Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2003-06-25
2004-11-16
Frech, Karl D. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462470, C235S462430, C235S462450, C235S462360
Reexamination Certificate
active
06817529
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to optical scanners for bar code reading and in particular to the mechanical structure and ergonomics of a hand-held bar code reader.
2. Description of the Related Art
Various optical scanning systems and readers 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 graphic 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 function by electro-optically transforming the spatial pattern represented by the graphic indicia into a time-varying electrical signal, which is in turn decoded into data which represent the information or characters encoded in the indicia that are intended to be descriptive of the article or some characteristic thereof. Such data is typically represented in digital form and utilized as an input to a data processing system for applications in point-of-sale processing, inventory control, distribution, transportation and logistics, and the like. Scanning systems and readers 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; 5,015,833; 5,262,627; 5,504,316; 5,625,483; and 6,123,265, all of which have been assigned to the same assignee as the instant application and each of which is hereby incorporated by reference herein. 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 device supported by a user, which is configured to allow the user to aim a scanning head of the device, and more particularly, a light beam, at a targeted symbol to be read. U.S. Pat. No. 6,123,265 discloses resilient supports for defining a resting surface for the device.
The light source in a laser scanner bar code reader is typically a semiconductor laser. The use of semiconductor devices as the light source is especially desirable because of their small size, low cost and low voltage requirements. The laser beam is optically modified, typically by an optical assembly, to form a beam spot of a certain size at the target distance. It is often preferred that the cross-section of the beam spot measured in the scanning direction at the target distance be approximately the same as the minimum width in the scanning direction between regions of different light reflectivity, i.e., the bars and spaces of the symbol. Although typical readers utilize a single laser source, other bar code readers have been proposed with two or more light sources of different characteristics, e.g., different frequencies.
In the laser beam scanning systems known in the art, a single laser light beam is directed by a lens or other optical components along a light path toward a target that includes a bar code symbol on the target 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 across the pattern of the symbol, or scan the field of view of the scanner, or do both. The laser beam may be moved by optical or opto-mechanical means to produce a scanning light beam. Such action may be performed by either deflecting the beam (such as by a moving optical element, such as a mirror) or moving the light source itself. U.S. Pat. No. 5,486,944 describes a scanning module in which a mirror is mounted on a flex element for reciprocal oscillation by electromagnetic actuation. U.S. Pat. No. 5,144,120 to Krichever et al. describes laser, optical and sensor components mounted on a drive for repetitive reciprocating motion either about an axis or in a plane to effect scanning of the laser beam.
Another type of bar code scanner employs electronic means for causing the light beam to be deflected and thereby scan a bar code symbol, rather than using a mechanical motion to move or deflect the beam. For example, a linear array of closely spaced light sources activated one at a time in a regular sequence may be transmitted to the bar code symbol to simulate a scanned beam for a single source. Instead of a single linear array of light sources, a multiple-line array may also be employed, producing multiple scan lines. Such type of bar code reader is disclosed in U.S. Pat. No. 5,258,605 to Metlitsky et al.
Bar code reading systems also include a sensor or photodetector which detects 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, detected, and converted into an electrical signal.
In retroreflective light collection, a single optical component, e.g., a reciprocally oscillatory mirror, such as described in U.S. Pat. No. 4,816,661 or U.S. Pat. No. 4,409,470, both herein incorporated by reference, and Ser. No. 08/727,944, filed Oct. 9, 1996, scans the beam across a target surface and directs the collected light to a detector. The mirror surface usually is relatively large to receive as much incoming light as is possible, only a small detector being required since the mirror can focus the light onto a small detector surface, which increases signal-to-noise ratio.
Of course, small scan elements are preferable because of the reduced energy consumption and increased frequency response. When the scan element becomes sufficiently small, however, the area of the scanning mirror can no longer be used as the aperture for the received light. One solution is to use a staring detection system (a non-retroreflective system) which receives a light signal from the entire field which the scanned laser spot covers.
In non-retroreflective light collection, the reflected laser light is not collected by the same optical component used for scanning. Instead, the detector is independent of the scanning beam, and is typically constructed to have a large field of view so that the reflected laser light traces across the surface of the detector. Because the scanning optical component, such as a rotating mirror, need only handle the outgoing light beam, it can be made much smaller. On the other hand, the detector must be relatively large in order to receive the incoming light beam from all locations in the scanned field.
Electronic circuitry and 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 generated by the photodetector may be converted by a digitizer into a pulse width modulated digitized signal, with the widths corresponding to the physical widths of the bars and spaces. Alternatively, the analog electrical signal may be processed directly by a software decoder. See, for example, U.S. Pat. No. 5,504,318.
The decoding process of bar code reading systems usually works in the following way. The analog signal from the sensor or photodectector may initially be filtered and processed by circuitry and/or software. The pulse width modulated digitized signal is applied to a software algorithm, which attempts to decode the signal. 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 audible beep) is provided to the user. Otherwise, the decoder receives the next scan, and performs another decode according to a symbology specification into a binary representation of the data encoded in the symbol, and to the alphanumeric characters so represented.
The binary data is communicated
Barkan Edward
Drzymala Mark
Li Yajun
Frech Karl D.
Kirschstein et al.
Symbol Technologies Inc.
Walsh Daniel
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