Multi-spectral camera set-ups may generally allow for creating surveillance applications even under unfavorable conditions, such as low-light environments or scenes involving vastly different lighting conditions. A high- resolution color camera, a high-dynamic-range camera and an infrared thermal camera were combined into a self-sufficient platform for continuous outdoor operation. The sheer amount of produced data poses a serious challenge, both in terms of available bandwidth and processing power, because self-sufficiency requires using relatively low-power components, and privacy, as high-resolution, multi-spectral image data are sensitive information. Thus, relevant objects of interest had to be efficiently extracted, tracked and georeferenced on the sensor platform. These data, from one or more sensorheads, are then sent via WLAN or mobile data link to a central control unit, possibly anonymized, e.g. prompting immediate action by a human operator in a disaster response use case, or stored for further offline analysis when used in the framework of "Smart City". Applying the classic stereo vision approach would require calibrating both intrinsic and extrinsic parameters of all cameras. The input data's multi-spectral nature complicates the correspondence problem for extrinsic parameter calibration and subsequent stereo matching, while intrinsic parameter calibration according to the pinhole camera model is made difficult due to the cameras having to be focused at infinity. However, by making certain reasonable assumptions about the observed scene in typical use cases, accepting a possible loss in localization accuracy, camera calibration could be limited to the bare minimum and less computational power was required at run-time.
To evaluated capabilities of multispectral TD-DOT systems in reflection geometry, we performed a measurement campaign on multimaterial composition phantoms. Results show correct composition gradation of inclusions but still lack absolute accuracy.
This work presents the proof of concept of the detection of global and surface optical index variations by surface plasmon resonance (SPR) thanks to optical fiber bundles. This work is the first necessary step for the future design of a lab-on-fiber tool dedicated to molecular analysis for endoscopic diagnosis. Our approach is based on nanostructured optical fiber bundles comprising several thousands of individual optical fibers. These nanostructures were coated by a thin gold layer in order to gain interesting optical properties such like SPR. The sensitivity and resolution of the bundle to global optical index changes were measured in retro-reflection. We performed numerical simulations in order to optimize the fiber tip geometry, gold coating thickness and finally enhance their analytical performances. We achieved a resolution of 10-4 refractive index unit, which is fully compatible with the detection of biological interactions involving large proteins or bacteria. Finally, we proved that our sensor was sensitive to surface optical index variations and able to detect the adsorption of a thin self-assembled molecular layer.
Multicomponent phantom measurements are carried out to evaluate the ability of multispectral time domain diffuse optical tomography in reflectance geometry to quantify the position and the composition of small heterogeneities at depths of 1-1.5 cm in turbid media. Time-resolved data were analyzed with the Mellin-Laplace transform. Results show good localization and correct composition gradation of objects but still a lack of absolute material composition accuracy when no a priori geometry information is known.
This contribution presents a fast global adjustment scheme exploiting SURF descriptor locations for constructing large skin mosaics. Precision in pairwise image registration is well-preserved while significantly reducing the global mosaicing error.
In many Asian countries, motorcyclists have a higher fatality rate as compared to other vehicles. Among many other factors, rear end collisions are also contributing for these fatalities. Collision detection systems can be useful to minimize these accidents. However, the designing of efficient and cost effective collision detection system for motorcyclist is still a major challenge. In this paper, an acoustic information based, cost effective and efficient collision detection system is proposed for motorcycle applications. The proposed technique uses the Short time Fourier Transform (STFT) to extract the features from the audio signal and Principal component analysis (PCA) has been used to reduce the feature vector length. The reduction of feature length, further increases the performance of this technique. The proposed technique has been tested on self recorded dataset and gives accuracy of 97.87%. We believe that this method can help to reduce a significant number of motorcycle accidents.
We present a new experimental technique based on the analysis of beam self-action to measure optical nonlinearity in planar waveguides. This technique is applied to analyze the nonlinear properties of slab chalcogenide waveguides that can develop Kerr induced self-focusing or self-defocusing, depending upon the waveguide structure and composition. Optical nonlinearity in chalcogenide waveguide is studied in the 1200 nm to 1550 nm wavelength range in femtosecond regime. Results of the proposed technique compare favorably with n(2) values obtained with the Z-scan technique. In addition, beam self-trapping in the chalcogenide waveguides due to material photosensitivity is also observed.
Infrared laser light radiation can be used to depolarize neurons and to stimulate neural activity. The absorption of infrared radiation and heating of biological tissue is thought to be the underlying mechanism of this phenomenon whereby local temperature increases in the plasma membrane of cells either directly influence membrane properties or act via temperature sensitive ion channels. Action potentials are typically measured electrically in neurons with microelectrodes, but they can also be observed using fluorescence microscopy techniques that use synthetic or genetically encoded calcium indicators. In this work, we studied the impact of infrared laser light on neuronal calcium signals to address the mechanism of these thermal effects. Cultured primary mouse hippocampal neurons expressing the genetically encoded calcium indicator GCaMP6s were used in combination with the temperature sensitive fluorophore Rhodamine B to measure calcium signals and temperature changes at the cellular level. Here we present our all-optical strategy for studying the influence of infrared laser light on neuronal activity.
