Method for coupling modulatedscattered light from free flyinginsects to harmonics and theirrelative phases

Abstract: Using laser it is possible to measure the backscattered light from insects. The resulting signal can then be analysed in order to potentially determine the species of the insect. Estimating the fundamental wing beat frequency (FWBF) of insects is important in order do this classification of species, which is an area of research that has been explored previously. In this thesis, the relative phase of the FWBF and its overtones are analyzed with the matched phase reassignment (MPR) method. The frequencies are estimated with the matched reassignment (MR) method. The results of the phase estimations are dependent on variables such as the FWBF, noise levels and number of overtones. Furthermore, the results from the frequency estimation affects the outcome of the phase estimation to a large extent, making the phase estimations vulnerable to wrongly classified frequencies. In order to obtain real data an test chamber setup was built with the purpose of producing modulated scattered light from free flying insects. The setup used two continuous-wave lasers with the wavelengths 808 nm and 1320 nm. The setup also used a camera to allow a 3D reconstruction of the recorded insects flight path. This setup worked as intended and recorded data was obtained from fruit flies (drosophila melanogaster). It can be concluded that the phase estimations work well for data with low amounts of noise and for FWBFs. Higher levels of noise corrupt the signal too much for the MPR method to work as intended. The same goes for higher FWBFs where the results are not as good on lower frequencies. This, however, is because of the frequencies being wrongly estimated which in turn leads to incorrect phases.