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1.
Ultraviolet and visible imaging and spectrographic imaging instrument   总被引:1,自引:0,他引:1  
The Ultraviolet and Visible Imaging and Spectrographic Imaging experiment consists of five spectrographic imagers and four imagers. These nine sensors provide spectrographic and imaging capabilities from 110 to 900 nm. The spectrographic imagers share an off-axis design in which selectable slits alternate fields of view (1.00° × 0.10° or 1.00° × 0.05°) and spectral resolutions between 0.5 and 4 nm. Image planes of the spectrographic imager have a programmable spectral dimension with 68, 136, or 272 pixels across each individual spectral band, and a programmable spatial dimension with 5, 10, 20, or 40 pixels across the 1° slit length. A scan mirror sweeps the slit through a second spatial dimension to generate a 1° × 1° spectrographic image once every 5, 10, or 20 s, depending on the scan rate. The four imagers provide narrow-field (1.28° × 1.59°) and wide-field (10.5° × 13.1°) viewing. Each imager has a six-position filter wheel that selects various spectral regimes and neutral densities. The nine sensors ut lize intensified CCD detectors that have an intrascene dynamic range of ~ 10(3) and an interscene dynamic range of ~ 10(5); neutral-density filters provide an additional dynamic range of ~ 10(2-3). The detector uses an automatic gain control that permits the sensors to adjust to scenes of varying intensity. The sensors have common boresights and can operate separately, simultaneously, or synchronously. To be launched aboard the Midcourse Space Experiment spacecraft in the mid-1990's, the ultraviolet and visible imaging and spectrographic imaging instrument will investigate a multitude of celestial, atmospheric, and point sources during its planned 4-yr life.  相似文献   

2.
Cheng X  Wang J  Xue Q  Hong Y  Li S 《Applied optics》2011,50(35):6446-6451
A field-of-view-folding approach is proposed to extend the field of view (FOV) of a dispersive imaging spectrometer after introducing several linear arrays of imaging fiber bundles to which to replace the slit. The fiber bundles can flexibly connect fore-optics with a spectrometer to yield an imaging fiber-optic spectrometer (IFOS). The technology of FOV segmenting and folding, which can decrease simultaneously the dimension and spectral distortion of the imaging spectrometer, is described in detail. Because of the sampling function of the fiber bundles, the IFOS is a double-sampling imaging system. We analyze the effect of fiber coupling on the modulation transfer function (MTF) and then develop a cascade MTF model to estimate the imaging performance of the IFOS. A spaceborne IFOS example is presented to describe how the method can be used.  相似文献   

3.
Radar imaging     
Radar systems combining coherent signals with frequency and angular diversity offer the possibility of synthesizing images of complex objects with spatial resolution of a few wavelengths. The availability of high-quality microwave sources and components, high-speed digital computers, and efficient signal-processing algorithms allows radar imaging to be implemented in laboratory environments using commercially-available equipment. The paper summarizes fundamental issues by addressing conceptual and practical limits of radar imaging and presents examples obtained from results of measurements in a laboratory environment. Implementation details of sophisticated operational imaging radars are not covered.©1993 John Wiley & Sons Inc  相似文献   

4.
NIR imaging     
《Materials Today》2003,6(7-8):57
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5.
《Materials Today》2002,5(12):62
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6.
Catheter-based imaging of atherosclerosis with high resolution, albeit invasive, is extremely important for screening and characterization of vulnerable plaques. Currently, there is a need for an imaging technique capable of providing comprehensive morphological and functional information of plaques. In this paper, we present an intravascular photoacoustic imaging technique to characterize vulnerable plaques by using optical absorption contrast between normal tissue and atherosclerotic lesions. Specifically, we investigate the feasibility of obtaining intravascular photoacoustic (IVPA) images using a high-frequency intravascular ultrasound (IVUS) imaging catheter. Indeed, the combination of IVPA imaging with clinically available IVUS imaging may provide desired functional and morphological assessment of the plaque. The imaging studies were performed with tissue-mimicking arterial vessel phantoms and excised samples of rabbit artery. The results of our study suggest that catheter-based intravascular photoacoustic imaging is possible, and the combination of IVPA with IVUS has the potential to detect and differentiate atherosclerosis based on both the structure and composition of the plaque.  相似文献   

