Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2001-03-02
2002-11-12
Le, Thien M. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462160, C235S462180
Reexamination Certificate
active
06478224
ABSTRACT:
BACKGROUND OF THE INVENTION
Labels bearing information in any of a number of different bar code formats are commonly affixed to products, packaging, or other items and are used in many applications. It is common, for example, to encode retail product identification information in a bar code format on a product package or a label affixed to a product package. Bar code symbols are also used on a broad range of retail packages for check-out and inventory purposes. A bar code reader, located at the check-out station of a retail establishment for example, may be used by a clerk to enter product identification data from a bar code label into an associated point-of-sale computer system.
Bar codes typically consist of a series of parallel light and dark rectangular areas of varying widths. The light areas are often referred to as “spaces” and the dark areas as “bars,” with the bars and spaces arranged and selected to define different characters of a particular bar code.
A bar code label is typically read by a bar code reader, such as a scanner, which illuminates the target containing the bar code label to be read and detects reflected and/or refracted light from the bars and spaces of the bar code. One common method of illuminating the target is by use of a scanning laser beam, in which case a spot of light is swept across the bar code label and the intensity of returned light is detected by a photodetector. The photodetector generates an electrical signal having an amplitude determined by the intensity of the detected light.
Another method for illuminating the target containing the bar code label and detecting return light is by use of a uniform light source and an array of optical detectors connected to an analog shift register (commonly called a charge-coupled device or CCD). Such a CCD imager can be a single line CCD array or else a two-dimensional CCD array. In such a technique, as with a scanning laser, an electrical signal is generated having an amplitude determined by the intensity of the collected light.
Alternately, the bar code reader may generate an electrical signal having an amplitude determined by the intensity of detected light without illuminating the target, as described, for example, in U.S. Pat. No. 6,073,851, which is assigned to the assignee of the present application and hereby incorporated by reference as if set forth fully herein.
In either the laser or CCD technique, the amplitude of the electrical detector signal has one level for dark bars and a second level for light spaces. A relatively large amplitude of the electrical signal indicates a high level of reflected and/or refracted light and, therefore, light areas of a target (such as white spaces of the bar code), while a relatively small amplitude of the electrical signal indicates a low level of reflected and/or refracted light and, therefore, dark areas of a target (such as bars of the bar code).
The widths of light areas and dark areas on the target are measured by signal processing circuitry. The electrical signal is indicative of the widths of dark areas and light areas of the scanned target. As a target is scanned, positive-going transitions and negative-going transitions in the electrical signal occur, signifying transitions between dark areas and light areas (such as bars and spaces). Various techniques for measuring the widths of light areas and dark areas on a target are described in, for example, U.S. Pat. No. 4,000,397 (Hebert et al.), U.S. Pat. No. 5,463,211 (Arends et al.) and U.S. Pat. No. 5,446,271 (Cherry et al.), and in copending patent application Ser. No. 09/658,300 entitled “Multi-format Optical Reader” (filed Sep. 8, 2000 as a continuation of application Ser. No. 09/118,228 filed Jul. 17, 1998), each of which is assigned to the assignee of the present application, and each of which is hereby incorporated by reference as if set forth fully herein.
A decoder attempts to decode the information contained in the electrical signal. Various techniques for reading and processing electrical bar code signals are described in, for example, U.S. Pat. Nos. 4,000,397, 5,463,211 and 5,446,271, each of which is referenced above and incorporated herein.
While the use of bar codes greatly enhances the efficiency of the check-out process in retail establishments and additionally allows the accumulation of sales or inventory data which is important for proper management control, difficulties may be encountered due to the amount of data from the electrical signal that must be processed.
For example, the bar code reader cannot predict where the bar code data will be on the product and therefore must scan any area in which the target bar code might be located. As a result, the bar code reader scans much more area than necessary to read the bar code, including parts of the product that do not contain the bar code. The bar code reader must therefore read and process far more information than the target bar code data. Moreover, this task is made more burdensome by the fact that a large amount of extraneous data resembling bar code data may need to be discriminated from the actual target bar code data.
Typically, the detector will detect light reflected from parts of the product packaging other than the bar code and will output an electrical signal indicative of light areas and dark areas of the packaging that do not represent a bar code. The light areas and dark areas might be found, for example, in text, graphics or other printing that are often found on packaging and which may produce an electrical signal resembling that produced by a bar code.
Because bar code readers typically must process the entire electrical signal, whether produced from the bar code or other areas of the target, to determine which parts represent bar code data, processing time and resources are typically wasted on reading and processing extraneous data. Given that the bar code typically occupies a small portion of a target, much of the electrical signal does not represent bar code data, but still must be processed to determine that fact. This increases the load on the decoder beyond the load that would exist if only bar code data were contained in the electrical signal.
To facilitate determination of what portion of the electrical signal constitutes bar code data, bar codes sometimes include “quiet zones” that border the outermost bars and spaces of the bar code and mark the location of the bar code. Typically, these quiet zones comprise a white area that is substantially wider than the widest bar or space of a particular bar code symbology. The quiet zones are theoretically designed so that they can be easily recognized by the bar code reader. The bar code reader can be programmed to disregard information that is not bounded by the quiet zone.
Quiet zones, however, are not always effective. Sometimes quiet zones are contaminated by dirt, smeared ink, or other particles, so that the bar code reader does not recognize the quiet zone, potentially preventing a successful scan. Other times, the bar code may be printed on the edge of a package, and some portion of the quiet zone may not be printed on the package, potentially preventing a successful scan.
Further, some bar code symbologies do not employ quiet zones at all. Bar code readers that rely on the existence of quiet zones may be unable to read such symbologies.
The difficulties arising from the large amount of data received from the detector may be exacerbated by the number of different bar code symbologies that may be in use. Because a bar code reader at a particular location may need to read bar codes in many different symbologies, the bar code reader circuitry in such a situation must be capable of recognizing and decoding bar codes printed according to any of a variety of symbologies used or expected in a particular application. This requirement presents substantial difficulties since bar codes in common usage vary significantly in their formats. These codes include, for example, Code 3 of 9, Interleaved 2 of 5 Code, Codabar, Code 93, Code 128, the Universal Product Code (UPC)
Le Thien M.
Le U Chau
Lyon & Lyon LLP
PSC Scanning Inc.
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