Bidirectional reflection distribution function (BRDF) models can accurately capture the reflective properties of target surfaces, thus playing a crucial role in achieving realistic image rendering in the field of computer graphics. The reflection model based on microfacet theory, which relies on a single roughness parameter, inadequately simulates the reflection properties of rough metal surfaces, thereby limiting rendering realism. To address this issue, we propose an improved method that introduces a glossiness parameter into the microfacet theory, thereby constructing the roughness-glossiness-Cook-Torrance (RGCT) reflection model. The glossiness parameter accurately captures the ratio and distribution of specular and diffuse reflections, which is directly related to the glossy properties of metal surfaces, enhancing the accuracy of the model in simulating the interaction between light and rough metal surfaces. We conducted comparative experiments on rough metal surfaces in the near-infrared wavelength bands with incidence angles from 0 to 90 deg. Experimental results demonstrate that compared to the traditional Cook-Torrance (CT) model based on microfacet theory, the RGCT model reduces the root mean square error (RMSE) by 0.0041 and 0.0048 on average, improves the coefficient of determination R2 by 0.0649 and 0.1082 on average, and reduces the relative error by 8.23% and 15.84% in the 1064 and 1550 nm wavelength bands, respectively. This improvement enhances the accuracy of the model in simulating the interaction between light and rough metal surfaces.
By fusing a low spatial resolution hyperspectral image (LR-HSI) and a high spatial resolution RGB image (HR-RGB), hybrid-resolution hyperspectral imaging has been a popular framework for acquiring high spatial resolution hyperspectral images (HR-HSIs). Existing fusion methods always employ a known spectral response function (SRF) of the RGB camera to reconstruct the HR-HSI. The SRF is often limited or unavailable in practice, restricting the performance of existing methods. To address this problem, we propose a color space transfer-based fusion strategy that obtains HR-HSIs based on a hybrid resolution hyperspectral imaging system without measuring the SRF. Specifically, using a clustered-based backpropagation neural network, the HR-RGB is mapped into the CIE XYZ color space, and the HR-XYZ is obtained. In the CIE XYZ color space, its SRF is known; thus, the the SRF measurement is successfully skipped. To efficiently fuse the HR-XYZ and the LR-HSI, we propose a polynomial fusion model that estimates the ratio matrix between the target HR-HSI and the upsampled LR-HSI. Finally, the target HR-HSI is reconstructed by combining the ratio matrix and the unsampled LR-HSI. Experimental results on two public data sets and our real-world data sets show that the proposed method outperforms five state-of-the-art fusion methods.
In the field of space exploration, it is often necessary to detect and identify the target under specific light source illumination and different observation angle conditions. Due to different shapes of the sample at different wavelengths of illumination source and geometry measurement conditions, the appearance of the obtained sample images are very different, and there are great differences between the apparent scale of the image and the inherent dimensions of the actual object. Using a standard reflector to calibrate the imaging system, the image or data can be corrected. In this paper, cylindrical sample is selected as the research object, a beam of 680nm parallel monochromatic light source is used for illumination, and the digital camera is used to photograph at a certain angular interval in the range of observation angle (0-75°), and the geometric dimension of the image pixel is calibrated. Through the calibration of image pixel geometry and the calculation of image gray value, the relationship between the gray value changes and the geometrical dimensions of the images captured under different imaging geometry conditions is studied. With the same wavelength light source lighting conditions, a bi-directional reflection distribution function (BRDF) calibration device was used to measure BRDF under multiple geometric conditions for the same material flat material. The BRDFs of material was used to study the appearance of the target sample, and the relationship between the image of the target sample and the corresponding BRDF of the material under different geometric conditions was analyzed and compared. A series of image processing data and methods for cylindrical samples are given in this paper, which has certain practical significance for the study of material properties and target imaging.
A project focuses on solving the problem of wavelength measurement of mercury lamps has been established, mainly in the air. Using the Fourier transform method, mercury lamp wavelengths are measured with high-precision, better than 0.1pm. By tracing back to the wavelength of the laser, the measuring device was calibrated very carefully using series frequency stabilized Lasers. The measurement uncertainty is better than 5pm (k=2), in the wavelength range of 250nm to 1100nm.