In this work, we propose an alternative to the sub-sampling limitation in the single-waveguide configuration of SWIFTS technology using the electro-optical properties of Lithium Niobate (LiNbO3) technology. A Mach-Zehnder intensity modulator, with an initial imbalance between the arms, is coupled with a linear SWIFTS-Lippmann spectrometer. With quite reasonable control voltages (< 100V), "dynamic" wide band fringes (generated by the unbalanced interferometer) can be moved under the nanodots to compensate the sub-sampling related to their spacing and rebuild the interferogram with a good sampling in a very short time, thanks to the electro-optical performances of Lithium Niobate technology. We present the measurements of broadband sources' interferograms sampled by this setup, and the considerations for spectral reconstructions for a SLED source at lambda = 850 nm.The study leads to a better understanding of the behavior of the spectrometer with model and local measurement of the cross-talk phenomenon between nanodots and pixels, photometries and efficiencies of diffusion.This work opens the way to electro-optic devices where external optical path delay scan could be replaced by internal phase-modulation using electro-optic effect.
We map out the group delays of all the 169 single-mode cores of a 30 cm long multi-core fiber using phase-shifting spectral interferometry. We then present and apply a new experimental concept suitable for partially compensating the measured inter-core group delay dispersion. The compensation scheme is based on two wave front shapers in a 4-f geometry and group delays are imposed in the Fourier plane between them. These results are of relevance for cases where one desires to perform imaging through optical fibers using femtosecond excitation as is the case in the two-photon lensless endoscopes which have recently been demonstrated.
High dynamic range (HDR) displays use local backlight modulation to produce both high brightness levels and large contrast ratios. Thus, the display rendering algorithm and its parameters may greatly affect HDR visual experience. In this paper, we analyze the impact of display rendering on perceived quality for a specific display (SIM2 HDR47) and for a popular application scenario, i.e., HDR image compression. To this end, we assess whether significant differences exist between subjective quality of compressed images, when these are displayed using either the built-in rendering of the display, or a rendering algorithm developed by ourselves. As a second contribution of this paper, we investigate whether the possibility to estimate the true pixel-wise luminance emitted by the display, offered by our rendering approach, can improve the performance of HDR objective quality metrics that require true pixel-wise luminance as input.
Scratches at the surface of fused silica optics can be detrimental for the performance of optical systems because they initiate damage on the optic but also they perturb the amplitude or phase of the transmitted laser light. Removing scratches by conventional polishing techniques can be time consuming as it is an iterative and long process, especially when hours of polishing time are required to obtain very high surface accuracy. So we have investigated ways to remove them with local laser processing. The silica is then heated at temperature higher than the softening point to heal the cracks.
We report an investigation on optoelectronic oscillators based on a combination of a fiber delay line and a whispering gallery mode resonator. We analyze the dynamical processes which are key for the understanding of the spectral purity of these oscillators. We therefore show how combining both optical elements leads to significant improvement of the spectral purity of the oscillator, as it leads to a spurious rejection rate higher than 50 dB.
Corrosion in marine environment is a complex dynamic process influenced mainly by physical chemical, microbiological and mechanical parameters. Times for maintenance related to corrosion are greater than 80% of the total repair. Reducing this cost would be a significant saving, and an effective treatment can reduce times related to ships repairing. Biofouling is a main cause of corrosion and its formation contains four steps.To inhibit biofouling it is proposed a treatment based on non-thermal plasma produced by GlidArc, which can be applied before the immersion of small boats in the sea, as well as cleaning treatment of the hull after a period of time. This work presents the microbiological results of treatment of metal surfaces (naval OL36 steel) with GlidArc technology, according to the first, respectively the second phase formation of biofouling. Samples of naval steel were prepared with three specific naval paints and before the treatment have been introduced in seawater.Microbiological results have been compared for two types of treatments based on GlidArc. In the first case the painted samples are submitted to direct action of non-thermal plasma. In the second case the plasma produced by GlidArc technology is used to activate a solution (plasma activated water = PAW) and then the samples are introduced into this water.
When an alt-azimuth telescope is tracking at a specific field, it is necessary to use a de-rotator system to compensate the Earth's rotation of the field of view. In order, to keep the telescope tracking the field of view selected, the instrument will need to a rotation system for compensating it [1]. The new WEAVE [2] two degrees field of view requires a new field de-rotator on the top-end of the telescope. The rotator system has been designed with a direct drive motor which eliminates the need for mechanical transmission elements such as gearboxes, speed reducers, and worm gear drives. This design is a huge advantage for the system performance and lifetime because it eliminates undesirable characteristics such as long-time drift, elasticity, and backlash. The hardware control system has been developed with a Rockwell servo-drive and controller. The rotator has to be controlled by the high-level software which is also responsible for the telescope control. This paper summarizes the model developed for simulating and the software which will be used to accept the rotator system. A performance study is also carried out to test the CIP (Common Industrial Protocol) for communications between the high-level software and the rotator hardware.
