A Study of Metameric Blacks for the Representation of Spectral Images
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Spectral images contain a large volume of data and can be efficiently compressed by low dimensional linear models. However, there is a trade-off between the accuracy of spectral and colorimetric representation. When a spectral image is reproduced by a low-dimensional linear model, spectral error and color difference are contrary to each other and minimizing the colour error is by no means equivalent to minimizing the spectral error. Although one aim of a spectral-image file format is to preserve and represent the spectral information, most users are likely to reproduce a spectral image on a trichromatic image-reproduction system and therefore it is important that the spectral information is not preserved at the expense of colorimetric accuracy. In this study a method for spectral encoding that provides an efficient representation of the spectral information whilst perfectly preserving the colorimetric information is analysed. The lossy compression technique that is considered in this work is based on a low-dimensional linear model of spectral reflectance, with the first three basis functions represent color information and the additional basis functions are metameric blacks which preserve spectral information.Keywords:
Lossy compression
Representation
Basis (linear algebra)
Spectral bands
Spectral shape analysis
Spectral resolution
A new method of non-destructive quality inspection of fruits was investigated based on multi-spectral imaging technology,and the system was also developed,which consists of lighting chamber、multi-spectral light source、CCD camera.According to the basic color theory multi-spectral images were abstained by this system,and analyzed using multi-spectral images fusion methods.It was found that the multi-spectral images had the highest recognition rate when the spectral bands of multi-spectral fusion images are red spectral band,yellow spectral band and near infrared spectral band.The best multi-spectral imaging which make the defect detection easy is obtained under the new method,then we used the image processing algorithm such as Otsu to detect the defect.It was shown by the experiment that the defects can be detected easily using multi-spectral detection technology on non-destructive.
Spectral bands
Full spectral imaging
Spectral Analysis
Spectral shape analysis
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In this paper, a dual-channel spectral imaging system with agile spectral band access and spectral bandwidth tuning capability is presented. A diffractive grating is used as the spectral dispersion element for the dual-channel spectral imaging system. A 4-f spectral filtering channel using an adjustable slit is set up at the first diffraction order of the grating to realize coarse spectral band selection. An acousto-optic tunable filter selectively filters the spectrum of the non-dispersed zero order to realize fine spectral imaging. The spectral zooming function is achieved without increasing spectral frame number facilitating real-time spectral imaging operation. Feasibility of the spectral imaging has been demonstrated through preliminary experiments. Minimum 6 nm spectral resolution and 1.2° field of view have been achieved. The real-time spectral imaging capable of wide spectral band operation without loosing desired fine spectral capability is particularly useful for a variety of defense, medical, and environmental monitoring applications.
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Spectral imaging techniques extract spectral information using dispersive elements in combination with optical microscopes. For rapid acquisition, multiplexing spectral information along one dimension of imaged pixels has been demonstrated in hyperspectral imaging, as well as in Raman and Brillouin imaging. Full-field spectroscopy, i.e., multiplexing where imaged pixels are collected in 2D simultaneously while spectral analysis is performed sequentially, can increase spectral imaging speed, but so far has been attained at low spectral resolutions. Here, we extend 2D multiplexing to high spectral resolutions of ∼80 MHz (∼0.0001 nm) using high-throughput spectral discrimination based on atomic transitions.
Spectral resolution
Imaging Spectroscopy
Full spectral imaging
Chemical Imaging
Spectral envelope
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A dual-channel spectral imaging system with agile spectral band access and spectral bandwidth tuning capability is presented. A diffractive grating and an acousto-optic tunable filter (AOTF) are respectively used as spectral dispersion and spectral filtering elements for the two channels. A 4f spectral filtering channel using an adjustable slit is set up at the first diffraction order of the grating to realize coarse spectral band selection. The AOTF selectively filters the spectrum of the nondispersed zero order to realize fine spectral imaging. The spectral zooming function is achieved without increasing spectral frame number facilitating real-time spectral imaging operation. Feasibility of the spectral imaging has been demonstrated through preliminary experiments. Minimum 6 nm spectral resolution and 1.2 degrees field of view have been achieved. The real-time spectral imaging capable of wide spectral band operation without loosing desired fine spectral capability is particularly useful for a variety of defense, medical, and environmental monitoring applications.
Spectral resolution
Spectral envelope
Spectral bands
Spectral shape analysis
Full spectral imaging
Imaging Spectroscopy
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LC-based tunable filter with large aperture has been developed utilizing the effect of electric controlled birefringence. Spectral test indicated that this filter can operate in the visible band with an average 20 nm FWHM. A small scale spectral imaging system was established based on this tunable filter. Spectral imaging experiments on a certain number of samples show that this system can be tuned continuously with random-access selection of any wavelength, and has a higher level of resolving power in respect of both imaging and spectral tuning in the visible band, which has a brilliant application potentiality in biology, iatrology, environmental protection, resource detection through hyper-spectral imaging or ultra-spectral imaging.
