1,708 research outputs found
The Scattering Approach to the Casimir Force
We present the scattering approach which is nowadays the best tool for
describing the Casimir force in realistic experimental configurations. After
reminders on the simple geometries of 1d space and specular scatterers in 3d
space, we discuss the case of stationary arbitrarily shaped mirrors in
electromagnetic vacuum. We then review specific calculations based on the
scattering approach, dealing for example with the forces or torques between
nanostructured surfaces and with the force between a plane and a sphere. In
these various cases, we account for the material dependence of the forces, and
show that the geometry dependence goes beyond the trivial {\it Proximity Force
Approximation} often used for discussing experiments.Comment: Proceedings of the QFEXT'09 conference (Oklahoma, 2009
Reducing spectral reflections through image inpainting
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Includes bibliographical references (p. 45-46).The goal of this thesis is to produce an image processing tool that could, with limited user interaction, significantly reduce spectral reflections. The resulting process can then be used by biological researchers in the process of cataloging and recognizing individual organisms via collected images. The process involves the generation of a mask, refinements to that mask such as background segmentation and morphological dilation, and finally the inpainting of the specular regions. This method improves on existing single pixel methods by incorporating both color and texture infilling of the specular reflections. It also works on images with no special setup or preparation.by Joshua Runge.M.Eng
Recovery of surface orientation from diffuse polarization
When unpolarized light is reflected from a smooth dielectric surface, it becomes partially polarized. This is due to the orientation of dipoles induced in the reflecting medium and applies to both specular and diffuse reflection. This paper is concerned with exploiting polarization by surface reflection, using images of smooth dielectric objects, to recover surface normals and, hence, height. This paper presents the underlying physics of polarization by reflection, starting with the Fresnel equations. These equations are used to interpret images taken with a linear polarizer and digital camera, revealing the shape of the objects. Experimental results are presented that illustrate that the technique is accurate near object limbs, as the theory predicts, with less precise, but still useful, results elsewhere. A detailed analysis of the accuracy of the technique for a variety of materials is presented. A method for estimating refractive indices using a laser and linear polarizer is also given
Photometric stereo for strong specular highlights
Photometric stereo (PS) is a fundamental technique in computer vision known
to produce 3-D shape with high accuracy. The setting of PS is defined by using
several input images of a static scene taken from one and the same camera
position but under varying illumination. The vast majority of studies in this
3-D reconstruction method assume orthographic projection for the camera model.
In addition, they mainly consider the Lambertian reflectance model as the way
that light scatters at surfaces. So, providing reliable PS results from real
world objects still remains a challenging task. We address 3-D reconstruction
by PS using a more realistic set of assumptions combining for the first time
the complete Blinn-Phong reflectance model and perspective projection. To this
end, we will compare two different methods of incorporating the perspective
projection into our model. Experiments are performed on both synthetic and real
world images. Note that our real-world experiments do not benefit from
laboratory conditions. The results show the high potential of our method even
for complex real world applications such as medical endoscopy images which may
include high amounts of specular highlights
Estimating Reflectance Layer from A Single Image: Integrating Reflectance Guidance and Shadow/Specular Aware Learning
Estimating reflectance layer from a single image is a challenging task. It
becomes more challenging when the input image contains shadows or specular
highlights, which often render an inaccurate estimate of the reflectance layer.
Therefore, we propose a two-stage learning method, including reflectance
guidance and a Shadow/Specular-Aware (S-Aware) network to tackle the problem.
In the first stage, an initial reflectance layer free from shadows and
specularities is obtained with the constraint of novel losses that are guided
by prior-based shadow-free and specular-free images. To further enforce the
reflectance layer to be independent from shadows and specularities in the
second-stage refinement, we introduce an S-Aware network that distinguishes the
reflectance image from the input image. Our network employs a classifier to
categorize shadow/shadow-free, specular/specular-free classes, enabling the
activation features to function as attention maps that focus on shadow/specular
regions. Our quantitative and qualitative evaluations show that our method
outperforms the state-of-the-art methods in the reflectance layer estimation
that is free from shadows and specularities.Comment: Accepted to AAAI202
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