Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
1999-09-13
2003-02-04
Lee, Michael G. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462010
Reexamination Certificate
active
06513714
ABSTRACT:
COPYRIGHT NOTICE/AUTHORIZATION
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
COMPUTER PROGRAM LISTING APPENDIX
This application includes a computer program listing appendix on a single compact disc, the contents of which are herein incorporated by reference. The compact disc contains a single 318KB file entitled 09-394986, created on Nov. 9, 2001.
FIELD OF THE INVENTION
The field of the present invention relates to data reading devices and, in particular, to optical code scanners or other label scanning and decoding systems of the type that are designed to read labels having information which may be presented in any one of a number of different codes commonly in use. More particularly, it relates to a system and methodologies for reconstructing complete bar code label information from partial scan information obtained under of variety of non-ideal situations.
BACKGROUND OF THE INVENTION
Existing labels encode information in a variety of formats and are commonly employed in applications such as inventory control systems and, most familiarly, affixed to consumer goods for retail store check-out, among others. Typically, the information encoded on each label uniquely identifies the product or product line. Such information, once decoded, can be used to identify other information, e.g., price, associated with the labeled object.
Optical scanning systems use various apparatus and methods for the purpose of reading such labels, identifying the particular label format, and decoding the information stored in the label. In the case of bar code scanners, for example, a typical system has one or more light sources, such as a laser or laser diode, which are used to scan the label. Traditional labels are ordinarily composed of a series of parallel dark and light areas, e.g., bars and spaces. A collection subsystem detects at least a portion of the light reflected from the label, distinguishes between dark and light areas, and converts the optical information into an electrical signal that can be recognized by a computer or other electronic system.
Labels, e.g., bar codes or other such symbols, commonly include characters (which can, e.g., be alphanumeric) defined by a number of elements, e.g., bars and spaces. For any given symbology, individual characters within a label are comprised of a given number of elements, and the width of each of these elements is expected to be within a known range, thus allowing the character to be reliably decoded. Exemplary of this is the Universal Product Code (UPC) label in which each character is made up of two bars and two interleaved spaces. The width of each character is measured in units called “modules” with each character being seven modules in width. The width of any particular bar or space within the character representation is between one and four modules. The character value depends on the relative width in modules of the two bars and two spaces it comprises. For example, indicating bars with a 1 and spaces with a 0, a sequence of 111 would represent a bar that is three modules in width.
If either of the above characteristics is violated (i.e., number of elements per character and/or width of elements in known range), typically the character in question will be considered to be undecodable and the entire scan of data will be discarded. Factors that could cause this are: if an individual element has been split into multiple pieces; multiple elements have been merged into a single piece; or, if the width of an element has been distorted beyond specified boundaries. In any of these instances, some existing systems may require a new scan—discarding the entire scan as unusable—even though only one character may be affected by the degradation.
Some codes make use of parity formats to form alternative representations for the digits 0 through 9. These alternate formats may be utilized in different locations on a label thus providing means for verifying accuracy of data. For example, UPC labels, with the exception of UPC-E labels, are comprised of right and left segment halves. Characters in the left segment are of odd parity and, when scanned from left to right, all begin with spaces. Characters in the right segment are of even parity and, when scanned from left to right, all begin with bars. Thus, the character value 5 may be represented as 0110001 using odd parity or 1001110 using even parity. Likewise, the character 3 may be represented as 0111101 using odd parity or 1000010 using even parity.
Additionally, many labels utilize feature characters, such as center or guard characters, as delimiters or to separate segments of the label. Most UPC labels, as noted above, have left and right segment halves. These segment halves are separated by a center band character that typically comprises two single module bars and three interleaved single module spaces. The beginning and end of the label are delimited by a pair of guard characters, each of which typically comprises two single module bars and one interleaved, single module space. The bar/space representations of these feature characters are unique from that of data characters to enhance detection and decoding capability. Furthermore, an unprinted margin area or white space is typically located outwardly of the two guard characters.
In addition to the UPC formats, a variety of other label formats exist which vary, among other ways, in structure, content, parity requirements, and type of feature characters. Code 39 and Code 128, for example, are both non-segmented label formats, i.e., they have no center feature characters separating two or more segments of bars. Other label encoding schemes have been developed which have differing pattern structures for the dark and light areas. Exemplary of these latter code types are the stacked bar code formats referred to as Code 49 and PDF 417.
As a practical matter, recovering information from optical code labels poses many difficulties that must be overcome by a scanning system. For example, in order to read a label completely, i.e., from left guard character or margin to right guard character or margin, in a single optical pass, the label must be properly oriented with respect to the scanning beam. Failure to read in a single pass, e.g., when a label is mis-framed or read diagonally across a top or bottom border, results in the reading of incomplete or degraded character data and yields partial scans of the label which must be assembled properly in order to formulate valid label information, otherwise the object must be re-positioned and re-scanned until a successful read is obtained. In such cases, data on either end of an input string may be inaccurately read, yet may appear to be an otherwise structurally valid character.
Even where a single optical pass does traverse the entire label from left to right, problems in decoding the label may occur, for example, when the label is folded, split, torn or similarly damaged, thus making it difficult to recover label information. Likewise, differences in package configurations, label sizes and locations, and scanner positions, among other factors, serve to exacerbate these problems. As a result, partially read labels are both more likely to occur and more difficult to decipher. In many applications, such as store check-out stands, this translates to a need for high operator concentration and dexterity yet results in non-optimum speed or efficiency, since the operator must take care to ensure that the object to be scanned is properly positioned (or must reposition and rescan repeatedly for a valid reading). As well, the multitude of optical code formats currently in use may require differing methodologies to be used in order to realize ideal (i.e., optimum speed and efficiency) decoding. In settings where
Brandt Jonathan R.
Davis Glen W.
Franklin Jamara A.
Lee Michael G.
PSC Scanning Inc.
Stoel Rives LLP
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