International Business Machines Corporation

George J Laurer

Robert L Cowardin

Robert Thomas Cato

Olen L Stokes

Eric C Broockman

Charles M Pierce

William D Gregory, Jr

An improved holographic scanner includes circuitry for adjusting the frequency with which an analog photodetector signal is sampled in accordance with the focal length of the scanning beam produced by the active holographic facet. Two embodiments are shown. In one embodiment, facet-edge signals are used to track the facets. A processor retrieves a predetermined frequency scaling factor appropriate for each facet. In the other embodiment, a holographic disk carries an auxiliary data track. The track has timing indicia with spatial frequencies dependent upon the focal length of the adjacent facet. The timing indicia are used to control the output of a voltage controlled oscillator in a circuit including a phase locked loop.

Halographic scanner having adjustable sampling rate

A fixed position optical scanner with a multi-faceted holographic disk includes circuitry for adjusting the lockout voltage as a function of the focal length of the active facet. The disk position is tracked to identify the active facet. A facet identifying signal is used to address a lockout table in processor memory. A digital value retrieved from the lockout table is converted to analog form and applied through a resistor to a voltage divider in the threshold circuit. The voltage divider scales down a white peak following voltage and compares it to a black peak following voltage. The facet-dependent lockout voltage biases the junction of the voltage divider to vary the effective lockout voltage as a function of the focal length of the currently active facet.

System for adjusting holographic scanner lockout voltage

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.

Decoding method for multicharacter labels

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.

Systematic error correction in bar code scanner

A scanning system includes a pair of buffer memories for alternately accumulating strings of signals which may contain bar coded label data. Candidate selection logic circuits examine incoming signals to generate a candidate signal when a string of signals satisfies gross logical tests. A control counter responds to the incoming signals and to the candidate signal to select an alternate buffer memory only when the active memory is fully loaded and contains at least part of a label candidate. The contents of the fully loaded memory are transferred to a processor for further analysis while incoming signals are routed to the alternate memory.

Buffer memory control circuit for label scanning system

A method and circuit for finding the beginning of valid coded information from a scanner reading a label such as the Universal Product Code (UPC) label establishes a plurality of counting gates based on a predetermined sequence of discrete signal transitions and counts a plurality of related pulse frequencies during the gating periods under control of the established counting gates. The accumulated counts are compared in a predetermined sequence to determine whether selected counts when compared bear a predetermined relationship to each other and a code generated indicative of the relationship which indicates the beginning of valid label data or invalid label data on a continuous basis.

Label find method and circuit

A circuit for filtering positive and negative glitches (i.e., dropouts and noise spikes) in a pulse-like signal to be processed, utilizes a single timing element which introduces a uniform delay in both the leading and trailing edges of the pulse-like signal, thus eliminating pulse-width distortion of the signal. A single adjustment may be made which has the same effect on both the leading and trailing edges making a uniform adjustment of both delays easily achieved.

Glitch filter circuit

A method and circuit for decoding coded electric signals from a scanner reading a coded label such as the Universal Product Code (UPC) label, establishes a plurality of counting gates based on a predetermined sequence of discrete signal transitions and counts a plurality of related pulse frequencies during the gating periods under control of the established counting gates. The counts are compared in a predetermined sequence to determine the relationship between their magnitudes (e.g., A &lt; B; A &gt; B) and a coded signal generated indicative of the relationship. The said coded signals indicate the value of the coded information.

Decoding method and circuit

A wand suitable for scanning the universal product code (UPC) symbol uses a light emitting diode for illuminating the symbol and a silicon photodetector for receiving the reflected energy. A single optical fiber is coupled to the diode and to a portion of a second single fiber for conducting narrow bandwidth visible light centered about 6,500 A to the terminus of the wand. The reflected light energy from the symbol when it is scanned by the wand is transmitted to the silicon photodetector via the said second single fiber which is also coupled to a third single fiber which conducts the reflected light energy to the silicon detector.

Growing community of inventors

Raleigh, NC, United States of America

George J Laurer