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上海必和 Advances in-hyperspectral_imaging_3-08超光谱高光谱多光谱
上海必和 Advances in-hyperspectral_imaging_3-08超光谱高光谱多光谱
上海必和 Advances in-hyperspectral_imaging_3-08超光谱高光谱多光谱
上海必和 Advances in-hyperspectral_imaging_3-08超光谱高光谱多光谱
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上海必和 Advances in-hyperspectral_imaging_3-08超光谱高光谱多光谱


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  1. March, 2008 Advances in Hyperspectral Imaging Authors: Jay Zakrzewski, Jay Julian (Headwall Photonics) Abstract: Capturing precise spectral information from process manufacturing applications has traditionally involved in-line or at-line single point spectral detection instrumentation which sample a very small area of the overall product. Often, multiple sensors are necessary to cover a required spatial area, otherwise a time consuming routine of many single measurements are necessary to spatially map the area of interest. These options are costly due to redundant equipment, calibration concerns, and time. Headwall Photonics will present several Hyperspectral sensor configurations which provide precise spectral data of small spatial features viewed through a lens “push-broom” technique, or via a multi-channel fiber optic collection at discrete measurement points simultaneously. Optimal imaging performance is obtained using an imaging spectrometer design based on an all reflective, concentric f/2 spectrometer utilizing aberration-corrected optics. In order to minimize stray light, the imaging spectrometer utilizes no prism or transmissive optics. Discussion: Hyperspectral imaging is a technique used to ascertain wavelength intensity mapping of a scene with high spatial resolution. This blend of spectral data and spatial imagery can be analyzed for color, chemical identification, material homogeneity and many other spectrophotometric measurements. The spectral imaging accuracy of these systems also enables simultaneous spectral data collection of large volumes of discrete optical fibers, each collecting spectra from unique locations. Highly resolved spatial imaging performance combined with high spectral resolution over a broad spectral bandwidth is proving to be valuable in tissue scanning, cancer detection, micro-well plate screening, biomedical microscopy applications, nano particle research, hazardous materials detection, as well as many other spectral sensing applications Flexibility in design of advanced spectral imaging systems also allows trade off between spatial height and spectral bandwidth dispersion, enabling either very high spectral resolution, or very large spatial field of view. In general, today’s applications involve reflection, absorption, fluorescence, and Raman spectroscopy. The Headwall Photonics Hyperspec™ is most often employed as a scanning push-broom imager. For each moment in time, or camera fram capture, a Field of View (FOV) observed by the objective lens is imaged onto a tall slit aperture. The scene which fills the slit aperture is re-imaged through the patented aberration corrected spectrometer with the wavelengths dispersed by a grating onto a 2D Focal Plane Array (FPA) camera such as a CCD. One axis of the FPA (pixel-rows) corresponds to the imaged spatial positions along the slit height in a 1:1 relationship. The second axis (spectral; pixel columns) corresponds to spectral wavelength, which is linearly dispersed and calibrated. Each 2D image (frame capture), is digitized by the FPA into a 2D data-array corresponding to the field of view imaged through the slit. While scanning a wide scene, such as a human tissue sample, multiple 2D image frame captures are taken while spatially stepping across the desired scene width, and these individual frames are stacked like a deck of cards to produce a data file commonly called a Hyper-cube. Each pixels value within this image Hyper-cube represents the spectral intensity plot of that pixels small field of view on the scene. Figure 1 is a graphical representation of a Hypercube.
