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					Barcode Reader
                           History
   The first barcode scanner was employed and the first product
    barcoded in 1974.
   In 1932 Wallace Flint started a project at the Harvard University
    Graduate School of Business Administration to better automate
    customer purchasing. As punch cards were all the rage at the
    time, the system they envisioned used a catalog of items with
    corresponding punch cards for each one. The customer would
    hand the cards to a clerk who would load them into a reader.
    The item would then be found and retrieved from a fully
    automated warehouse.An itemized bill was automatically
    produced. In spite of its promise, punch card systems were
    expensive.
   During the 40’s, 50’s and 60’s several code formats
    were developed .
   In america,1966 the National Association of Food
    Chains (NAFC) held a meeting where they
    discussed the idea of using automated checkout
    systems.
   On 3 April 1973 the IBM UPC code was selected
    by NAFC as their standard. NCR(national cash
    register) installed a testbed system at a Marsh
    supermarket in Troy, Ohio .
              Types of Barcode
   A bar code (also barcode) is an optical
    machine-readable representation of data.
    Originally, bar codes represented data in the
    widths (lines) and the spacings of parallel lines
    and may be referred to as linear or 1D (1
    dimensional) barcodes or symbologies. But they
    also come in patterns of squares, dots, hexagons
    and other geometric patterns within images
    termed 2D (2 dimensional) matrix codes or
    symbologies.
          1-D Barcode

Name           Use
UPC            Worldwide retail

Code128        Shipping company

EAN            Magazines , Books
2-D Barcode
     PDF417


     Data Matrix



     Maxi Code


     Aztec Code
Name          Capacity

PDF417        2725 char

Data Matrix   3116 char

Maxi Code     138 char

Aztec Code    3750 char
                                  Accuracy
    In studies conducted by the University of Ohio, common bar code symbologies were
     tested to determine real life accuracy. The worst bar code for data accuracy in the test
     proved to be one of the most common - the UPC. The UPC had a worst-case error
     rate of 1 error in 394K characters. The best-tested symbologies were the DataMatrix
     and PDF417, with a worst case error rate of 1 error in 10.5M characters. All the results
     from the University of Ohio study are listed below.

    Name                         Worst Case                    Best Case
    Data Matrix                  1 error in 10.5M              1 error in 612.9M
    PDF417                       1 error in 10.5M              1 error in 612.4M
    Code 128                     1 error in 2.8M               1 error in 37M
    UPC                          1 error in 394K               1 error in 800K
                Process of Reading



   The photo diode measures the intensity of the light reflected
    back from the light source and generates a waveform that is used
    to measure the widths of the bars and spaces in the bar code.
    Dark bars in the bar code absorb light and white spaces reflect
    light so that the voltage waveform generated by the photo diode
    is an exact duplicate of the bar and space pattern in the bar code.
    This waveform is decoded by the scanner .
    Types of Barcode Reader
 Pen type reader
 Laser scanner

 CCD reader

 Camera based reader
                Pen type reader




   Pen type readers consist of a light source and a photo
    diode that are placed next to each other in the tip of a
    pen . To read a bar code, you drag the tip of the pen
    across all the bars . The photo diode measures the
    intensity of the light reflected back from the light source
    and generates a waveform .
                                Laser Scanner




   Laser scanners work the same way as pen type readers except that they use a laser beam as the light source
    and typically employ on rotating prism to scan the laser beam back and forth across the bar code. Just the
    same as with the pen type reader, a photo diode is used to measure the intensity of the light reflected back
    from the bar code. In both pen readers and laser scanners, the light emitted by the reader is tuned to a
    specific frequency and the photo diode is designed to detect only this same frequency light.
CCD Reader
        CCD (Charge Coupled
         Device) readers use an array
         of hundreds of tiny light
         sensors lined up in a row in
         the head of the reader. Each
         sensor can be thought of as a
         single photo diode that
         measures the intensity of the
         light immediately in front of
         it. Each individual light
         sensor in the CCD reader is
         extremely small and because
         there are hundreds of sensors
         lined up in a row.
           Camera based Reader
   The fourth and newest type of bar code reader
    currently available are camera-based readers that use a
    small video camera to capture an image of a bar code.
    The reader then uses sophisticated digital image
    processing techniques to decode the bar code. Video
    cameras use the same CCD technology as in a CCD bar
    code reader except that instead of having a single row
    of sensors, a video camera has hundreds of rows of
    sensors arranged in a two dimensional array so that they
    can generate an image.
        Interface with Computer
   Keyboard wedge
   RS-232 port
   Wireless connection
                    Keyboard Wedge




   The bar code readers with keyboard wedge output plug directly into the keyboard port
    on your PC and they also provide a pigtail connector so that you can plug in your
    keyboard at the same time. When you scan a bar code with the keyboard wedge bar
    code reader, the data goes into the computer just as if it were typed in on the
    keyboard. This makes it extremely easy to interface the bar code reader to any
    application that is written to accept keyboard data.
RS-232 Port
         With these types of bar code
          readers, you connect the
          reader to an available serial
          port on the back of your PC.
          You would then need a
          program called a "Software
          Wedge" to take the data from
          the bar code reader and feed
          it to the application where
          you want the data to go.
           Wireless Connection
   Modern handheld barcode readers are operated
    in wireless networks according to WLAN or
    Bluetooth. However, such configuration limits
    the time of operation from battery or
    rechargeable battery and required recharging at
    least after a shift of operation.
                Barcode software
   Production software-to print bar codes on labels,
    documents, tickets, etc. or generate bar codes in
    Windows applications or on the Internet.
   Database & Inventory control software-to store data
    from my bar codes in my computer for inventory and
    other purposes. I need to look up recorded data, add,
    remove and change items, print recorded data and
    manipulate the saved data in various ways.
Thank you

				
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posted:11/10/2010
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