Spectrally resolved insect flashes by sunlight

Sammanfattning

Insects are vital for the environment and biodiversity. Optics-based remote techniques can quickly and effectively identify and track insects in their natural habitat. This has the potential to speed up and improve the time-consuming process of manually monitoring insect diversity. This thesis presents a method to remotely sense insects by analyzing the sunlight reflected by free-flying insects. The study proposes a novel approach by simultaneously capturing the spectral and temporal signals of reflected sunlight, containing new information about the spectral properties of insects in the visible wavelength range. For this project, a spectrometer is designed using raytracing, CAD-design, and 3D-printing. The instrument is capable of analyzing light in the visible to near-infrared range (420-840 nm) with 32 spectral bands. The instrument was calibrated and successfully deployed in the field to capture sunlight flashes from free-flying insects, with a sampling rate of 20 kHz. The collected data shows that the instrument successfully captured signals from insects. This data is used to determine if spectrally resolved modulation provides additional information for species differentiation. To achieve this, a hierarchical clustering algorithm is applied to both the spectrally resolved and non-spectrally resolved signals. The number of clusters found when using both spectral and temporal data was larger than the number of clusters found when using only temporal data. The conclusion is drawn that there is additional information for species identification in the spectral data.