  2. Headwall Photonics, Inc. Figure 1: Hyperspectral Cube (Source: AVIRIS Image Cube) The resultant three dimensional matrix of data can be analyzed wholly, or interrogated in several ways such as: 1. Vector: spectra at a position X, Y 2. Vector: X-profile at a particular wavelength 3. Vector: Y-profile at a particular wavelength 4. 2D Field: X, Y intensities at a particular wavelength (like a notch-filtered image of any wavelength) 5. Processed into pseudo-color rendered pictures identifying regions where the intensities of a certain wavelength fall within prescribed parameters 6. Processed into pseudo-color rendered pictures identifying regions where a certain spectral signature (spectral-waveform) fall within prescribed parameters The following diagram (Figure 2) provides an example of the scanning approach in Push-broom scanning. Figure 2. Push-broom scanning parameters
  3. Headwall Photonics, Inc. The original holographic corrected grating installed in each Headwall Hyperspectral Imager is fabricated using the same materials and process as Telcordia GR1221 telecommunications gratings validated for the damp-heat, hi-temperature, and temperature cycling tests. The Hyperspec has been employed in several demanding field applications. In addition to several proprietary industrial applications are the following examples of military, research, and space qualified aerospace deployments: • Hyperspec VS10 – Marine Optical Buoy (MOBY) Project; measurement of upwelling radiance and downwelling irradiance at the sea surface and at three deeper depths; deployed by US National Oceanic and Atmospheric Administration (NOAA); with initial deployment in 1993, this instrument is responsible for calibration input of most of the US and international weather satellites for forecasting conditions from El Niño weather patterns (paper available) • Hyperspec VS30 – NRL airborne requirement for remote sensing and ocean color monitoring • Hyperspec VS15 – USAF airborne mine detection in littoral zones • Hyperspec VS15 – USN Predator-based project for Project Warhorse • Hyperspec VS15 – NRL Ocean PHILLS (Portable Hyperspectral Imager for Low Light Spectroscopy) sensor • Hyperspec VS15 - Project Darkhorse utilizing VNIR sensor • Hyperspec VS15 – AFRL LWIR sensor for polarimetric sensing for battlefield surveillance • Hyperspec VS25 – Selected by NASA for International Space Station deployment • Hyperspec VS25 – Optics deployed on Shadow UAV • Hyperspec VS – Custom UV/MCP unit deployed for AFRL missile plume tracking • Hyperspec VS50 – Airborne SWIR sensor • Micro-Hyperspec VNIR and NIR – Introduced in 2006 for UAV and SUGV deployment • Hyperspec VNIR – NASA augmentation for AVIRIS Example of Hyperspec™ Images The following is an example of a rendered image of a Natural Ruby utilizing the Hyperspec C-Series TM spectrometer with Headwall Photonics image processing software for Hyperspec . The rendered images depict were certain spectral response feature reside within the sample. Natural Ruby (Kenya)
  4. Headwall Photonics, Inc. Applicable to Multichannel Fiberoptic Array Detection and Multipoint Spatial Mapping In a typical application the input slit is a physical aperture located at the image plane of the objective lens, but this slit may also be comprised of several fiber optics creating a linear-array launch. The pinhole array mask is a good approximation of this, and allows fiber array performance to also be evaluated. A fiber array Hyperspec™ can be used as a staring array or a multi-channel single point spectrometer as shown below. Headwall has several configurations to offer for application specific performance. Individual spectra generated for each station Illumination Reference Process monitor station # 1 Process monitor station # 2 Process monitor station # 3 Process monitor station # 4 Process monitor station # 5 Calibration Reference Illumination λ Reference Calibration Reference #1 #2 #3 #4 #5 Process Monitoring Stations Conclusion: High performance spectral imaging has moved from advanced military applications to more affordable commercial solutions for a wide variety of applications. The high accuracy, sensitivity and dynamic range of totally reflective hyperspectral imagers is enabling research and commercial development of advanced spectral analysis techniques. Headwall Photonics has innovated several cost effective and performance differentiated sensor platforms which provide superior performance and flexibility to allow quick integration into traditional hyperspectral imaging techniques, as well as hyperspectral Raman spectroscopy. These systems support push-broom line scanning, multi-channel fiber optic and large volume fiber optic spatial mapping of spectral content within a sampled area. For more information, please contact: Jay Zakrzewski Director, Business Development Headwall Photonics, Inc. Tel: 978/353-4036 Email: