Multiplexed Excitation Emission Matrix Spectroscopy Using Spatial Light Modulators
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Solution Overview
Problem
Current fluorescence excitation emission matrix (EEM) spectroscopy techniques are inefficient due to the mechanical movement of gratings, which limits the use of light and requires extensive time to generate spectra, and existing multiplexing methods are prone to interference from harmonics.
Innovation Solution
The use of frequency division multiplexing or orthogonal frequency division multiplexing, combined with spatial light modulators or digital micromirror arrays, to encode and decode excitation and emission light, allowing for simultaneous data collection and reducing the need for mechanical movement, while employing Hadamard transforms to overcome harmonic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pivoting grating is used to scan excitation wavelengths, then spectral resolution is improved, but data acquisition time increases significantly and light utilization efficiency decreases
Solution Approach 1:
The excitation spectrum is segmented into multiple wavelength bands, with each band assigned to a separate detector element. This allows simultaneous detection of multiple wavelength regions without mechanical scanning, resolving the contradiction between spectral resolution and data acquisition time.
Solution Approach 2:
The patent transitions from one-dimensional sequential wavelength scanning to two-dimensional parallel detection by spatially dispersing different excitation wavelengths across multiple detector elements. This dimensional change enables simultaneous measurement of multiple wavelengths, eliminating the time penalty of mechanical scanning while maintaining spectral resolution.
2Measurement precision
If a pivoting grating is used to scan excitation wavelengths, then spectral resolution is improved, but light utilization efficiency decreases
Solution Approach 1:
The excitation spectrum is segmented into multiple wavelength bands, with each band assigned to a separate detector element. This allows simultaneous detection of multiple wavelength regions without mechanical scanning, resolving the contradiction between spectral resolution and data acquisition time.
Solution Approach 2:
The patent implements continuous illumination of the sample with the full excitation spectrum simultaneously, rather than sequentially scanning through wavelengths. This continuous parallel action maximizes light utilization efficiency while maintaining spectral resolution through spatial dispersion and multi-element detection.
3Productivity
If Fourier transform demodulation is used to decode multiplexed signals, then data acquisition speed is improved, but harmonic interference increases
Solution Approach 1:
The patent extracts and eliminates the harmonic interference problem by abandoning Fourier transform demodulation in favor of direct spatial encoding. Instead of using time-domain modulation that generates harmonics, the system uses spatial domain encoding where each wavelength is directly mapped to a specific detector element, removing the source of harmonic interference while maintaining high data acquisition speed.
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 significantly increases the efficiency of EEM spectroscopy by utilizing the entire light spectrum and reducing data acquisition time, achieving high-sensitivity and rapid acquisition of 2D spectra with minimal user input and reduced cross-talk.
Implementation Method 1
If each excitation wavelength is individually modulated with a unique frequency, the entire spectrum of the light source can be used to excite the sample and all the emission collected simultaneously
Implementation Method 2
The spectrum can then be obtained through demodulation of the resultant signal, for example by using a Fourier transform
Implementation Method 3
Fluorescence spectroscopy is a highly sensitive, nearly background-free technique for chemical detection
Data Source
AI summary
Described herein is an excitation emission matrix (EEM) spectrometer and method, comprising a multiplexer that encodes excitation light produced by at least one excitation light source; and a demultiplexer that decodes encoded light emitted from a sample, and produces an output indicative of a characteristic of the sample. Embodiments are described wherein the multiplexer and the demultiplexer may comprise FDM or OFDM, and wherein both the excitation light and the emitted light may be encoded using a DMA or a SLM. In some embodiments the same DMA or SLM may be used to encode the excitation light and the emitted light. In some embodiments excitation light may be encoded using a Walsh function, or the excitation light may be encoded using a Walsh function and the emitted light may be decoded using an inverse Hadamard transformation.