Latest News
Updated:
03/21/2003
Baracoda
to Present the First Range of Bluetooth Wireless Barcode Scanners at CeBIT
2003
Symbol
Handhelds Support LANs, WANs
Barcode Technology
Each character is represented by a pattern of wide and narrow bars. A barcode reader uses a photosensor to convert the barcode into an electrical signal as it moves across a barcode. The scanner then measures the relative widths of the bars and spaces, translates the different patterns back into regular characters and sends them on to a computer or portable terminal.
There are different barcode systems, each with its own particular pattern of bars. The UPC code used on retail products is an all-numeric code. Code 39 includes upper case letters, digits and a few symbols. Code 128 includes every printable and unprintable ASCII character code.
Two-Dimensional symbols are generally square or rectangular patterns that encode data in two dimensions. They fall into two general categories: Stacked Barcodes are constructed like a layer cake of barcodes stacked one on top of the other; they can be read by special 2-D scanners or by many CCD and laser scanners with the aid of special decoding software. Matrix Barcodes are built on a true 2-D matrix; they are usually more compact than a stacked barcode, and they can be read only by a true 2-D scanner. The primary advantage of 2-D codes is the ability to encode a lot of information in a small space.
The practical limit for a standard barcode depends on a
number of factors, but 20 to 25 characters is an approximate maximum;
2-D symbols can encode from 100 to about 2,000 characters. United Parcel
Service uses a 1-inch square label with a pattern of dots and a small
bullseye in the center. This is a MaxiCode
label, and it is used by UPS for automatic destination sorting. Two other
popular 2-D codes are PDF-417
and DataMatrix.
Scanning Technologies
LED
 |
A single light-emitting diode illuminates a small spot on the barcode and a photocell measures the amount of light reflected. As the LED moves across the barcode the pattern of bars and spaces is captured and decoded. Light is focused through a small transparent ball at the tip of a wand. The user just swipes the wand across the barcode to scan. The tip of the wand generally has to be in physical contact with the surface of the barcode. As long as the operator can sweep the scanner from one end of the barcode to the other at an even speed without wandering off the code, the maximum width of a barcode is theoretically unlimited.
CCD
 |
CCD stands for Charge-Coupled
Device; it refers to a single row of photocells on a single semiconductor
chip. Unlike a single photocell which can see only one spot on the barcode
at a time, a CCD can see a cross-section of the whole barcode at once.
The barcode is generally illuminated by a row of light-emitting diodes
built into the scanner. CCD scanners are also available with 2-dimensional
arrays; these scanners are like miniature electronic cameras and they
can capture a rectangular image. This type of scanner is often called
an Imager, and is used to read 2-dimensional barcodes like PDF-417,
DataMatrix
or Maxicode.
The target is generally illuminated with a group of light-emitting diodes.
CCD scanners do not have to be in direct contact with the surface of the
barcode, but their depth of focus is somewhat limited. Most CCD scanners
have a working range from roughly 0.25 inch to 1.0 inch. The width of
the CCD sensor array in the scanner limits the maximum width of a barcode
that can be scanned; if the barcode is wider than the scanner, it cannot
be read.
Laser
 |
Laser scanners use a moving pinpoint of light to illuminate the barcode, and a single photocell receives the reflected light. Most laser scanners sweep the laser beam horizontally using an electronically controlled mirror. Laser scanners tend to be quick and precise and can often read denser barcodes than other technologies. A primary advantage of a laser scanner is depth of focus; since a laser beam diverges very little with distance, scanners of this type generally have a working range from roughly 1 inch to 12 inches. By increasing laser power and narrowing the angle of beam sweep special long-range scanners can read at ranges as long as to 30 to 40 feet. Since the laser beam is swept horizontally at a fixed angle, the length of the scan line on the target increases as the distance increases; if a barcode is too wide for the laser beam, just back up a little bit. Two-dimensional laser scanners sweep the beam horizontally and vertically at the same time, creating a raster pattern. This type of scanner is used to read 2-dimensional barcodes like PDF-417.