Fast infrared imaging spectroscopy technique (FIIST)

Acousto-optic tunable filters (AOTFs) can be used as spectral filters in multispectral imaging applications. Acousto-optic crystals diffract a single wavelength from a broadband light beam, depending on the applied radio frequency signal. However, experimental measurements show that the actual performance is far from the expected behavior. We present an experimental characterization of several commercial off-the-shelf AOTFs for the implementation of multispectral imaging instruments. The diffraction performance of three bare crystals is compared, while a fourth AOTF crystal is mounted on the optical path of a multispectral imager to evaluate its performance. The experiments show that the behavior of all the analyzed AOTFs differs from the theoretical expectations and presents uneven diffraction efficiency, a Gaussian dependency with the applied power, and a strong nonlinear relationship with the driving signal frequency. The different behavior of each AOTF in terms of all the analyzed parameters shows the necessity for an in-depth characterization of the AOTF performance once mounted on a multispectral imaging device if quantitative measurements are required. Finally, several recommendations for use are derived from these experimental results.

Improving heterogeneous classification accuracy based on the MDFAT and the combination feature information of multi-spectral transmission images

Chapter 5 - Hyperspectral imaging applications

We propose an ultra-thin multiband terahertz metamaterial absorber, whose thickness is only 3.8 μm. Simulation results show that we can get four narrow absorption peaks with near-perfect absorption in the 4.5 THz-6.0 THz frequency range. The resonance absorption mechanism is interpreted by the electromagnetic field energy distributions at resonance frequency. Moreover, we also analyze the sensing performances of the absorber in the refractive index and the thickness of the analyte. The refractive index and thickness sensitivities of the sensor are 0.471 THz/RIU, 0.4 THz/μm and the FOMs are 8.887RIU−1, 8.163 μm−1,respectively. The absorber has potential applications in photodetector, multi-spectral imaging and biosensors.

No quantitative computed tomography (CT) biomarker is actually sufficiently accurate to assess Crohn's disease (CD) lesion activity, with adequate precision to guide clinical decisions. To assess the available literature on the use of iodine concentration (IC), from multi-spectral CT acquisition, as a quantitative parameter able to distinguish healthy from affected bowel and assess CD bowel activity and heterogeneity of activity along the involved segments. A literature search was conducted to identify original research studies published up to February 2022. The inclusion criteria were original research papers (>10 human participants), English language publications, focus on dual-energy CT (DECT) of CD with iodine quantification (IQ) as an outcome measure. The exclusion criteria were animal-only studies, languages other than English, review articles, case reports, correspondence, and study populations <10 patients. Nine studies were included in this review; all of which showed a strong correlation between IC measurements and CD activity markers, such as CD activity index (CDAI), endoscopy findings and simple endoscopic score for Crohn's disease (SES-CD), and routine CT enterography (CTE) signs and histopathologic score. Statistically significant differences in IC were reported between affected bowel segments and healthy ones (higher P value was P < 0.001), normal segments and those with active inflammation (P < 0.0001) as well as between patients with active disease and those in remission (P < 0.001). The mean normalized IC at DECTE could be a reliable tool in assisting radiologists in the diagnosis, classification and grading of CD activity.

In this paper, we investigate the possibilities offered by the extension of the connected component trees (cc-trees) to multivariate images. We propose a general framework for image processing using the cc-tree based on the lattice theory and we discuss the possible applications depending on the properties of the underlying ordered set. This theoretical reflexion is illustrated by two applications in multispectral astronomical imaging: source separation and object detection.

This paper presents an experimental investigation of the application of multispectral imaging in dermatology. The focus areas of this work are as follows: a) the improving the color reproduction accuracy of skin lesions, b) exploring the spectral feature of skin disease using the multispectral color enhancement technique, and c) multispectral image analysis aiming at supporting quantitative diagnosis. The experiment focused on inflammatory and immunologic diseases; the color of skin lesions associated with these diseases is believed to be difficult to reproduce by conventional imaging devices. In view of this fact, we demonstrate the effectiveness of using spectral information for the color reproduction and quantitative analysis of skin disorders.

High-resolution digital mapping of soil organic carbon and soil total nitrogen using DEM derivatives, Sentinel-1 and Sentinel-2 data based on machine learning algorithms

We present results of field evaluations of computed tomography imaging spectrometer (CTIS) systems, using an adaptive optics (AO) compensated telescope, for applications in astronomical multispectral imaging and imaging spectroscopy in both visible (0.4 - 0.7 μm) and near infrared (1.2 - 2.1 μm) bands. We develop and analyze a convolution model for this hyperspectral imaging method which includes a convolution representation of the effects of the AO system. We use expectation maximization, with additional prior constraints derived from the physics of the instrumental, statistical and atmospheric effects inherent in such observations, to extract details of features in the hyperspectral images. Data for this study were obtained using the Advanced Electro-Optics System (AEOS) -- a facility of the Air Force Maui Space Surviellance System.

When an incident electromagnetic wave is properly coupled to a waveguide's leaky eigenmode by a subwavelength grating, a guided-mode resonance takes place. This phenomenon can manifest itself as sharp, high quality resonances in the reflection spectra. Since these resonances are highly sensitive to the device structural parameters (-grating thickness, period, and filling factor), a tunable resonance can be implemented if one or more of these parameters are suitably varied. In this paper, the micro-electro-mechanical system (MEMS) concept is applied for tuning the spectral response of resonant filters through mechanical microscale alteration of the grating profile. We provide numerical solutions based on exact electromagnetic models of MEMS-tuned resonance gratings designed with common materials. Computed results for an example tunable element with 6.0 μm period and 2.4 μm thickness show MEMS tuning of ~3.4 μm in the ~9-12 μm band with ~100 nm resonance linewidth. These elements are promising candidates for MWIR (3-8 μm) and LWIR (8-15 μm) multispectral imaging applications.

