Imaging spectroscopy (IS) extends the measurement of one-dimensional UV-VIS-NIR spectroscopy to two-dimensional
domain providing material characterization and localization. The technique is gaining importance for the study of
cultural heritage but its application is mainly focused on the analysis of pigments in paintings. An IS device has been
developed and then applied to the study of chromophores in glassy objects. It consists of a visible imaging
spectrograph, mounted on a rotation stage, which captures monochromatic images of the sample within a wavelength
range from 420 nm to 850 nm. The system has been used for the characterization and mapping of chromophores of
hundreds of coloured glass tesserae of the stained glass windows from the Scrovegni Chapel (Padua, Italy). Two
measurement methodologies have been performed: transmission and double-transmission modes. In the first case,
lamps used to illuminate the sample and the spectrograph are placed on the opposite side of the window, to acquire
directly the signal transmitted from the glass. In the latter case, the lamps and the spectrograph are placed on the same
side of the window, that is placed on a white scattering screen. The acquired signal comes from the light of the lamps
transmitted through the glass, then diffused back by the opaque white screen and finally transmitted again through the
glass. Results are discussed comparing both modalities in terms of signal-to-noise ratio and spectral contrast. Visible
spectra acquired allow the clear identification of several chromophores, e.g. Co(II), Cr(III) or Mn(III). The IS device
acquires numerous spectra in relatively short time in a non-invasive way. According to the authors knowledge, this is
the first time in which visible imaging spectroscopy technique has been applied for the study of stained glass windows.
As the results show, it could represent a powerful and innovative tool to map chromophores of this kind of artefact,
particularly when integrated with other non-invasive techniques as X-ray fluorescence.
The aim of this study is to assess angle-dependent systematic errors and measurement uncertainties for a conoscopic
holography laser sensor mounted on a Coordinate Measuring Machine (CMM). The main contribution of our work is the
definition of a methodology for the derivation of point-sensitive systematic and random errors, which must be
determined in order to evaluate the accuracy of the measuring system. An ad hoc three dimensional artefact has been
built for the task. The experimental test has been designed so as to isolate the effects of angular variations from those of
other influence quantities that might affect the measurement result. We have found the best measurand to assess angle-dependent
errors, and found some preliminary results on the expression of the systematic error and measurement
uncertainty as a function of the zenith angle for the chosen measurement system and sample material.
We present the recent results obtained by a system which measures both 3D shape and multispectral texture of artistic
and architectural cultural assets. The system consists on a rangefinder device which acquires the range and a visible
scanning spectrograph for colour texture analysis. This technique is applied to the acquisition of the cycle of Stories of
Maria, a frescoed lateral chapel painted by Girolamo Tessari in 1523-1526 located in the church of S. Francesco in
Padua (Italy).
In this paper, an integrated system based on a phase-shift laser scanning for measuring shape and a imaging spectrograph for measuring color is described. The system is designed for acquisition of large areas, such as chapels or frescoed walls. The phase-shift laser range-finder provides accurate distance measurement, up to 10 meters, pointing at most target surfaces through the measurement of the phase shift. The acquisition of a complete object is performed point by point by a 2D scanning. The imaging spectrograph measures the spectrum of the light coming from on a narrow rectangular region having width and height equal to the image of the entrance slit projected on the object plane. A complete 2D image is acquired by scanning the region in the direction perpendicular to the slit height. The merging of these multiple acquisitions yields the complete spectral and spatial description of the color of the object.
Data compression is quite relevant for storage and transmission of museal data. This work reports on the performance of subband coding applied to paintings pictures obtained by an HDTV camera. The performance of different analysis/synthesis filter banks and coding schemes is compared. The best results are obtained via Johnston's filters and a uniform threshold quantizer. The effectiveness of a scalable use of subband coding in this application is also reported.
The computation of an estimate of the autocorrelation function from available data enters a great number of signal processing applications and typically represents the bulk of the computation time required in each application. This work investigates frequency domain techniques for the evaluation of the autocorrelation of multidimensional signals: in particular, the extension of Rader's algorithm for 1D signals is considered. The bidimensional case is treated in detail because it is of special interest for applications and because the reasoning used can be readily applied to higher dimension signals. The direct extension of Rader's algorithm to the multidimensional case is not optimal with respect to the choice of the subblock dimension, unlike in the one dimensional case: a modified algorithm is proposed that allows further computational savings and is particularly attractive for the data organization. The computation time required by frequency domain techniques is evaluated in detail. The analysis confirms that the proposed frequency domain techniques lead to significant computation time savings.
A multispectral and low cost/performance ratio vision machine is here proposed. Integration and fusion of visual information are the main capabilities required to this architecture. Modulanty and system upgrading features are also taken in consideration in order develop a low cost/performance ratio vision machine. Two intimately linked hardware environments constitute the nodes ofthe proposed architecture: a VMEbus based subsystem is taylored for data acquisition, preprocessing, and general purpose number crunching, while an Apple MacIntosh is devoted to data and image display and to control the acquisition and processing procedure running on the VMEbus. Moreover the MacIntosh environment can be viewed as the software counterpart of the VMEbus for the modularity of its software packages. The system cost and performances are evaluated on the base of the market offering. The proposed architecture is taylored for the solution of a typical remote sensing problem: the terrain classification on the base of its thermal inertia.
The use of infrared imaging equipment for surface temperature measurements requires
the knowledge of parameters such as object emissivity, temperature of the object
surroundings and atmospheric transmittivity. The last two parameters can be evaluated from
the gray levels of a thermal reference put into the scene.
Accurate identification of the pixels belonging to the thermal reference but not to the
investigated objects or background has been so far performed by a human operator. Full
automation of such a task is highly desirable in actual practice, especially in applications
involving a large numbers of thermograms or sequences of them.
This work presents a method for the automatic detection of a Ohman thermal reference in
digitized thermograms. The thermographic applications of the procedure, including
automatic measurements of surface temperature and thermal parameters, are also described.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.