Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2000-06-27
2003-08-19
Frech, Karl D. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462440, C235S462460
Reexamination Certificate
active
06607134
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to a portable electro-optical reader in a system for reading indicia of varying light reflectivity and, in particular, to a compact bar code symbol reader mounted on an index finger of a user such that the natural pointing direction of the index finger aims the reader and, more particularly, to a finger-mounted reader that communicates with other system components by a low power, wireless, radio frequency, communications protocol.
2. Description of the Related Art
Various electro-optical readers and systems have been developed heretofore for reading indicia such as bar code symbols appearing on a label or on a surface of an article. In its simplest form, the symbol itself is a coded pattern of indicia comprised of, for example, 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 scanning of bar code patterns has become more complex as bar code patterns have become both more complex and more compact. The typical bar code pattern includes lines and spaces of different widths extending in an x direction, and can be scanned by one or more linear scans in the x direction. Moreover, because the direction of the scan is not always precisely aligned with the direction of the bar code pattern, more complex omnidirectional scanning patterns are sometimes used, wherein consecutive scan lines are angularly displaced relative to one another to form a complex omnidirectional scanning pattern. Two dimensional (2D) bar code patterns (Code 49) have also been introduced wherein, in addition to a typical bar code pattern having lines and spaces of varying widths along an x direction, typical bar code patterns are stacked one upon the other in the y direction to form the 2D bar code pattern. Accordingly, scanning of a 2D bar code pattern is more complex, and requires a raster type of scan wherein consecutive x direction scans are displaced in the y direction by the spacing between stacked rows of the 2D bar code pattern to form a raster scan.
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; and 4,896,026, all of which have been commonly assigned to the same assignee as the present application.
As disclosed in some of the above patents, one embodiment of such a scanning system resides, inter alia, in a portable laser scanner which is grasped and hand-held by a user, which is designed to allow the user to aim the scanner, and more particularly, a light beam emanating therefrom, at a target bar code symbol to be read.
In prior art bar code scanners, the light source in a laser scanner is typically a gas laser or semiconductor laser. The use of a semiconductor device such as a laser diode as the light source in scanning systems is especially desirable because of its small size, low cost and low power requirements. The laser beam is optically modified, typically by a lens, to form a beam spot of a certain size at the target distance. It is preferred that the beam spot size 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.
Bar code symbols are formed from bars or elements that are 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.
For the purpose of this 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 hereby incorporated by reference.
A one-dimensional single-line scan, as ordinarily provided by hand-held readers, has disadvantages in reading these two-dimensional bar codes; that is, the reader must be aimed at each row individually. Likewise, the multiple-scan-line readers produce a number of scan lines at an angle to one another so these are not suitable for recognizing a Code 49 type of two-dimensional symbols.
In the scanning systems known in the prior art, the light beam is directed by a lens or similar optical components along a light path toward a target that includes a bar code symbol on the surface. The scanning functions by repetitively scanning the light beam in a line or series of lines across the symbol. The scanning component may either sweep the beam spot across the symbol and trace a scan line across and past the symbol, or scan the field of view of the scanner, or both.
Scanning systems also include a sensor or photodetector which functions to detect light reflected from the symbol. The photodetector is therefore positioned in the scanner or in an optical path in which it has a field of view which extends across and slightly past the symbol. A portion of the reflected light which is reflected by the symbol is detected and converted into an electrical signal, and electronic circuitry or software decodes the electrical signal into a digital representation of the data represented by the symbol that has been scanned. For example, the analog electrical signal from the photodetector may typically be converted into a pulse width modulated digital signal, with the widths corresponding to the physical widths of the bars and spaces. 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 represented thereby.
The decoding process in known scanning system usually works in the following manner. The decoder receives the pulse width modulated digital signal from the scanner, 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 are 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 s
Bard Simon
Hamilton Alistair R.
Maiman Mitchell H.
Swartz Jerome
White Jay Paul
Frech Karl D.
Kirschstein et al.
Symbol Technologies Inc.
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