Intermediate image free computed tomography imaging spectrometer

The multi-spectal or hyper-spectral imager provides three dimensional description for spatial and spectral intensity distribution of objective scenes and it can be a powerful tool for remote sensing in much application. There are several approaches to collection three dimensional data cube of image, and most of them require a scanning mechanism. Therefore those methods are difficult to record both spectral and spatial information of a dynamic scene such as a missile in flight, changing rapidly red tide, and so forth. Computed Tomography Imaging Spectrometer (CTIS) is a new branch application of computed tomography technology. The CTISs with different type configuration have been reported by a few of author. Two main types of CTISs are proposed. One is to use the two dimension gratings like Dammann gratings, the two 1-D gratings placed in orthogonal way, or three 1-D gratings separated by 60 degree. Due to its temporally and spatially non-scanning technique, this type is capable of capturing the flash events and can be used for instantaneous spectral imaging. The main problem of these CTISs is that the diffractive efficiencies are not only depended on the various wavelength but also on the different diffractive orders. That will effect the reconstruction algorithm and its results. These problems lead to reduce the signal to noise and dynamic range of spectral imaging system. The other is to take the approaches such as rotational spectro-tomography, or grating combined with a rotational direct-view prism. The advantages of these approaches are a)high throughput and b)easy to obtain more uniform data of different projection, but its disadvantage is obvious that the moving parts must be adopted. In our work, a principle and configuration of CTIS is indicated, and especially, a novel hybrid diffractive-refractive element is proposed, which is a combination of an array of optical prisms and one dimension holographic gratings. It can provide the uniformity of performance of projection data in different directions. As a result of high throughput and non-scanning parts, it can collect transient spectral imaging. Furthermore this grating is easily fabricated relatively. The capability enables it to be a prospect of applications in variety of application fields. This type of CTIS with the novel hybrid diffractive-refractive element is designed.

Imaging systems such as the Computed Tomographic Imaging Spectrometer (CTIS) are modeled by the matrix equation <b>g = Hf</b>, which is the discretized form of the general imaging integral equation.. The matrix <b>H</b> describes the contribution to each element of the image g from each element of the hyperspectral object cube f. The vector <b>g</b> is the image of the spatial/spectral projections of <b>f</b> on a focal plane array (FPA). The matrix <b>H</b> is enormous, sparse and rectangular. It is extremely difficult to discretize the integral operator to obtain the matrix operator <b>H</b>. Normally <b>H</b> is constructed empirically from a series of monochromatic calibration images, which is a time consuming process. However we have been able to synthetically construct <b>H</b> by numerically modeling how the optical and diffractive elements in the CTIS project monochromatic point source data onto the FPA. We can evaluate a CTIS system by solving the imaging equation for <b>f</b> using both the empirical and synthetic <b>H</b> from some test data <b>g</b>. Comparison between the two results provides a means to evaluate and improve CTIS system calibration procedures noting that the synthetic system matrix <b>H</b> represents a baseline ideal system.

Computed Tomography Imaging Spectrometer (CTIS) systems are snapshot hyperspectral imaging devices capable of capturing dense spectra of static as well as dynamic scenes. A three-dimensional hyperspectral cube is smeared across the spatial dimension via Diffractive Optical Element (DOE) and projected across multiple angles forming a two-dimensional compressed sensor image. In this paper we demonstrate material characterization and classification capability of a compact CTIS system leveraging spectral signatures. Then we propose an approach to simultaneously reconstruct and segment into regions corresponding to different materials hyperspectral images with enhanced spatial resolution from CTIS sensor measurements.

The Computed Tomography Imaging Spectrometer (CTIS) permits a snapshot acquisition of a hyperspectral cube, through the creation of an image of indirect measurements which is then traditionally used for reconstruction of the cube. This reconstruction step is time-consuming and only yields an approximation of the original cube. Following a compressed learning framework, we compare the performance of a classification task carried out on reconstructed cubes on one hand, directly on the raw images on the other. Regarding the latter case, we propose in particular the use of a new Convolutional Neural Network (CNN) architecture called CTIS-Net, whose architecture is tailored to benefit from the specific structure of CTIS images. Results show a sizable increase compared to classification with a standard architecture and compared to a conventional classification on the reconstructed cubes.

We have constructed a portable computed tomography imaging spectrometer (CTIS) based on a previous laboratory-bench version. This spectrometer features a computer-generated phase-only hologram as the dispersive element and collects spatial and spectral data from the diffracted orders. CTIS is capable of flash spectral imaging. Reconstruction of the image cube from raw data is achieved by computed-tomography techniques. Other improvements from the original design include a more modular design, an automated and more precise calibration technique, and the inclusion of constraints in the image cube reconstruction. Reconstruction results compare favorably with measurements by a fiber spectrometer. Keywords: Imaging spectrometry, computed tomography, flash spectral imaging.

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.

We have constructed a computed-tomography imaging spectrometer that uses a phase-only computer-generated hologram (CGH) array illuminator as the disperser. This imaging spectrometer collects multiplexed spatial and spectral data simultaneously and can be used for flash spectral imaging. The CGH disperser has been designed to maintain nearly equal spectral diffraction efficiency among a 5 x 5 array of diffraction orders and to minimize diffraction efficiency into higher orders. Reconstruction of the (x, y, lambda) image cube from the raw, two-dimensional data is achieved by computed-tomography techniques. The reconstructed image and spectral-signature data compare favorably with measurements by other spectrometric methods.