Imaging Spectroscopy
Spectral bands
Narrow-band imaging
Coded aperture
Spectral width
Visible spectrum
Full spectral imaging
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We successfully demonstrated a multispectral remote sensing system based on our reported spectral imaging design. Dynamic spatial filters such as electronically selected slits were used to select desired bandpass spectrum at a Fourier plane of its optical system. Minimum 9 nm spectral resolution and 0.6° field of view has been achieved. In addition, compact prototype system packaging with a dimension of 17×11×8 inch has been attained. The real-time spectral imaging system capable of wide spectral band operation with simultaneous fine spectral resolution is particularly useful for a variety of defense, medical, and environmental monitoring applications.
Multispectral pattern recognition
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LC-based spectral imaging is a novel spectral imaging technology using the liquid crystal tunable filter(LCTF), which is a miniaturized device based on the electrically controlled birefringence of nematic liquid crystal. Continuously tuning electrically controlled through a spectral coverage is realized using LCTF under low voltages. Spectral imaging system based on LCTF is a miniaturized, multi-functional and real-time system with high spatial resolution and spectral resolution, which means that more and further information about the Earth and its resources can be acquired for new applications in large-scale mapping and environmental monitoring. LC-based tunable filter with large aperture has been developed utilizing the effect of electric controlled birefringence. Spectral test indicates that this filter can operate on the visible band with average 20 nm FWHM. A small scale spectral imaging system is established based on this tunable filter. Spectral imaging experiments on certain number of samples show that this system can provide continuously, and random-access selection of any wavelength, and has a higher level of resolving power in respect of both imaging and spectral tuning in the visible band, which indicates a brilliant application potentiality in environmental protection, resource detection.
Spectral resolution
Spectral bands
Imaging Spectroscopy
Coded aperture
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Imaging spectrometry for the remote sensing of the Earth is introduced. Reflected solar energy from the surface is dispersed in a spectrometer and used to form up to 200 registered spectral images. Each pixel has associated with it sufficient information for the reconstruction of a complete reflectance spectrum. The technique allows the diagnostic narrow band spectral features that are characteristic of many surface materials to be used to identify those materials. These spectral features are typically 20 to 40 nm wide; spectral imaging systems which acquire data in contiguous 10 nm bands therefore have sufficient resolution for direct identification of those materials with diagnostic spectral bands.
Imaging spectrometer
Spectral resolution
Imaging Spectroscopy
Full spectral imaging
Spectral bands
Spectral signature
Identification
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Recent technological developments permit improved instrumentation for surveillance and resource monitoring, but tradeoffs of spectral resolution and number of spectral bands versus spatial resolution and measurement precision must be considered. A band selection procedure is applied to high spectral resolution (0.01 /spl mu//m) aircraft sensor imagery representing the visible and near-infrared wavelengths (0.4-2.5 /spl mu/m). Approximately 30-40 spectral bands characterize virtually all the information (variability) in the data, with the precise number depending on issues of data interpretation. This suggests that lower spectral resolution and higher spatial resolution are preferable to the reverse. Further study is needed to evaluate the significance of spectral bands having very low amplitude variability.
Spectral resolution
Spectral bands
Instrumentation
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There is currently a search for an automated, objective and non-invasive system that would accurately diagnose pigmented skin tumours. Systems that measure either the spatial or the spectral characteristics of light reflected from the skin have shown promise for this purpose but only a few studies have combined spatial and spectral information. We plan to study this and consequently need to construct a cost-effective research spectral imaging system but the design will require a compromise between spatial and spectral information. Here, the effect, on diagnostic accuracy, of reducing the spectral resolution of spectrophotometry data was studied. Also studied was the effect of reducing the spectral range to that of the sensitivity range of low-cost detectors. There was no significant fall in the diagnostic power when the spectral resolution was reduced from 3.8nm to 50nm, and when the spectral range was reduced from 320-1100nm to 400-1000nm. Therefore, in the design of the spectral imaging system emphasis was placed on spatial resolution and a standard detector was used. The spectral imaging system contains a broadband light source, diffraction grating monochromator and CMOS camera and achieves 10nm spectral resolution over a spectral range of 400-1000nm, with a spatial resolution of 40 microns over a field of view of 2cm.
Spectral resolution
Full spectral imaging
Spectral sensitivity
Imaging Spectroscopy
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