Patent ID: 8416418

Claim:
A method for detecting gold in a material sample, the method comprising: a) illuminating the material sample with light in a first preselected wavelength range less than 500 nm and with light in a second preselected wavelength range greater than 500 nm; b) detecting the light in the first preselected wavelength range reflected by the material sample and the light in the second preselected wavelength range reflected by the material sample, wherein the light is detected by an image sensor comprising a two-dimensional matrix of sensor elements; and c) computing, using a processor, a reflectance ratio product for each individual sensor element in the two-dimensional matrix of sensor elements, wherein the reflectance ratio product comprises the product of a wavelength reflectance ratio and a spatial reflectance ratio, wherein the wavelength reflectance ratio comprises relative intensity of the reflected light in the second preselected wavelength range to the reflected light in the first preselected wavelength range, and wherein the spatial reflectance ratio is computed based on the ratio of relative intensity of the reflected light in the second preselected wavelength range in each individual sensor element to relative intensity of the reflected light in the second preselected wavelength range in a plurality of sensor elements.