KEYWORDS: Cameras, Line scan cameras, Calibration, 3D image reconstruction, Line scan image sensors, Image sensors, 3D modeling, Cultural heritage, Image resolution, 3D image processing
A Line-scan camera based stereo method for high resolution 3D image reconstruction is proposed. The imaging model of
a line scan camera is addressed in detail to describe the relationship between the coordinate of a physical object in space
and the coordinate of its image captured by the scanner. Affine-SIFT feature detector is utilized for establishing dense
stereo correspondence. Experimental result demonstrates the effectiveness and merit of this method to high resolution
digitization of cultural heritages.
We proposed a Bayesian method for estimating the system spectral sensitivities of a color imaging device such
as a scanner and a camera from an acquired color chart image. The system sensitivities are defined by the
product of spectral sensitivities of camera and spectral power distribution of illuminant, and characterize color
separation. In addition we proposed a scheme for predicting the optimal filter to increase color accuracy of
the device based on the estimated sensitivities. The predicted filter is attached to the front of camera and
modifies the system spectral sensitivities. This study aimed to improve color reproduction of the imaging
device in practical way even if the spectral sensitivities of the device are unknown. The proposed method is
derived by introducing the non-negativity, the smoothness and the zero boundaries of the sensitivity curves as
prior information. All hyperparameters in the proposed Bayesian model can be determined automatically by
the marginalized likelihood criterion. The modified system sensitivities and their color accuracy are predicted
computationally. An experiment was carried out to test the performance of the proposed method for predicting
the color accuracy improvement using two scanners. The average color difference was reduced from 3.07 to 2.04
and from 2.11 to 1.77 in the two scanners.
This paper presents a new approach for analyzing spectroscopic characteristic of metallic surfaces using spectroscopic
and image analysis. This method is useful for contactless and non destructive analysis of cultural heritage. Spectral
luminance, CIELAB, and CIEXYZ value of more than 80 metallic surfaces were measured with spectrometer and
scanned to examine spectroscopic characteristics of foils by using multiband images. This analysis through imaging can
improve the method for extracting difference related to types of metallic foils. Firstly, the spectral reflectance of each foil
was measured ranging from 220 to 850 nm in steps of 1 nm. The images were captured with color and monochromatic
camera using color filter in order to analyze the targets by multispectral approach. Then, principal component analysis
(PCA) was conducted with image pixel value of each target. The results have shown that the spectral reflectance whose
peak and change rate at a particular wavelength region differed from each foils, and that the multispectral images
extracted the difference in spectral characteristics related to different types of metallic foils and Japanese papers. This
could be useful in distinguishing among foils. This provides some promise that unknown metallic foils can be identified
through the measurement of their spectroscopic features.
Numerous cultural heritage art works have shiny surfaces resulting form gold, silver, and other metallic pigments. In
addition varnish overlayer on oil paintings makes it challenging to retrieve true color information. This is due to the
great effect of lighting condition when images are acquired and viewed. The reflection of light from such surfaces is a
combination of the surface's specular and diffused light reflections. In this paper, this specific problems encountered
when digitizing cultural heritage were discussed. Experimental results using the images acquired with a high-resolution
large flat bed scanner, together with a mathematical method for processing the captured images were presented and
discussed in detail. Focus was given in separating the diffused and specular components of the reflected light for the
purpose of analytical imaging. The mathematical algorithm developed in this study enables imaging of cultural
heritage with shiny and glossy surfaces effectively and efficiently.
Pigment degradation has been a subject of interest among researchers in the field of cultural heritage studies. Knowing
how pigments behave when subjected to different elements such as high temperature, humidity, electromagnetic
radiation and many more others is of prime importance. In this study, the effects of subjecting Japanese pigments to
high temperature were investigated. Focus was given on the effects in terms of pigment discoloration and the
micromechanism of degradation. Multispectral images were used to track the changes in color and spectral reflectance
by reconstructing colorimetric and spectral information from the images. The multispectral images were taken using a
high-resolution flat-bed scanner equipped with a line-CMOS camera. In addition, the pigments were characterized using
commercially available spectrometers, X-ray diffraction, X-ray fluorescence spectroscopy and X-ray absorption fine
structure were used to ascertain the influence of high temperature exposure of the pigments. The high resolution
multispectral scans gave the most valuable insights into the discoloration and micromechanism of pigment degradation
since they provide both analytical and visual information.
Interests in cultural heritage have grown tremendously in the past few years. These interests vary from preservation,
restoration, inspection and archiving just to name a few. Access to cultural heritage is very limited. Therefore, it is
important to maximize such opportunity to gather as much information as possible from the cultural heritage. In this
study, a technique was proposed to extract analytical information from digitally archived images. The images were
acquired at high resolution using a flatbed scanner equipped with a line CCD under fluorescent light illumination. The
images were used to reconstruct spectral reflectance using the pseudoinverse method. The results were used for pigment
identification and investigation on degradation. Three methods were explored in computing the conversion matrix which
contains information from the light source and the camera based on over 600 Japanese pigments as learning samples: (1)
use of all pigments in the database; (2) exclusion of some pigments if historical information is available on the sample;
and (3) color classification using L*C*H* color space. The technique was applied to the analysis of a real cultural
heritage, a hanging scroll painting called Dragon King Zennyo Ryu'o (classified as a Japanese National Treasure, dated
1145) found in Koya Mountain in Japan. The analytical information extracted from the archived images provided
insights on the degradation process the painting underwent. In addition, the traces of material detected from the analysis,
give art historians scientific proof in creating historical footprints for this precious cultural artifact. This study
demonstrated how archived RGB images could be used for the noninvasive and nondestructive investigation of actual
cultural heritage.
Common analysis techniques for artworks, such as X-ray based techniques, usually employ high-energy radiation
sources. It also oftentimes requires the removal of material from the sample making the analysis relatively destructive.
This is unacceptable for samples with high cultural value. Therefore, there is a need to develop alternative
nondestructive and noninvasive analysis methods. This paper presents an approach for pigment estimation of Japanese
paintings. Reflectance spectra were reconstructed from the RGB values of digital images with the help of multiple linear
regression analysis. A reference database with the measured reflectance spectra of the most common pigments used in
Japanese artworks was developed and used for identification by comparison and matching. Results have shown that
estimation can be successfully performed with only 2% error. The estimation results show some promise that the system
could become a powerful tool for the analysis of cultural heritage.
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