Abstract: A method for forming UPC or EAN bar code labels from scans of half labels or less than half labels requires that captured data be examined and classified as being either a first type of data configuration or a second type. A first type includes a given number of numeric characters delimited by both margin and center characters. A second type includes either a margin character or a center character and a given number of numeric characters. Labels are formed, where possible, by using appropriate first type data configurations. If labels cannot be formed using only first type configurations, second type configurations are examined to determine if they could represent different portions of the same region (left or right) of a label. If complementary second type configurations are found, they are merged to form a half label. The formed half label may be further merged with a complementary first type data configuration to form a complete label.

Abstract: A system is disclosed for preventing processing of duplicative coded label signals generated by a scanner lacking item detectors. The system establishes a variable lockout time as a function of operator performance. Any detected label candidate which duplicates a candidate received within the lockout time is assumed to be duplicative. Any transfer to the terminal is inhibited. Operator performance is tracked by measuring the inter-item arrival times for candidates actually transferred to the terminal. The inter-item arrival times are averaged over a given number of items. The average value is used to select a lockout time which is generally proportional to the average inter-item arrival time.

Abstract: Operating parameters for a multiple facet holographic disc scanner are adjusted on real time basis as a function of the actual diffraction efficiency of the facet region aligned with the impinging laser beam. The operating parameters are adjusted to achieve optimum signal levels independent of facet characteristics. Diffraction efficiency is inversely related to zero order beam power for a given level of input beam power. A photodetector measures the zero order beam power. The output of this photodetector is used to control video amplifier gain and/or semiconductor laser current.

Abstract: In decoding a UPC-type label, a partial decode and majority vote technique is employed to select final values for ambiguous characters (i.e., 1-7, 2-8) appearing in the label. During the partial decode phase, character-identifying values are established for every character but a common value is assigned to any ambiguous character in a given subset of such characters. An ambiguity-resolving value is additionally assigned to an ambiguous character each time it appears. Through algebraic summation of the ambiguity-resolving values for each character position occupied by an ambiguous character, the ambiguous character which appears a majority of times in that position is finally selected.

Abstract: A technique for compensating for systematic errors in printing or reading bar codes is disclosed. Label decoding always begins with a center character and proceeds one character at a time toward a margin. When bar-space pair measurements indicate an ambiguous character (which can only be fully decoded using bar width measurements) error correction is based on the characteristics of the adjacent, previously decoded character.