Spectrometer Multi-Wavelength Detection via Modulated LEDs
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Solution Overview
Problem
Existing spectrometer technologies face limitations in simultaneously detecting multiple wavelengths, particularly with complex systems using tunable excitation sources and lock-in detection, which restricts their applicability in various measurement applications.
Innovation Solution
The use of modulated light sources with different wavelengths in combination with a Fabry-Perot filter allows for simultaneous processing and demodulation of signals from multiple orders, enabling simultaneous detection of multiple wavelengths using a wideband detector, suitable for a wide spectral range from UV to IR, and applicable for both absorption and reflection measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotating filter disc is used to select wavelength bands, then wavelength selection is achieved, but the detection of multiple wavelengths cannot be simultaneous
Solution Approach 1:
The patent applies periodic modulation to multiple LED light sources at different frequencies. Each LED is modulated at a unique frequency (e.g., f1, f2, f3), creating periodic signals that can be simultaneously detected and later separated through demodulation. This transforms the sequential wavelength selection problem into a parallel periodic signal detection problem, enabling simultaneous measurement of multiple wavelengths.
2Measurement precision
If a tunable excitation source with lock-in detection is used, then multiple wavelengths can be detected, but the system becomes complex and simultaneous detection is not achieved
Solution Approach 1:
The patent merges multiple simple LED light sources into a single illumination system, each emitting at a different wavelength. Instead of using a complex tunable excitation source, multiple fixed-wavelength LEDs are combined and simultaneously activated. The Fabry-Perot interferometer acts as a wavelength-selective element that can be tuned to different wavelengths, allowing the system to maintain simplicity while achieving multi-wavelength detection capability.
Solution Approach 2:
The Fabry-Perot interferometer serves as an intermediary element between the multi-wavelength LED sources and the detector. It selectively transmits specific wavelength bands while blocking others, acting as a tunable wavelength filter. This intermediary allows the system to process multiple wavelengths simultaneously by adjusting the interferometer's transmission characteristics without requiring complex detection electronics for each wavelength.
3Measurement precision
If multiple individual detectors with their own interferometers are used, then each wavelength can be detected, but the device complexity increases
Solution Approach 1:
The patent makes a single detector universal by using it to detect all wavelength bands simultaneously. The Fabry-Perot interferometer is tuned to transmit different wavelength bands at different times or simultaneously at different spatial locations, and the single detector records all these signals. This multi-functional approach eliminates the need for multiple specialized detectors, significantly reducing system complexity while maintaining the ability to detect multiple wavelengths.
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 approach enables simple, cost-effective simultaneous detection of multiple wavelengths, enhancing applications in concentration, color, and fluorescence measurements, particularly in industrial and biological contexts, by allowing the scanning of desired wavelength ranges and adapting passbands for individual light sources.
Implementation Method 1
a Fabry-Perot filter of multiple order such that signals from multiple orders are processed simultaneously
Implementation Method 2
The surfaces of the plates facing each other are coated by dielectric or metallic layers forming mirrors
Implementation Method 3
modulated light sources formed by multiple single light sources having different wavelengths
Implementation Method 4
When each of the light sources is modulated at an individual frequency, it is possible to detect simultaneously several pass bands
Implementation Method 5
The length of the gap is made electrically adjustable by piezo actuators, which are positioned between one plate and the Fabry-Perot support structure
Data Source
Figure 1a~1b
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AI summary
The invention relates to a spectrometer for material analysis and to a control method for a spectrometer. The spectrometer includes a radiant source (140) formed by multiple single radiation sources (141) having different central wavelengths, for generating a measuring signal, a measurement object (100) containing a material to be analyzed, at least one electrically tunable Fabry-Perot filter (120, 220) for the band pass filtering the measuring signal by at least two pass bands, and a detector (300, 400) for detecting said filtered measuring signals received from the measurement object (100). In accordance with the invention the spectrometer has means (312) for modulating each of the single radiation sources (141) and correspondingly means (307, 309) for demodulating the detected signals such that the signal from each single radiation source can be distinguished from each other in the detector (300, 400), and the spectrometer has means for detecting (300, 400) and demodulating (306, 307) multiple pass bands simultaneously.