We studied whether human observers can estimate the illumination direction from 3D textures of random Brownian surfaces, containing undulations over a range of scales. The locally Lambertian surfaces were illuminated with a collimated beam from random directions. The surfaces had a uniform albedo and thus texture appeared only through shading and shadowing. The data confirm earlier results with...

In this paper we present a new method for solving the uncalibrated photometric stereo problem in the Lambertian framework, based on the hypothesis that all lightings share the same intensity, which we can estimate. We show how this estimation allows one to solve the ambiguities of the linear Lambertian model, especially the so-called generalized bas-relief ambiguity. As the problem becomes well...

We examine light-trapping in thin crystalline silicon periodic nanostructures for solar cell applications. Using group theory, we show that light-trapping can be improved over a broad band when structural mirror symmetry is broken. This finding allows us to obtain surface nanostructures with an absorptance exceeding the Lambertian limit over a broad band at normal incidence. Further, we demonst...

In this paper, a novel framework is presented to recover the 3D shape information of a complex surface using its texture-less stereo images. First a linear and generalized Lambertian model is proposed to obtain the depth information by shape from shading (SfS) using an image from stereo pair. Then this depth data is corrected by integrating scale invariant features (SIFT) indexes. These SIFT in...

We propose a new figure of merit to assess the performance of light trapping nanostructures for solar cells, which we call the light trapping efficiency (LTE). The LTE has a target value of unity to represent the performance of an ideal Lambertian scatterer, although this is not an absolute limit but rather a benchmark value. Since the LTE aims to assess the nanostructure itself, it is, in prin...

Following Sugihara 23], we represent the geometric constraints imposed by the line-drawing of a polyhedron as a set of linear equalities and inequalities. Unlike him, we explicitly take into account the uncertainty in vertex position. This allows us to circumvent the superstrictness of the constraints without deleting any of them. For a given error bound, deciding whether a line-drawing is the ...

Determining the optimum number of suppliers and the optimum quantities to order from each of them is a critical problem for any supply chain. This paper has mathematically arrived at conditions to identify the appropriate sourcing strategy in a multi-period scenario for a stochastic supply and a stochastic demand environment. It has also obtained the total order quantity, optimum number of supp...