Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2002-04-11
2004-03-23
Le, Thien M. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462250, C235S455000
Reexamination Certificate
active
06708883
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to an apparatus and method operative for electro-optically reading indicia having parts of different light reflectivity, for example, bar code or matrix array symbols, and, more particularly, to apparatus using both charge coupled device (CCD) technology and laser beam scanning technology for properly positioning, orienting and/or aiming such apparatus and reading one or two-dimensional bar code symbols, and to a method therefor.
2. Description of the Related Art
Various optical readers and optical scanning systems have been developed heretofore for reading indicia such as bar code symbols appearing on a label or on the surface of an article. The bar code symbol itself is a coded pattern of indicia comprised of a series of bars of various widths spaced apart from one another to bound spaces of various widths, the bars and spaces having different light-reflecting characteristics. The readers and scanning systems electro-optically transform the graphic indicia into electrical signals, which are decoded into alphanumerical characters that are intended to be descriptive of the article or some characteristic thereof. Such characters are typically represented in digital form and utilized as an input to a data processing system for applications in point-of-sale processing, inventory control, and the like. Scanning systems of this general type have been disclosed, for example, in U.S. Pat. Nos. 4,251,798; 4,369,361; 4,387,297; 4,409,470; 4,760,248; 4,896,026, all of which have been assigned to the same assignee as the instant application.
As disclosed in some of the above patents, one embodiment of such a scanning system resides, inter alia, in a hand-held, portable laser scanning head supported by a user, which is configured to allow the user to aim the head, and more particularly, a light beam, at a target and a symbol to be read.
The light source in a laser scanner bar code reader is typically a gas laser or semiconductor laser. The use of semiconductor devices as the light source in scanning systems is especially desirable because of their small size, low cost and low voltage requirements. The laser beam is optically modified, typically by a focusing optical assembly, to form a beam spot of a certain size at the target distance. It is preferred that the cross section of the beam spot at the target distance be approximately the same as the minimum width between regions of different light reflectivity, i.e., the bars and spaces of the symbol.
The bar code symbols are formed from bars or elements typically rectangular in shape with a variety of possible widths. The specific arrangement of elements defines the character represented according to a set of rules and definitions specified by the code or “symbology” used. The relative size of the bars and spaces is determined by the type of coding used, as is the actual size of the bars and spaces. The number of characters per inch represented by the bar code symbol is referred to as the density of the symbol. To encode a desired sequence of characters, a collection of element arrangements are concatenated together to form the complete bar code symbol, with each character of the message being represented by its own corresponding group of elements. In some symbologies, a unique “start” and “stop” character is used to indicate where the bar code begins and ends. A number of different bar code symbologies exist. These symbologies include UPC/EAN, Code 39, Code 128, Codabar, and Interleaved 2 of 5, etc.
For the purpose of our discussion, characters recognized and defined by a symbology shall be referred to as legitimate characters, while characters not recognized and defined by that symbology are referred to as illegitimate characters. Thus, an arrangement of elements not decodable by a given symbology corresponds to an illegitimate character(s) for that symbology.
In order to increase the amount of data that can be represented or stored on a given amount of surface area, several new bar code symbologies have recently been developed. One of these new code standards, Code 49, introduces a “two-dimensional” concept by stacking rows of characters vertically instead of extending the bars horizontally. That is, there are several rows of bar and space patterns, instead of only one row. The structure of Code 49 is described in U.S. Pat. No. 4,794,239, which is incorporated herein by reference. Another two-dimensional symbology, known as “PDF417”, is described in U.S. patent application Ser. No. 461,881, now U.S. Pat. No. 5,304,786. Still other symbologies have been developed in which the symbol is comprised of a matrix array made up of hexagonal, square, polygonal and/or other geometric shapes. Prior art
FIGS. 24A-24C
depict exemplary known matrix and other type symbols. Such symbols are further described in, for example, U.S. Pat. Nos. 5,276,315 and 4,794,239. Such matrix symbols may include Vericode(TM), Datacode(TM) and UPSCODE(TM).
In the laser beam scanning systems known in the art, the laser light beam is directed by a lens or similar optical components along a light path toward a target that includes a bar code or other symbol on the surface. The moving-beam scanner operates by repetitively scanning the light beam in a line or series of lines across the symbol by means of motion of a scanning component, such as the light source itself or a mirror, disposed in the path of the light beam. The scanning component may either sweep the beam spot across the symbol and trace a scan line or pattern across the symbol, or scan the field of view of the scanner, or do both.
Bar code reading systems also include a sensor or photodetector which functions to detect light reflected or scattered from the symbol. The photodetector or sensor is positioned in the scanner in an optical path so that it has a field of view which ensures the capture of a portion of the light which is reflected or scattered off the symbol is detected and converted into an electrical signal. Electronic circuitry or software decode the electrical signal into a digital representation of the data represented by the symbol that has been scanned. For example, the analog electrical signal operated by the photodetector may be converted into a pulse width modulated digital signal, with the widths corresponding to the physical widths of the bars and spaces. Such a digitized signal is then decoded based upon the specific symbology used by the symbol into a binary representation of the data encoded in the symbol, and subsequently to the alphanumeric characters so represented.
The decoding process in known bar code reading systems usually works in the following way The decoder receives the pulse width modulated digital signal from the bar code reader, and an algorithm implemented in software attempts to decode the scan. If the start and stop characters and the characters between them in the scan were decoded successfully and completely, the decoding process terminates and an indicator of a successful read (such as a green light and/or an audible beep) is provided to the user. Otherwise, the decoder receives the next scan, performs another decode attempt on that scan, and so on, until a completely decoded scan is achieved or no more scans are available.
Such a signal is then decoded according to the specific symbology into a binary representation of the data encoded in the symbol, and to the alphanumeric characters so represented.
Moving-beam laser scanners are not the only type of optical instrument capable of reading bar code symbols. Another type of bar code reader particularly relevant to the present invention is one which incorporates detectors based upon charge coupled device (CCD) technology. In such prior art readers the size of the detector is typically smaller than the symbol to be read because of the image reduction by the objective lens in front of the CCD. The entire symbol is flooded with light from a light source such as light emitting diodes (LED) in the reader, and each CCD cell is sequentially
Kirschstein et al.
Le Thien M.
Symbol Technologies Inc.
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