Registers – Coded record sensors – Readout control
Patent
1989-06-06
1992-01-14
Trafton, David
Registers
Coded record sensors
Readout control
235440, 235462, 341 61, G06K 700
Patent
active
050813420
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates generally to the processing of bar code data received from scanning devices, and more particularly to the processing of input data from various types of scanners reading a wide variety of bar codes and other digital data.
BACKGROUND ART
As is known, several types of scanning devices for reading bar codes are presently available. These include slot scanners in extensive use in supermarkets and other type of retail outlets, hand held scanners and light pen scanners. The data from these scanners must be processed to enable the information to be decoded by data processors and other types of equipment.
Bar codes comprise bar and space symbols, with the identification of whether each symbol is a bar or a space and the width of each bar or space (i.e., the interval between a bar-to-space or space-to-bar transition and the next transition) providing the information content of the code, e.g., the alpha
umerics which the code represents.
The printed bar code is first scanned by the beam of a light emitting device, i.e , laser, light emitting diode, etc. The light beam may be swept automatically across the code, as is the case with slot scanners or hand-held scanners or may be manually swept across the code, as is the case with light pens or wands. In either case, the scanning device includes light responsive components, such as photocells, to detect the light beam reflected off of the code. The light responsive means produce electrical signals corresponding to sensed symbols of the code. These signals are then processed and decoded.
Processing the bar code consists essentially of first detecting the occurrence of a bar-to-space transition or a space-to-bar transition, and then determining the interval between the transition and the next transition. A high frequency source is used to generate a series of pulses which are counted, and the total count determines the interval between the transitions (i.e., the width of the bar or space detected by the scanner). The digital counts representing the interval between transitions and the "sign" of the interval (i.e., whether the interval represents a bar or a space symbol) are then sent to a decoding device which converts the information to the original numerical and/or alphabetic representation of the bar code which has been read.
For processing the data from a slot or counter top scanner an internal frequency of forty megahertz (40 MHz) or twenty megahertz (20 MHz) is required. Occasionally a frequency as low as 10 MHz is most efficient. Processing of hand held scanner data is usually performed using frequencies of 5 or 2.5 MHz with 1.25 MHz occasionally used. For a light pen much lower frequencies are employed, ranging from an average of approximately 78 KiloHertz (KHz) down to 9.76 KHz.
Various types of bar codes are presently in use. The most commonly used bar code is the Universal Product Code, referred to as UPC. UPC is a universal code of the strictly numerical type and is in prevalent use for retailing purposes. Other codes include: (1) "EAN" which is the European equivalent of the UPC.; (2) "Code 39" which is an alpha-numeric bar code which is machine readable and is standard with the federal government for warehousing and inventory purposes; (3) The "I 2 of 5" code which is an interleaved numeric code and; (4) "Codabar" which is an early version of a numeric code with a limited number of other symbols, such as dollar sign, dash, etc. used mostly in the photo-processing field and for library codes.
Other codes which are highly specialized and not in prevalant use are the "Code 128" which includes a complete ASCII set and the "Plessey" code, "Code 93", and "Code 11".
As will be appreciated by those skilled in the art, bar code spacing can also vary, depending on the type of material the bar code is placed upon. For example, with a rough material, such as cardboard, the printing of the code is low density, that is, the bars and spaces are relatively wide. Such low density codes tend to decrease the frequency of detec
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Knowles C. Harry
Kolis George
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