Quasi-3D Fluorescence Spectroscopy for Rapid On-Site Algae Species Analysis

This paper presents a novel quasi-three-dimensional (quasi-3D) Fluorescence Spectroscopy technique for rapid and on-site algae species classification. By integrating multi-wavelength excitation with a software lock-in amplifier (SLIA) system, the method achieves high signal-to-noise ratio (SNR) and robust fluorescence detection under complex ambient light conditions. Experimental results show that the SNR improved from –9.54 dB to 14.11 dB at 10 meters, and up to 26.43 dB at 5 meters. Using four excitation wavelengths (405, 465, 520, and 638 nm), fluorescence spectra were collected from four representative microalgae species, yielding a dataset of 4,812 samples. Dimensionality reduction via Principal Component Analysis (PCA) and classification using a lightweight SVM model resulted in 100% test accuracy. Compared to conventional 3D or discrete spectral methods, the proposed system significantly reduces acquisition time to within 10 seconds while retaining critical spectral information. The technique shows strong potential for field-deployable applications such as harmful algal bloom detection, aquatic ecosystem monitoring, and real-time environmental sensing. Future work will focus on expanding species coverage and validating performance under dynamic environmental conditions.