Biomedical subjects

Kristin J Dana

Publications and source records attributed to Kristin J Dana.

4 recordsLinked to original sources

PubMed2007

Polarization multiplexing and demultiplexing for appearance-based modeling.

Polarization has been used in numerous prior studies for separating diffuse and specular reflectance components, but in this work we show that it also can be used to separate surface reflectance contributions from individual light sources. Our approach is called polarization multiplexing and it has a significant impact in appearance modeling where the image as a function of illumination direction is needed. Multiple unknown light sources can illuminate the scene simultaneously, and the individual contributions to the overall surface reflectance are estimated. Polarization multiplexing relies on the relationship between the light source direction and the intensity modulation. Inverting this transformation enables the individual intensity contributions to be estimated. In addition to polarization multiplexing, we show that phase histograms from the intensity modulations can be used to estimate scene properties including the number of light sources.

Algorithms↗

PubMed2006

Relief texture from specularities.

In vision and graphics, advanced object models require not only 3D shape, but also surface detail. While several scanning devices exist to capture the global shape of an object, few methods concentrate on capturing the fine-scale detail. Fine-scale surface geometry (relief texture), such as surface markings, roughness, and imprints, is essential in highly realistic rendering and accurate prediction. We present a novel approach for measuring the relief texture of specular or partially specular surfaces using a specialized imaging device with a concave parabolic mirror to view multiple angles in a single image. Laser scanning typically fails for specular surfaces because of light scattering, but our method is explicitly designed for specular surfaces. Also, the spatial resolution of the measured geometry is significantly higher than standard methods, so very small surface details are captured. Furthermore, spatially varying reflectance is measured simultaneously, i.e., both texture color and texture shape are retrieved.

Algorithms↗

PubMed2004

Bidirectional imaging and modeling of skin texture.

In this paper, we present a method of skin imaging called bidirectional imaging that captures significantly more properties of appearance than standard imaging. The observed structure of the skin's surface is greatly dependent on the angle of incident illumination and the angle of observation. Specific protocols to achieve bidirectional imaging are presented and used to create the Rutgers Skin Texture Database (clinical component). This image database is the first of its kind in the dermatology community. Skin images of several disorders under multiple controlled illumination and viewing directions are provided publicly for research and educational use. Using this skin texture database, we employ computational surface modeling to perform automated skin texture classification. The classification experiments demonstrate the usefulness of the modeling and measurement methods.

Algorithms↗

PubMed2004

Device for convenient measurement of spatially varying bidirectional reflectance.

Capturing surface appearance is a challenging task because reflectance varies as a function of viewing and illumination direction. In addition, most real-world surfaces have a textured appearance, so reflectance also varies spatially. We present a texture camera that can conveniently capture spatially varying reflectance on a surface. Unlike other bidirectional imaging devices, the design eliminates the need for complex mechanical apparatus to move the light source and the camera over a hemisphere of possible directions. To facilitate fast and convenient measurement, the device uses a curved mirror so that multiple views of the same surface point are captured simultaneously. Simple planar motions of the imaging components also permit change of illumination direction and region imaging. We present the current prototype of this device, imaging results, and an analysis of the important imaging properties.

Journal Article↗