Surveying disease vectors is currently excessively laborious for continuous and widespread monitoring. Wing beat modulation spectroscopy gives opportunity for species and sex recognition in electronic traps or mosquito target classification in lidar. We used a polarimetric dual-wavelength-band laboratory system to record kHz modulated backscattered light from insects. The system operates in the near and short-wave infrared at 808 nm and 1550 nm and retrieves both co- and depolarized light. Here we give clues on the harmonic content and covariance of four mosquito species and fruit flies. Further, we interpret the interdependence of harmonic strengths when insects transit the probe volume with random heading direction and provide correlation matrices for coherent and incoherent light. Using the obtained parameters, we demonstrate that species that are difficult to distinguish with microscope can be classified with high accuracy. The results are valuable for understanding wingbeat harmonics in relation to heading and valuable for optimal sensor design for disease vector surveillance.
The recent several years we developed the Scheimpflug lidar method. We combined an invention from the 19th century
with modern optoelectronics such as diode lasers and CMOS array from the 21st century. The approach exceeds
expectations of background suppression, sensitivity and resolution beyond known from time-of-flight lidars. We
accomplished multiband elastic atmospheric lidars for resolving single particles and aerosol plumes from 405 nm to 1550
nm. We pursued hyperspectral differential absorption lidar for molecular species. We demonstrated a simple method of
inelastic hyperspectral lidar for profiling aquatic environments and vegetation structure. Not least, we have developed
polarimetric Scheimpflug lidar with multi-kHz sampling rates for remote modulation spectroscopy and classification of
aerofauna. All these advances are thanks to the Scheimpflug principle. Here we give a review of how far we have come
and shed light on the limitations and opportunities for future directions. In particular, we show how the biosphere can be
resolved with unsurpassed resolution in space and time, and share our expectation on how this can revolutionize
ecological analysis and management in relation to agricultural pests, disease vectors and pollinator problematics.
The migration of aerofauna is a seasonal phenomenon of global scale, engaging billions of individuals in long-distance movements every year. Multiband lidar systems are commonly employed for the monitoring of aerosols and atmospheric gases, and a number of systems are operated regularly across Europe in the framework of the European Aerosol Lidar Network (EARLINET). This work examines the feasibility of utilizing EARLINET for the monitoring and classification of migratory fauna based on their pigmentation. An EARLINET Raman lidar system in Athens transmits laser pulses in three bands. By installing a four-channel digital oscilloscope on the system, the backscattered light from single-laser shots is measured. Roughly 100 h of data were gathered in the summer of 2013. The data were examined for aerofauna observations, and a total of 1735 observations interpreted as airborne organisms intercepting the laser beam were found during the study period in July to August 2013. The properties of the observations were analyzed spectrally and intercompared. A spectral multimodality that could be related to different observed species is shown. The system used in this pilot study is located in Athens, Greece. It is concluded that monitoring aerial migration using it and other similar systems is feasible with minor modifications, and that in-flight species classification could be possible.
A kHz optical remote sensing system is implemented to determine insect melanization features. This is done by measuring the backscatter signal in the visible and near-infrared (VIS-NIR) and short-wave infrared (SWIR) in situ. It is shown that backscatter cross section in the SWIR is insensitive to melanization and absolute melanization can be derived from the ratio of backscatter cross section of different bands (SWIR/VIS-NIR). We have shown that reflectance from insect is stronger in the SWIR as compared to NIR and VIS. This reveals that melanization plays a big role to determine backscatter cross section. One can use this feature as a tool to improve insect species and age classification. To support the findings, we illustrated melanization feature using three different insects [dead, dried specimens of snow white moth (Spilosoma genus), fox moth (Macrothylacia), and leather beetle (Odontotaenius genus)]. It is shown that reflectance from the leather beetle in the VIS and NIR is more affected by melanization as compared with snow white moth.
kHz optical remote sensing system is implemented to determine melanization and backscatter cross-section in the near infrared (NIR) and shortwave infrared (SWIR) in situ. It is shown that backscatter cross-section in the SWIR is insensitive to melanization and absolute melanization can be derived from the ratio of backscatter cross-section in two bands (SWIR/NIR). We have shown that insects reflect more strongly in the SWIR as compared to NIR and Visible (VIS) in accordance with previous findings. This is illustrated using three different insects (Snow white moth (spilosoma genus), Fox moth (Macrothylacia) and Leather beetle (Odontotaenius genus)) and it is shown that the reflectance of the Leather beetle in the VIS and NIR is more affected by melanization as compared with snow white moth.
Quantitative investigation of insect activity in their natural habitat is a challenging task for entomologists. It is difficult to address questions such as flight direction, predation strength, and overall activities using the current techniques such as traps and sweep nets. A multispectral kHz remote detection system using sunlight as an illumination source is presented. We explore the possibilities of remote optical classification of insects based on their wing-beat frequencies and iridescence features. It is shown that the wing-beat frequency of the fast insect events can be resolved by implementing high-sampling frequency. The iridescence features generated from the change of color in two channels (visible and near-infrared) during wing-beat cycle are presented. We show that the shape of the wing-beat trajectory is different for different insects. The flight direction of an atmospheric insect is also determined using a silicon quadrant detector.