7.
Neifeld MA  Shankar P 《Applied optics》2003,42(17):3379-3389
We analyze the performance of feature-specific imaging systems. We study incoherent optical systems that directly measure linear projects of the optical irradiance distribution. Direct feature measurement exploit, the multiplex advantage, and for small numbers of projections can provide higher feature-fidelity than those systems that postprocess a conventional image. We examine feature-specific imaging using Wavelet, Karhunen-Loeve (KL), Hadamard, and independent-component features, quantifying feature fidelity in Gaussian-, shot-, and quantization-noise environments. An example of feature-specific imaging based on KL projections is analyzed and demonstrates that within a high-noise environment it is possible to improve image fidelity via direct feature measurement. A candidate optical system is presented and a preliminary implementational study is undertaken.  相似文献   

8.
We review various narrow-band range-Doppler imaging methods that have been proposed for radar and highlight the difficulties in their implementation and their limitations. We also present two new imaging schemes. The first involves the transmission of multiplexed chirps, and the second involves simple frequency division multiplexing. The second approach seems to yield the most promising range-Doppler imaging methods.  相似文献   

9.
It is well known that millimetre-wave systems can penetrate poor weather, dust and smoke far better than infrared or visible systems. Imaging in this band offers the opportunity to be able to navigate and perform surveillance in these conditions of poor visibility. Furthermore, the ability to penetrate dielectrics such as plastic and cloth has opened up the opportunity of detecting weapons and contraband hidden under people's clothing. The optical properties of materials have a direct impact on the applicability of imaging systems. In the terahertz band solids have absorptions which can be assigned to vibrational modes. Lattice modes occur at the lowest frequencies and polythene, for example, has a lattice mode at 2.4 THz. Solids have no such absorptions in the millimetre bands (30-300 GHz) and image contrast is produced by differences in transmission, reflection and absorption. A novel, real-time, mechanically scanned, passive millimetre-wave imager has been designed. The antenna elements are based on a combination of a Schmidt camera and a conical scanner, both of which have their origins in optical systems. Polarization techniques, which were developed for operation in the centimetric band, are used to fold the optics. Both 35 GHz and 94 GHz versions have been constructed.  相似文献   

10.
Ghost imaging with a classical thermal source is investigated in a two-arm microscope imaging system. The dependence of the imaging visibility on the aperture of the reference lens is discussed. It is shown that by using large apertures, good visibility as well as enhancing resolution can be obtained. The effects from the distance the object is moved away from the original plane are also studied, and one can obtain good visibility with a well-resolved image by changing the distance.  相似文献   

11.
Baheti PK  Neifeld MA 《Applied optics》2006,45(28):7382-7391
We present a feature-specific imaging system based on the use of structured light. Feature measurements are obtained by projecting spatially structured illumination onto an object and collecting all the reflected light onto a single photodetector. Principal component features are used to define the illumination patterns. The optimal linear minimum mean-square error (LMMSE) operator is used to generate object estimates from the measured features. We study the optimal allocation of illumination energy into each feature measurement in the presence of additive white Gaussian detector noise and optical blur. We demonstrate that this new imaging approach reduces imager complexity and provides improved image quality in high noise environments. Compared to the optimal LMMSE postprocessing of a conventional image, feature-specific structured imaging provides a 38% rms error reduction and requires 400 times fewer measurements for a noise standard deviation of sigma = 2 x 10(-3). Experimental results validate these theoretical predictions.  相似文献   

12.
Zhan G  Oka K  Ishigaki T  Baba N 《Applied optics》2002,41(4):734-738
A Fourier-transform imaging spectrometer, believed to be novel, based on the Savart polariscope is presented. There is no slit in this instrument, which means that it has a high throughput. The principle and the system configuration are described. Several preliminary experimental results are shown.  相似文献   

