Approach 2:
The invention substitutes the mechanical scanning system with an optical modulation and detection system using array detectors. By replacing mechanical movement with optical modulation techniques and parallel detection, the system achieves the same measurement precision without the mechanical complexity that hindered portability.
3Device complexity
If conventional spectrometry without modulation is used, then device complexity is reduced, but ability to reject ambient light interference is lost
Solution Approach 1:
The invention introduces periodic modulation of the optical source at a known frequency and uses lock-in detection synchronized to this frequency. This allows the system to selectively detect only the modulated signal component while rejecting unmodulated ambient light and noise, effectively eliminating interference without requiring complex additional hardware beyond the modulation and synchronization capability.
Solution Approach 2:
The invention uses feedback from the known modulation frequency to drive the lock-in detection process. By continuously referencing the detection phase and frequency to the source modulation, the system maintains optimal rejection of ambient light interference while keeping the device configuration relatively simple, as the feedback mechanism is inherent in the synchronized detection algorithm.
4Measurement precision
If sequential wavelength scanning is used, then spectral resolution is improved, but productivity decreases
Solution Approach 1:
The invention segments the spectral detection across multiple array detector elements, with each element simultaneously measuring a specific wavelength channel. This parallel segmentation maintains the spectral resolution capability by preserving distinct wavelength channels while increasing productivity by measuring all channels simultaneously rather than sequentially, achieving both high resolution and high throughput.
Solution Approach 2:
The invention uses periodic modulation synchronized across all detector elements, allowing simultaneous lock-in detection at all wavelengths. This periodic synchronization maintains the ability to resolve individual wavelength components (spectral resolution) while enabling parallel measurement across the entire spectrum (increased productivity), eliminating the trade-off between resolution and throughput.
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
Enables fast and efficient measurement of complex spectra with reduced interference from ambient light, providing amplitude and phase spectra without the need for electronic lock-in amplifiers, suitable for applications like pollutant concentration and turbidity measurement.
Implementation Method 1
a collection assembly configured to collect multi-wavelength optical radiation emitted by the modulated source, wherein the collection assembly comprises at least one collection optic and is configured to output at least two identical source optical radiation beams
Implementation Method 2
two spectrometers, wherein a first spectrometer is configured to acquire a plurality of spectra on first time sections of a first source optical radiation beam, said to be in phase relative to the optical radiation collected by the collection assembly
Implementation Method 3
a lock-in assembly configured to generate at least one reference signal based on the phase and modulation frequency of the optical radiation emitted by the optical radiation source
Implementation Method 4
a low-pass filter unit configured to be applied to the plurality of spectra in order to obtain a spectral quantity of the source optical radiation beam
Data Source
AI summary
This relates to a multi-phase lock-in spectrometer assembly applied to a modulated source of multi-wavelength optical radiation, wherein the beam coming from the source is divided into two identical quadrature-modulated beams, the two beams being acquired by at least one spectrometer in order to calculate the amplitude spectrum and the phase spectrum of the modulated source of multi-wavelength optical radiation. Also disclosed are associated methods and uses.