A computed tomographic imaging spectrometer (CTIS) is an instrument which can simultaneously obtain image spatial and spectral information without moving parts in a single focal plane array integration time. When this instrument is combined with a channeled spectropolarimeter, the instrument can also obtain complete Stokes polarization information at each resolution element. The combined instrument, called a computed tomographic imaging channeled spectropolarimeter (CTICS), has been developed in the visible wavelength region. This paper summarizes the CTICS design and results obtained from data acquired during field testing of the CTICS instrument.

Complex atmospheric environment seriously affect the quality of wireless of information transmission. In order to improve the wireless optical communication quality, and reduce the influence of attenuation, flicker, angle misalignment caused by atmospheric scattering, absorption, turbulence, beam expander, mismatch, atmospheric channel model is established while coding techniques for error control in wireless optical communication was researched into.The improvement result of error rate by error correction coding in different SNR situations was obtained. The results showed that the LDPC coding can significantly reduce the BER. For Gaussian channel, SNR can be reduced 8 dB when BER is 10-6; For wireless optical communication , LDPC codes can make the error rate reduced by 4-5 orders of magnitude.

A variety of four-mirror telescopes are described, all corrected for spherical aberration, coma, and astigmatism; all unobscured; and all with spherical surfaces. Performance is discussed with an afocal beam expander and a flat-field telescope as typical design examples.

Hyperspectral imaging is being extensively investigated owing to its promising future in critical applications such as medical diagnostics, sensing, and surveillance. However, current techniques are complex with multiple alignment-sensitive components and spatiospectral parameters predetermined by manufacturers. In this paper, we demonstrate an end-to-end snapshot hyperspectral imaging technique and build a physics-informed dual attention neural network with multimodal learning. By modeling the 3D spectral cube reconstruction procedure and solving that compressive-imaging inverse problem, the hyperspectral volume can be directly recovered from only one scene RGB image. Spectra features and camera spectral sensitivity are jointly leveraged to retrieve the multiplexed spatiospectral correlations and realize hyperspectral imaging. With the help of integrated attention mechanism, useful information supplied by disparate modal components is adaptively learned and aggregated to make our network flexible for variable imaging systems. Results show that the proposed method is ultra-faster than the traditional scanning method, and 3.4 times more precise than the existing hyperspectral imaging convolutional neural network. We provide theory for network design, demonstrate training process, and present experimental results with high accuracy. Without bulky benchtop setups and strict experimental limitations, this simple and effective method offers great potential for future spectral imaging applications such as pathological digital stain, computational imaging and virtual/augmented reality display, etc.

We report on the design, tolerancing, and laboratory breadboard of an imaging spectrometer for the Earth Science Decadal Survey Hyperspectral and Infrared Imager (HyspIRI) mission. The spectrometer is of the Offner type but with a much longer slit than typical designs, with 1600 resolvable spatial elements along the slit for a length of 48 mm. Two such spectrometers cover more than the required swath while maintaining high throughput and signal-to-noise thanks to the large pixel size (30 &mu;m), relatively high speed (F/2.8) and small number of reflections. We also demonstrate a method for measuring smile using a linear array, and use the method to prove the achievement of negligible smile of less than 2% of a pixel over the entire 48 mm slit. Thus we show that this high-heritage, all-spherical mirror design can serve the requirements of the HyspIRI mission.

Imaging systems using aspheric imaging lenses with complementary computation can deliver performance unobtainable in conventional imaging systems. These new imaging systems, termed Wavefront coded imaging systems, use specialized optics to capture a coded image of the scene. Decoding the intermediate image provides the "human-usable" image expected of an imaging system. Computation for the decoding step can be made completely transparent to the user with today's technology. Real-time Wavefront coded systems are feasible and cost-effective. This "computational imaging" technology can be adapted to solve a wide range of imaging problems. Solutions include the ability to provide focus-free imaging, to increase the field of view, to increase the depth of read, to correct for aberrations (even in single lens systems), and to account for assembly and temperature induced misalignment. Wavefront coded imaging has been demonstrated across a wide range of applications, including microscopy, miniature cameras, machine vision systems, infrared imaging systems and telescopes.

Розглянуто оптичні параметри кругових мікропризмових заломлюючих пристроїв, які створені з двох ідентичних концентраторів світлових потоків із заданими граничними кутами заломлення променів. Виконано моделювання індикатриси променів для двохелементних рефракційних елементів. Розраховано параметри зменшення світлопропускання лінійних двохелементних пристроїв, які використовуються в офтальмології для визначення кута рефракції променів.

Laboratory-scale gaseous plasma events offer a rich environment for the study of ionization, energy transfer, and non-equilibrium dynamics, whose understanding plays a critical role in wakefield accelerators, inertial confinement fusion, and plasma ignition devices. Probing these dynamics, however, has been historically difficult due to their weak absorption of visible light and inherently challenging spatial and temporal scales. Recent advances in computational imaging have opened the door for advanced forms of plasma diagnostics with techniques such as single-shot ptychography (SSP); however, fidelity challenges and reduced resolution have limited the application of SSP to non-repeatable plasma dynamics. Here we introduce a near-field implementation of SSP that delivers enhanced fidelity and resolution, as well as improved robustness to noise compared to far-field methods, verified through systematic experimental and numerical comparisons. Using this method, we demonstrate ptychographic imaging of non-repeatable plasma dynamics through the analysis of a full temporal trace of an electrostatic discharge event. These results establish near-field SSP as a powerful plasma diagnostic tool, opening the pathway toward 3D, hyperspectral, and single-shot ultrafast motion-picture ptychographic imaging of complex plasma systems.