13.
Large-aperture linear diffractive axicons are optical devices providing achromatic nondiffracting beams with an extended depth of focus when illuminated by white light sources. Annular apertures introduce chromatic foci separation, making chromatic imaging possible despite important radiometric losses. Recently, a new type of diffractive axicon has been introduced, by multiplexing concentric annular axicons with appropriate sizes and periods, called a multiple annular linear diffractive axicon (MALDA). This new family of conical optics combines multiple annular axicons in different ways to optimize color foci recombination, separation, or interleaving. We present different types of MALDA, give an experimental illustration of the use of these devices, and describe the manufacturing issues related to their fabrication to provide color imaging systems with long focal depths and good diffraction efficiency. Application to multispectral image analysis is discussed.  相似文献   

14.
Gallatin GM 《Applied optics》2001,40(28):4958-4964
The equation for partially coherent high-numerical-aperture scalar imaging was originally derived by Cole et al. [Jpn. J. Appl. Phys. 31, 4110 (1992)]. Here I present an alternative derivation, based on the plane-wave spectral representation of propagation, which can, at least in some respects, be viewed as more straightforward.  相似文献   

15.
A signal-subspace method is derived for the localization and imaging of unknown scatterers using intensity-only wave field data (lacking field phase information). The method is an extension of the time-reversal multiple-signal-classification imaging approach to intensity-only data. Of importance, the derived methodology works within exact scattering theory including multiple scattering.  相似文献   

16.
17.
《NDT International》1981,14(1):9-14
The important parameters of X-ray imaging tubes are considered in relation to their main components, the X-ray detection screen, the photocathode, the electron optics and the output screen. These parameters define the performance which can be achieved in terms of noise, contrast and resolution. Possible further improvements are also discussed.  相似文献   

18.
Nondestructive subharmonic imaging   总被引:4,自引:0,他引:4  
Ultrasound contrast agent microbubbles are intravascular agents that can be used to estimate blood perfusion. Blood perfusion may be estimated by destroying the bubbles in a vascular bed and observing the refresh of contrast agents back into the vascular bed. Contrast agents can be readily destroyed by traditional imaging techniques. The design of a nondestructive imaging technique is necessary for the accurate quantification of contrast agent refresh. In this work, subharmonic imaging is investigated as a method for nondestructive imaging with the contrast agent microbubble MP1950 (Mallinckrodt, Inc., St. Louis, MO). Optical observation during insonation, in conjunction with a modified Rayleigh-Plesset (R-P) analysis, provides insight into the mechanisms of and parameters required for subharmonic frequency generation. Subharmonic imaging with a transmission frequency that is the same as the resonant frequency of the bubble is shown to require a minimum pressure of insonation that is greater than the experimentally-observed bubble destruction threshold. Subharmonic imaging with a transmission frequency that is twice the resonant frequency of the bubble produces a subharmonic frequency response while minimizing bubble instability. Optimization is performed using optical experimental analysis and R-P analysis  相似文献   

19.
Optical polarization imaging   总被引:5,自引:0,他引:5  
Demos SG  Alfano RR 《Applied optics》1997,36(1):150-155
The temporal profiles of the parallel and perpendicular polarization components of a light pulse backscattered from a scattering medium are different. The depth of penetration into the tissue and depolarization of the backscattered light depend on the scattering and absorption characteristics of the tissue. Based on these facts, a novel technique is demonstrated for noninvasive surface and beneath-the-surface imaging of biological systems.  相似文献   

20.
Cotton DM  Cook T  Chakrabarti S 《Applied optics》1994,33(10):1958-1962
A spectrograph concept designed for both high wavelength and high spatial resolution (in one dimension) is briefly described. This design is referred to as a single-element imaging spectrograph (SEIS). It is a one-bounce diffractive system that combines the spectral properties of a Rowland mount spectrograph with the imaging (spatial resolution) properties of a Wadsworth mount spectrograph through the use of a toroidal diffraction grating. No primary optics are necessary, making the system especially attractive for use in the extreme and far ultraviolet, where low reflectivity of common optical coatings can severely limit instrument sensitivity.  相似文献   

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