Two-dimensional bar code symbology using implicit version information

Abstract

A electro-optical memory includes a substrate on which is printed (or otherwise inscribed) a complex symbol or 'label' or 'bar code' of a high density two-dimensional symbology. The bar code contains component symbols or 'codewords' which are placed in row and column formation, with a variable number of codewords per row, and a variable number of rows. The symbology utilizes implicit bar code encoding scheme for implicit encoding the number of rows and the number of columns of codewords, as well as a predetermined amount of error correction. The symbology is capable of supporting a fixed number of bar code variants, with each variant having a predetermined number of rows and columns of codewords, and a predetermined error correction capability. For some codewords the implicit encoding scheme is combined with a gray coding scheme to reduce the inter-row codeword crosstalk. Systems are used for printing and decoding the bar codes of the invented symbology in applications where improved storage density and tight real estate requirements are of utmost importance. A memory may be used in conjunction with a scanner and a suitable control system in a number of applications, e.g., robotics operations or automated object searching.