DETECTOR FOR READING BAR CODES ON MOVING ARTICLES AND HAVING IMPROVED SIGNAL-TO-NOISE RATIO

• US 3,745,354 A
• Filed: 04/23/1971
• Issued: 07/10/1973
• Est. Priority Date: 04/23/1971
• Status: Expired due to Term

• Current Assignee: Donald P. Vargo
• Original Assignee: Donald P. Vargo
• Inventors: Vargo, Donald P.
• Primary Examiner(s): Stolwein, Walter
• Application Number:
  US05/136,769
• Time in Patent Office: 809 Days
• Field of Search: 250/219D,219DC,219DD,208,209 333/70 235/61.11E
• US Class Current: 235/462.02
• CPC Class Codes: B65G 47/49 without bodily contact between article or load carrier and automatic control device , e.g. the destination marks being electrically or electronically detected
• CPC Class Codes: G06K 2207/1012 Special detection of object
• CPC Class Codes: G06K 7/10861 sensing of data fields affixed to objects or articles, e.g. coded labels postal sorting B07C3/14, conveying articles B65G47/48

Abstract

A detection system is provided of the type used for reading bar coded indicia on articles passing on a moving conveyor and for emitting a corresponding output signal to be used in subsequently manipulating the articles. To reduce noise in the output signal and so to provide an improved signal-to-noise ratio and more accurate manipulation of the articles in response to the code, the detection system is arranged to be selectively responsive not only to the frequency characteristic of the spacing of the coded bars, relative to their speed of passage, but also similarly responsive to the frequency characteristic of the width of the bars in the code. This predetermined detection frequency is established in the coded indicia by giving each individual bar a uniform width dimension, preferably equal to the spacing between adjacent bars. The detector includes a notch filter passing this predetermined frequency so that wide band noise and spurious signals developed at other frequencies will be eliminated from the output signal.

Claims

1. Detection apparatus for detecting the presence or absence of information in data code bar positions aligned with clock bars adjacent thereto, both data and clock bars appearing on articles moving at uniform speed relative to the detection apparatus and being formed with predetermined uniform widths, and having uniform spaces between bars equal to said uniform widths, thereby providing for every clock and data bar a predetermined detection frequency related to the speed at which the bars are scanned, the detection apparatus comprising:

first scanning means for scanning across the data bars to thereby retrieve the data of said bars and to produce data signals corresponding to the presence of said bars and having said predetermined frequency;

second scanning means for scanning across the clock bars synchronously with the scanning of said first scanning means and to produce clock signals as each data bar position is scanned, said clock signals having said predetermined frequency;

first bandpass filter means receiving said data signals and passing essentially only said predetermined frequency;

second bandpass filter means receiving said clock signals and passing essentially only said predetermined frequency;

said first and second bandpass filter means being notch filters with a Q of 1; and

coincidence means for comparing signals from said first and second filter means.

2. Apparatus as defined in claim 1 wherein said clock and data bars are a luminescent material and said apparatus includes means for irradiating said bars with ultraviolet light.

3. In a method for detecting the presence or absence of information in the data code bar positions aligned with clock code bars adjacent thereto, both clock and data bars being found on articles moving past a dual detector at uniform speed, wherein the dual detector simultaneously scans across the clock bars and data bars to retrieve the information of the data bars and, through associated circuitry, transmits said data for control or accounting purposes, the improvement which comprises:

forming said clock bars and data bars with a predetermined uniform width, the space between said clock bars being uniform and equal to said predetermined width thereby providing for every bar a predetermined detection frequency related to the speed at which said detector scans across a bar;

scanning across said data bars to produce a data signal corresponding to the presence of said data bars and having said predetermined frequency;

simultaneously scanning across said clock bars to produce a clock signal having said predetermined frequency;

separately filtering said data and clock signals simultaneously, with sharply defined bandpass filters having a Q of 1, passing essentially only signals of said predetermined detection frequency;

whereby an improved signal to noise ratio results and sensitivity of detection is increased for each signal; and

comparing said filtered data and clock signals in coincidence means.

4. ThE method of claim 3 wherein said clock and data bars are formed from luminescent material and said bars are irradiated with ultraviolet light during scanning.