Electroporation and ultrasound induced sonoporation has been showed to induce plasmid DNA transfection to the mice tibialis cranialis muscle. It offers new prospects for gene therapy and cancer treatment. However, numerous experimental data are still needed to deliver the plausible explanation of the mechanisms governing DNA electro- or sono-transfection, as well as to provide the updates on transfection protocols for transfection efficiency increase. In this study we aimed to apply non-invasive optical diagnostic methods for the real time evaluation of GFP transfection levels at the reduced costs for experimental apparatus and animal consumption. Our experimental set-up allowed monitoring of GFP levels in live mice tibialis cranialis muscle and provided the parameters for DNA transfection efficiency determination.

A five-band multispectral(MIS)imaging system has been constructed and tested by the Hughes Research Laboratories. It has five boresighted sensors mounted on a scanning pedestal in a completely mobile and self-contained instrumentation trailer. The systems are .8μ passive, 1.06μ active/ranging, 10.6μ active, 8-12μ passive and 95 GHz (3.2 mm) active/ranging. The MIS operates in all weather conditions and produces registered, calibrated and digitized 12-bit raster scanned imagery. Designed as a sensor test bed for DARPA, the MIS is a versatile and adaptable system, which has potential use for a wide range of imaging and non-imaging applications. Field tests conducted in Culver City, California and Climax, Colorado will be discussed and the applicability of the MIS to the acquisition and analysis of more diverse scenes will be discussed.

A multispectral imaging system for automated inspection of wholesome and systemically diseased chickens was developed and demonstrated. The disease of septicemia was selected as the detection target because it is the most common chicken disease in US. From visible/near-infrared reflectance spectra of poultry carcasses, average CIELAB L*(lightness), a*(redness), and b*(yellowness) values were analyzed. The difference of lightness between wholesome and septicemic chickens was significant. The multispectral imaging system consisted of a backilluminated CCD camera and a spectrometer with four narrow-band interference filters for 488, 540, 580, and 610 nm wavelengths, respectively. The 16-bit multispectral images of chicken carcasses were collected for image processing and analysis. Image processing algorithms, including image registration, flat-field correction, image segmentation, region of interest identification, feature measurement, and symptom recognition, were developed to differentiate septicemic chickens from wholesome ones. The image from 610-nm wavelength was used to create a mask to extract chicken images from background. The average reflectance intensities at 488, 540, 580, and 610 nm from different parts of the carcass in the front side were calculated. Moreover, four normalization methods and four normalized differentiation methods between two wavelengths were also calculated for comparison. Decision tree was applied to generate thresholds for differentiation between wholesome and septicemic chickens. Images were collected at three time frames. The images from the first time frame were used to generate first thresholds that were tested by the images from the second time frames. Then, the images from the first and second time frames were used together to generate second thresholds. The first and second thresholds were tested by the images from the third time frame, respectively. The results showed that using average intensity at 580 nm from the region of interest, 98.6% of septicemic chickens and 96.3% of wholesome chickens could be differentiated from each other. More training data could help to generate more appropriate thresholds used at different time frames.

INO has been active in microbolometer and FPA technology development since the early 1990s. Microbolometer detectors based on VO2 films with TCR above 3% are typically fabricated. VOx films with TCR above 2% have been developed for applications where FPA temperature is not stabilized. INO is continuing its development of high fill factor pixels with sizes down to 25 micrometers and new macro- and micro-packaging technology. All fabrication is done on six inch wafers in INOs newly expanded clean room facility. INO currently offers as standard products 256x1 and 160x120 pixel FPAs with 52 micrometers pixel pitch. Both arrays have simple, robust, and versatile CMOS readout integrated circuits (ROICs) that may be accessed in self-scanning or random access mode, and reference detectors for on-chip coarse offset and temperature drift compensation. Single frame NETDs (f/1, 300 K, 8-12 micrometers ) are on the order of 150 - 250 mK and may be reduced by frame averaging. Prototyping boards have been developed for both arrays, and the 160x120 FPA has been integrated in a number of thermal cameras and instruments. In collaboration with its clients, INO has developed several FPAs for specific space and terrestrial applications. Custom ROICs fabricated in several different CMOS processes from multiple foundries have been used. A 512x3 pixel microbolometer FPA with 39 micrometers pitch is being developed for the European Space Agency. The array is designed for multi-spectral pushbroom imaging applications and features a novel ROIC with very low 1/f noise, pixel by pixel offset and drift compensation, variable integration time, and digital output. Its single frame NETD (f/1, 300 K, 8-12 micrometers ) is nominally 80 mK.

Data fusion technique can produce fused images with high spatial resolution and abundant spectral information. A new image fusion algorithm based on two-dimension PCA and Curvelet transform will be proposed according to image process models specialities in this paper. First of all, we performed 2DPCA on the MS image to get the 1st principle component (PC1); then we applied Curvelet transform in Pan Image and PC1; lastly decomposition coefficients obtained was processed according to certain rules to get fused coefficients, and afterwards, we performed inverse Curvelet transform on them to acquire fused sub-images. Then we performed inverse 2DPCA transform on the other components and the fused sub-images to get fused images. Experiments will be carried out via application of multispectral and panchromatic images, and it turns out that this new algorithm can improve spatial resolution greatly while maintaining spectral information.