KEYWORDS: Color difference, LCDs, Single crystal X-ray diffraction, Visualization, Decision support systems, LED displays, Color reproduction, CIE 1931 color space, Data centers, Tolerancing
Using small color difference data sets (Macadam ellipses dataset and RIT-DuPont suprathreshold color difference
ellipses dataset), and large color difference data sets (Munsell Renovation Data and OSA Uniform Color Scales dataset),
the uniformity of several color spaces and performance of color difference formulae based on these color spaces are
evaluated. The color spaces used are CIELAB, DIN99d, IPT, and CIECAM02-UCS. It is found that the uniformity of
lightness is better than saturation and hue. Overall, for all these color spaces, the uniformity in the blue area is inferior to
the other area. The uniformity of CIECAM02-UCS is superior to the other color spaces for the whole color-difference
range from small to large. The uniformity of CIELAB and IPT for the large color difference data sets is better than it for
the small color difference data sets, but the DIN99d is opposite. Two common performance factors (PF/3 and STRESS)
and the statistical F-test are calculated to test the performance of color difference formula. The results show that the
performance of color difference formulae based on these four color spaces is consistent with the uniformity of these
color spaces.
Computed Tomography (CT) testing is an important non-destructive testing technology in industry inspection. So the
important work of CT development is the value calibration and the precise result judgment. Bi-directional reflection
distribution function(BRDF) as the common spatial characteristic parameter can be fit for the CT data structure in theory
level and the CT data cube can be calibrated using BRDF in both spectral and spatial. Deferent processing calibrated
images can be achieved by calibrating CT data in deferent dynamic range using corresponding BRDF absolute value.
Thus the influence of BRDF calibration to CT data can be achieved from these serial calibration data and the optimized
arithmetic model for this calibration is established. Furthermore, the uncertainty of this value traceability and calibration
is analyzed and a corresponding example in CT industry NDT is given which illustrate that this calibration is useful in
analysis of PT image because it provide more true image and reduce the probability of error judgment.
For measuring large-aperture optical system transmittance, a novel sub-aperture scanning machine with double-rotating
arms (SSMDA) was designed to obtain sub-aperture beam spot. Optical system full-aperture transmittance measurements
can be achieved by applying sub-aperture beam spot scanning technology. The mathematical model of the SSMDA
based on a homogeneous coordinate transformation matrix is established to develop a detailed methodology for
analyzing the beam spot scanning errors. The error analysis methodology considers two fundamental sources of scanning
errors, namely (1) the length systematic errors and (2) the rotational systematic errors. As the systematic errors of the
parameters are given beforehand, computational results of scanning errors are between -0.007~0.028mm while scanning
radius is not lager than 400.000mm. The results offer theoretical and data basis to the research on transmission
characteristics of large optical system.
KEYWORDS: Bidirectional reflectance transmission function, Uncertainty analysis, Sensors, Metrology, Xenon, Lamps, Light sources, Structural design, Control systems design, Process control
Low BRDF value is widespread used in many critical domains such as space and military fairs. These values below
0.1 Sr-1 . So the Absolute realization of these value is the most critical issue in the absolute measurement of BRDF. To
develop the Absolute value realization theory of BRDF , defining an arithmetic operators of BRDF , achieving an
absolute measurement Eq. of BRDF based on radiance. This is a new theory method to solve the realization problem of
low BRDF value. This theory method is realized on a self-designed common double orientation structure in space. By
designing an adding structure to extend the range of the measurement system and a control and processing software,
Absolute realization of low BRDF value is achieved. A material of low BRDF value is measured in this measurement
system and the spectral BRDF value are showed within different angles allover the space. All these values are below
0.4 Sr-1 . This process is a representative procedure about the measurement of low BRDF value. A corresponding
uncertainty analysis of this measurement data is given depend on the new theory of absolute realization and the
performance of the measurement system. The relative expand uncertainty of the measurement data is 0.078. This
uncertainty analysis is suitable for all measurements using the new theory of absolute realization and the corresponding
measurement system.
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.