Spectral Reflectance Of Samples Research Articles

Construction of Spectral Discoloration Model for Red Lead Pigment by Aging Test and Simulating Degradation Experiment

The construction of spectral discoloration model, based on aging test and simulating degradation experiment, was proposed to detect the aging degree of red lead pigment in ancient murals and to reproduce the spectral data supporting digital restoration of the ancient murals. The degradation process of red lead pigment under the aging test conditions was revealed by X-ray diffraction, scanning electron microscopy, and spectrophotometer. The simulating degradation experiment was carried out by proportionally mixing red lead and lead dioxide with referring to the results of aging test. The experimental result indicated that the pure red lead was gradually turned into black lead dioxide, and the amount of tiny particles of the aging sample increased faced with aging process. Both the chroma and lightness of red lead pigment decreased with discoloration, and its hue essentially remains unchanged. In addition, the spectral reflectance curves of the aging samples almost started rising at about 550 nm with the inflection moving slightly from about 570 nm to 550 nm. The spectral reflectance of samples in long- and in short-wavelength regions was fitted well with the logarithmic and linear function. The spectral discoloration model was established, and the real aging red lead pigment in Dunhuang murals was measured and verified the effectiveness of the model.

Relative Translucency and Surface Roughness of Four Yttrium-stabilized Tetragonal Zirconia Polycrystalline-based Dental Restorations

Background Yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) has become one of the most popular restorative core materials in the last decade due to its high flexural strength and fracture toughness. However, the low translucency of Y-TZP has become a critical issue in shade matching to natural teeth. This study compared the translucency of Y-TZP and alumina core materials at clinically appropriate thicknesses. Methods Zirconia disc samples were fabricated from Cercon (Dentsply Degudent), Everest (Kavo), Lava (3M ESPE) with 0.5-mm thickness and Procera zirconia (Nobel Biocare) with 0.4-mm thickness. Procera alumina samples with 0.4-mm thickness were also made for comparison. Spectral reflectance of samples was measured and contrast ratios were calculated. Surface roughness (Ra) of all ceramic discs was also analyzed with a Profilometer. Results One-way ANOVA showed a significantly lower translucency of Cercon than all the other three types of zirconia materials. Procera Alumina also demonstrated significantly higher translucency than all four types of zirconia. The mean Ra of Procera zirconia was significantly higher than the other types of ceramic materials. Conclusion The Ra of the Procera zirconia group was significantly higher than all the other testing groups.

Research on Reconstruction of Spectral Reflectance Based on Principal Component Analysis

Traditional color reproduction technology based on the Metamerism principle, the disadvantage is that different observer condition leads to different color appearance.To fulfill the color consistency, the spectrum reflectance of the object color sample need to be reconstructed. The principal component analysis makes use of the linear combination of a few principal components to reconstruct the spectral reflectance of sample. This paper analyzes the 31*31 matrix of Munsell spectral data by the principle component analyze method and achieves the principal component for spectrum reflectance. The numbers of principal components are identified as six by discussing the variance contribution rate. Spectral reconstruction of four Munsell testing samples makes use of first six principal components, which has met the accuracy requirements. Research shows that the reconstruction of spectral accuracy decreased when training samples and testing samples belong to the different database.

Measurement of the spectral reflectance of samples of absorbing coatings in the wavelength range 350–1100 nm with angles of incidence of the radiation 0–90°

A plant and method of measurement of the spectral reflectance of samples of absorbing coatings of solar energy collectors situated at the center of an integrating sphere in the range of wavelengths 350–1100 nm and at angles of incidence 0–90° are described. Features of the process of measuring the diffuse optical density in reflected light are investigated. Results of measurements of the spectral reflectance of the samples in the above range of wavelengths are presented and a calculation of the integral reflectance at angles of incidence of the radiation 5–85° is also carried out.

Suppression of Noise Effects in Color Correction by Spectral Sensitivities of Image Sensors

The accurate transformation of device responses to tristimulus values is important at an early stage in color management and this transformation is usually called color correction. In this paper it is shown that the influence of noise on color correction can be suppressed if the square of the singular values by the singular value decomposition (SVD) of a sensor matrix represented by surface reflectance, SLVA1/2, is larger than the noise variance, where S is the M × N matrix of M channel spectral sensitivities, L is the N × N diagonal matrix for an recording illuminant, V is the N × N matrix which is composed of eigenvectors of an autocorrelation matrix for spectral reflectance of samples, A is the N × N diagonal matrix with eigenvalues of the autocorrelation matrix along the diagonal and N is the number of the dimension, respectively. A method to suppress the influence of noise on color correction by spectral sensitivities of sensors is presented for the first time.

Color Tolerances as Affected by Changes in Composition and Intensity of Illumination and Reflectance of Background

The hue, lightness, and saturation of any object depend upon a complex of conditions, chief of which are spectral reflectance of sample and background, spectral energy distribution of illuminant, and state of the visual mechanism as determined by its properties as a receptor and mode of functioning. Since color tolerance concerns the extent to which colors match, or if they do not match, in what respects they differ, any factors which affect the color of standard and variables have importance for the problem of tolerance. HOW illuminant, background, contrast, adaptation, and so-called constancy operate in literally 'coloring' objects seems to be nearing solution after recent work with strongly chromatic illuminants and backgrounds of high, medium, and low reflectance.1 The principles governing color changes which objects undergo in strongly chromatic illuminations throw light also