Registers – Systems controlled by data bearing records
Reexamination Certificate
2002-06-03
2004-05-04
Le, Thien M. (Department: 2876)
Registers
Systems controlled by data bearing records
C235S462070, C235S462120, C235S470000
Reexamination Certificate
active
06729603
ABSTRACT:
BACKGROUND
The field of the present invention relates to data reading devices, such as barcode scanners and other barcode reading devices. In particular, barcode readers are described herein which employ methods whereby the capture rate of reading labels with add-ons is improved without sacrificing throughput with respect to non-add-on labels.
Barcode labels encode information in a variety of formats, i.e., symbologies, 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, may be used to identify other information, e.g., price, associated with the labeled object.
A barcode label typically comprises a series of parallel dark bars of varying widths with intervening fight spaces, also of varying widths. Character information (which can, e.g., be alpha-numeric) is encoded in the labels by the specific sequence of bars and spaces with groupings of bars and spaces representing the character information. The precise nature of the representation depends on the particular barcode symbology in use.
One traditional symbology 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. The character value 5 may be represented as 0110001, i.e., one space that is 1 module in width, one bar that is 2 modules in width, one space that is 3 modules in width, and one bar that is one module in width, respectively. Likewise, the character 3 may be represented as 0111101.
With respect to the UPC label symbology alone there are many variations, such as UPC-A, UPC-E, etc. With the exception of UPC-E labels, the UPC symbologies comprise right and left segment halves. 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. Furthermore, many new label encoding schemes have been developed which have differing pattern structures for the dark and light areas. Exemplary of these newer code types are the stacked bar code formats referred to as Code 49 and PDF 417.
As indicated previously, with respect to the traditional symbologies such as UPC, the character information encoded in the barcode is represented by the specific sequence of bar and space widths. In addition to data characters, 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 a further variation, a typical UPC/EAN barcode may or may not also include an additional piece of information in the form of a second, adjacent barcode called an “add-on” located beyond the white space margin beyond the end guard character.
Optical scanning systems and other data reading systems, e.g., barcode readers, use various devices and methods for the purpose of reading such labels, identifying the particular label format, and decoding the information stored in the label. Common types of barcode readers include spot scanners and line scanners. In either case, one or more light sources, such as a laser or laser diode, are utilized to scan the label with a collection subsystem detecting at least a portion of the light reflected from the label, distinguishing between dark and light areas, and converting the optical information into an electronic signal that may be recognized by a computer or other electronic system.
In spot scanners, a reading spot is systematically moved across the barcode, either manually or automatically. The resultant paths followed by the scanned illumination beam are typically referred to as a scan lines. A photodetector monitors the reflected or back-scattered light from each scan line. The photodetector may generate a high current when a large amount of light scattered from the barcode impinges on the detector, as from a light space, and likewise may produce a lower current when a small amount of light scattered from the barcode impinges on the photodetector, as from a dark bar.
With respect to line scanner systems, the barcode is focused onto a multi-element linear or areal photodetector array and the image of the barcode is detected. Though some imaging systems employ ambient light to illuminate the barcode, a light, source may also illuminate the barcode to provide the required signal response corresponding to the image. The imaging optics which produce an image of the barcode on the photodetector array can alternatively be thought of as projecting an image of the photodetector array (a “virtual scan line”) into the scan volume in a manner completely analogous to the real scan line produced by a spot scanner. Further, scan pattern generating optics may be used to project multiple virtual scan lines into the scan volume in various directions and at varying orientations, thereby generating a virtual scan pattern, once again completely analogous to the real scan pattern produced by a spot scanner. Such a virtual scan line system is disclosed in U.S. Pat. No. 5,446,271 hereby incorporated by reference.
Regardless of which type of barcode reader is used, a raw electronic signal is generated from which the relative widths of the bars and spaces must be extracted. The electronic signal that is generated typically comprises a signal wherein voltage alternates between two preset voltage levels, one representative of the dark bars and the other representative of the light spaces. The temporal widths of these alternating pulses of high and low voltage levels correspond to the spatial widths of the bars and spaces. High-to-low or low-to-high transitions in the electronic signal voltage, representing edges of the bars and spaces (i.e., elements) in the barcode, may be detected by any of a number of means well known in the art. A common and well-known technique for edge detection is through the use of a derivative based signal processor such as is described by example in U.S. Pat. No. 4,000,397 entitled “Signal Processor Method and Apparatus” issued in the name of Hebert et al. and owned by the owner of the present application, which patent is hereby incorporated by reference as if fully set forth herein. The temporal sequence of alternating voltage pulses of varying widths comprising the electronic signal is then presented to an electronic decoding apparatus for decoding of the information encoded in the barcode.
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 m
Cherry Craig D.
McQueen Alexander M.
Turkal Randy J.
Labaze Edwyn
Le Thien M.
PSC Scanning Inc.
Stoel Rives LLP
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