Surface Science for Vision and Graphics

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 which 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 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 enable change of illumination direction and region imaging. The original concept is described in [6], and [7] fully describes the current prototype of this device, imaging results, and an analysis of the important optical imaging properties. One of the imaging properties that we investigate is the spatial resolution effects due to changes in the illumination aperture. The finite size of the illumination aperture leads to a ray-bundle as opposed to a single ray. The cone angle of this incident illumination will vary depending on the position this ray bundle strikes the parabolic mirror. As in microscopy, the cone angle of incident illumination, or the numerical aperture, determines spatial resolution. We analyze the resolution for the texture camera and its dependence on illumination direction in [7].