Optical mark reader

摘要

Each data point within a two-dimensional code can be represented by a distribution of spots. Each spot can be made small enough to be invisible to the human eye so that the two-dimensional code can be invisible on or within transparent or nontransparent materials. The spots can be spaced at a large distance to increase the signal-to-noise ratio for an optical code reader. A code reader can be adapted to read the spots and determine the data points.

主权项

1. A method for reading a two-dimensional identification code within a substrate having first and second opposing surfaces, comprising:
directing light toward a first surface of the substrate, wherein the light has a wavelength, and wherein the substrate is transparent to the wavelength, wherein the two-dimensional code is represented by a distribution of spots within the substrate, wherein the distribution of spots comprises multiple groups of spots, including first and second groups of spots, wherein each of the first and second groups of spots is representative of a geometric shape, such that the distribution of spots forms an array of multiple rows and columns of geometric areas, wherein some of the geometric areas include one group of spots and some of the geometric areas are devoid of spots, wherein a first portion of the light is blocked by the spots, and wherein a second portion of the light passes beyond the spots and propagates through the second surface of the substrate; magnifying the second portion of the light that propagates through the second surface of the substrate; imaging with an imager the second portion the light that propagates through the second surface of the substrate and is magnified; analyzing an image of the second portion of the light and shadows caused by blockage of the first portion of the light to determine the distribution of the spots; and determining the two-dimensional code based on the distribution of the spots imaged by the imager.