Quantitative investigation of insect activity in their natural habitat is a challenging task for entomologist. It is difficult to address questions such as flight direction, predation strength and overall activities using the current techniques such as traps and sweep nets. A multi-spectral kHz remote detection system using sunlight as an illumination source is presented. We explore possibilities of remote optical classification of insects based on their wing-beat frequencies and iridescence features. It is shown that the wing-beat frequency of the fast insect events can be resolved by implementing high sampling frequency. The iridescence features generated from the change of color in two channels (visible and near infrared) during wing-beat cycle is presented. We show that the shape of the wing-beat trajectory is different for different insects. The flight direction of atmospheric insect is also determined using silicon quadrant detector.
Optical techniques for tissue diagnostics currently are experiencing tremendous growth in biomedical applications, mainly due to their noninvasive, inexpensive, and real-time functionality. Here, we demonstrate a hand-held fiber optic probe instrument based on fluorescence/reflectance spectroscopy for precise tumor delineation. It is mainly aimed for brain tumor resection guidance with clinical adaptation to minimize the disruption of the standard surgical workflow and is meant as a complement to the state-of-the-art fluorescence surgical microscopy technique. Multiple light sources with fast pulse modulation and detection enable precise quantification of protoporphyrin IX (PpIX), tissue optical properties, and ambient light suppression. Laboratory measurements show the system is insensitive to strong ambient light. Validation measurements of tissue phantoms using nonlinear least squares support vector machines (LS-SVM) regression analysis demonstrate an error of <5% for PpIX concentration ranging from 400 to 1000 nM, even in the presence of large variations in phantom optical properties. The mean error is 3% for reduced scattering coefficient and 5% for blood concentration. Diagnostic precision of 100% was obtained by LS-SVM classification for in vivo skin tumors with topically applied 5-aminolevulinic acid during photodynamic therapy. The probe could easily be generalized to other tissue types and fluorophores for therapy guidance and monitoring.
Total resection of glioblastoma multiform (GBM), the most common and aggressive malignant brain tumor, is challenging among other things due to difficulty in intraoperative discrimination between normal and residual tumor cells. This project demonstrates the potential of a system based on a combination of autofluorescence and diffuse reflectance spectroscopy to be useful as an intraoperative guiding tool. In this context, a system based on 5 LEDs coupled to optical fibers was employed to deliver UV/visible light to the sample sequentially. Remitted light from the tissue; including diffuse reflected and fluorescence of endogenous and exogenous fluorophores, as well as its photobleaching product, is transmitted to one photodiode and four avalanche photodiodes. This instrument has been evaluated with very promising results by performing various tissue-equivalent phantom laboratory and clinical studies on skin lesions.
Glioblastoma multiforme (GBM) has long been known as the most common and aggressive form of brain malignancy. The morphological similarities of the malignant and surrounding tissue cause difficulties to distinct the tumors during surgery. In order to achieve better results in resecting malignant brain tumors, a fiber based optical system which can be used intraoperative is developed in this project. In this context, the system hardware details, system controlling interfaces and laboratory testing results are presented. Based on the results obtained from various tests with tissue-equivalent phantoms, the system is proved to have stable performance, robust structure, and have good linearity as well as high sensitivity to low PpIX concentration under strong ambient light conditions.
We report an accurate optical differentiation technique between healthy and malaria-infected erythrocytes by quasi-simultaneous measurements of transmittance, reflectance, and scattering properties of unstained blood smears using a multispectral and multimode light-emitting diode microscope. We propose a technique for automated imaging, identification, and counting of malaria-infected erythrocytes for real-time and cost-effective parasitaemia diagnosis as an effective alternative to the manual screening of stained blood smears, now considered to be the gold standard in malaria diagnosis. We evaluate the performance of our algorithm against manual estimations of an expert and show a spectrally resolved increased scattering from malaria-infected blood cells.
We present a method based on passive spectroscopy with aim to remotely study flying birds. A compact spectrometer is
continuously recording spectra of a small section of the sky, waiting for birds to obscure part of the field-of-view when
they pass the field in flight. In such situations the total light intensity received through the telescope, looking straight up,
will change very rapidly as compared to the otherwise slowly varying sky light. On passage of a bird, both the total
intensity and the spectral shape of the captured light changes notably. A camera aimed in the same direction as the
telescope, although with a wider field-of-view, is triggered by the sudden intensity changes in the spectrometer to record
additional information, which may be used for studies of migration and orientation. Example results from a trial are
presented and discussed. The study is meant to explore the information that could be gathered and extracted with the help
of a spectrometer connected to a telescope. Information regarding the color, size and height of flying birds is discussed.
Specifically, an application for passive distance determination utilizing the atmospheric oxygen A-band absorption at
around 760 nm is discussed.
We present the application of two fibre-optic-coupled time-resolved spectrofluorometers and a compact steady-state
diffuse reflected light/fluorescence spectrometer to in vivo and ex vivo studies of skin cancer and osteoarthritis. In a
clinical study of skin cancer, 27 lesions on 25 patients were investigated in vivo before surgical excision of the region
measured. Preliminary analysis reveals a statistically significant decrease in the autofluorescence lifetime of basal cell
carcinomas compared to neighbouring healthy tissue. A study of autofluorescence signals associated with the onset of
osteoarthritis indicates autofluorescence lifetime changes associated with collagen degradation.
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