Observers viewed computer-generated stereograms of randomly structured smooth surfaces and were required to judge the perceived local orientation at numerous probe points by adjusting a monocular gauge figure. The surfaces were depicted with specular or Lambertian reflectance functions, either with or without identifiable texture elements, and with varying directions of illumination. The result...

Under the Lambertian reflectance model, uncalibrated photometric stereo with unknown light sources is inherently ambiguous. In this paper, we consider the use of a more general reflectance model, namely the Torrance and Sparrow model, in uncalibrated photometric stereo. We demonstrate that this can not only resolve the ambiguity when the light sources are unknown, but can also result in more ac...

One robust method to reconstruct shape is photometric stereo (PMS), which reconstructs surface orientation using the Lambertian reflection properties of the surface material. To increase the applicability to non-Lambertian surfaces, we extend this method using a twostage process without introducing additional light sources or assuming a known micro facet distribution. In the first step, the glo...

The measurement of shape is a basic object inspection task. We use a noncontact method to determine shape called photometric stereo. The method uses three light sources which sequentially illuminate the object under inspection and a video camera for taking intensity images of the object. A significant problem with using photometric stereo is determining where to place the three light sources an...

This paper presents a novel approach for recovering the shape of non-Lambertian, multicolored objects using two input images. We show that a ring light source with complementary colored lights has the potential to be effectively utilized for this purpose. Under this lighting, the brightness of an object surface varies with respect to different reflections. Therefore, analyzing how brightness is...

Dielectric gratings are a promising method of achieving light trapping for thin crystalline silicon solar cells. In this paper, we systematically examine the potential performance of thin silicon solar cells with either silicon (Si) or titanium dioxide (TiO2) gratings using numerical simulations. The square pyramid structure with silicon nitride coating provides the best light trapping among al...

The firstand second-order optimum achievable exponents in the simple hypothesis testing problem are investigated. The optimum achievable exponent for type II error probability, under the constraint that the type I error probability is allowed asymptotically up to ε, is called the ε-optimum exponent. In this paper, we first give the second-order ε-optimum exponent in the case where the null hypo...

SFS (Shape From Shading) theory is based upon the Lambertian paradigm. Our visual demonstrations imply that this paradigm fails to apply to the conventional stimuli used to probe vision.