Barcode reader
Overview
 
A barcode reader is an electronic device for reading printed barcode
Barcode
A barcode is an optical machine-readable representation of data, which shows data about the object to which it attaches. Originally barcodes represented data by varying the widths and spacings of parallel lines, and may be referred to as linear or 1 dimensional . Later they evolved into rectangles,...

s. Like a flatbed scanner, it consists of a light source, a lens and a light sensor translating optical impulses into electrical ones. Additionally, nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the sensor and sending the barcode's content to the scanner's output port.
Pen-type readers consist of a light source and a photodiode
Photodiode
A photodiode is a type of photodetector capable of converting light into either current or voltage, depending upon the mode of operation.The common, traditional solar cell used to generateelectric solar power is a large area photodiode....

 that are placed next to each other in the tip of a pen or wand.
Encyclopedia
A barcode reader is an electronic device for reading printed barcode
Barcode
A barcode is an optical machine-readable representation of data, which shows data about the object to which it attaches. Originally barcodes represented data by varying the widths and spacings of parallel lines, and may be referred to as linear or 1 dimensional . Later they evolved into rectangles,...

s. Like a flatbed scanner, it consists of a light source, a lens and a light sensor translating optical impulses into electrical ones. Additionally, nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the sensor and sending the barcode's content to the scanner's output port.

Pen-type readers

Pen-type readers consist of a light source and a photodiode
Photodiode
A photodiode is a type of photodetector capable of converting light into either current or voltage, depending upon the mode of operation.The common, traditional solar cell used to generateelectric solar power is a large area photodiode....

 that are placed next to each other in the tip of a pen or wand. To read a bar code, the person holding the pen must move the tip of it across the bars at a relatively uniform speed. The photodiode measures the intensity of the light reflected back from the light source as the tip crosses each bar and space in the printed code. The photodiode 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 a representation of the bar and space pattern in the bar code. This waveform is decoded by the scanner in a manner similar to the way Morse code
Morse code
Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...

 dots and dashes are decoded.

Laser scanners

Laser scanners work the same way as pen type readers except that they use a laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

 beam as the light source and typically employ either a reciprocating mirror or a rotating prism to scan the laser beam back and forth across the bar code. As with the pen type reader, a photodiode 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 rapidly varied in brightness with a data pattern and the photodiode receive circuitry is designed to detect only signals with the same modulated
Modulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...

 pattern.

CCD readers

CCD
Charge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...

 readers use an array of hundreds of tiny light sensors lined up in a row in the head of the reader. Each sensor 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, a voltage pattern identical to the pattern in a bar code is generated in the reader by sequentially measuring the voltages across each sensor in the row. The important difference between a CCD reader and a pen or laser scanner is that the CCD reader is measuring emitted ambient light from the bar code whereas pen or laser scanners are measuring reflected light of a specific frequency originating from the scanner itself.

Camera-based readers

Two-dimensional imaging scanners
Machine vision
Machine vision is the process of applying a range of technologies and methods to provide imaging-based automatic inspection, process control and robot guidance in industrial applications. While the scope of MV is broad and a comprehensive definition is difficult to distil, a "generally accepted...

 are the fourth and newest type of bar code reader. They use a camera and image processing techniques to decode the bar code.

Video camera readers use small video cameras with 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.

Large field-of-view readers use high resolution industrial cameras to capture multiple bar codes simultaneously. All the bar codes appearing in the photo are decoded instantly (ImageID patents [htww.ashberg.de/php-barcode/ Folke Ashberg: EAN-13 Image-Scanning] and code creation tools) or by use of plugins (e.g. the Barcodepedia uses a flash application and some web cam for querying a database), have been realized options for resolving the given tasks.

Omni-directional barcode scanners

Omni-directional scanning uses "series of straight or curved scanning lines of varying directions in the form of a starburst, a lissajous pattern
Lissajous curve
In mathematics, a Lissajous curve , also known as Lissajous figure or Bowditch curve, is the graph of a system of parametric equationswhich describe complex harmonic motion...

, or other multiangle arrangement are projected at the symbol and one or more of them will be able to cross all of the symbol's bars and spaces, no matter what the orientation."

Omni-directional scanners almost all use a laser. Unlike the simpler single-line laser scanners, they produce a pattern of beams in varying orientations allowing them to read barcodes presented to it at different angles. Most of them use a single rotating polygonal mirror and an arrangement of several fixed mirrors to generate their complex scan patterns.

Omni-directional scanners are most familiar through the horizontal scanners in supermarkets, where packages are slid across a glass or sapphire window. There are a range of different omni-directional units available which can be used for differing scanning applications, ranging from retail type applications with the barcodes read only a few centimetres away from the scanner to industrial conveyor scanning where the unit can be a couple of metres away or more from the code. Omni-directional scanners are also better at reading poorly printed, wrinkled, or even torn barcodes.

Cell phone cameras

While cell phone cameras without auto-focus are not ideal for reading some common barcode formats, there are 2D barcodes which are optimized for cell phones, as well as QR Code
QR Code
A QR code is a type of matrix barcode first designed for the automotive industry. More recently, the system has become popular outside of the industry due to its fast readability and comparatively large storage capacity. The code consists of black modules arranged in a square pattern on a white...

s and Data Matrix codes which can be read quickly and accurately with or without auto-focus.
These open up a number of applications for consumers:
  • Movies: DVD/VHS movie catalogs
  • Music: CD catalogs, play MP3 when scanned
  • Book catalogs
  • Groceries, nutrition information, making shopping lists when the last of an item is used, etc.
  • Personal Property inventory (for insurance and other purposes)ode scanned into personal finance software when entering. Later, scanned receipt images can then be automatically associated with the appropriate entries. Later, the bar codes can be used to rapidly weed out paper copies not required to be retained for tax or asset inventory purposes.
  • If retailers put barcodes on receipts that allowed downloading an electronic copy or encoded the entire receipt in a 2D barcode, consumers could easily import data into personal finance, property inventory, and grocery management software. Receipts scanned on a scanner could be automatically identified and associated with the appropriate entries in finance ad property inventory software.
  • Consumer tracking from the retailer perspective (for example, loyalty card programs that track consumers purchases at the point of sale by having them scan a QR code).


A number of enterprise applications using cell phones are appearing:
  • Access control (for example, ticket validation at venues), inventory reporting (for example, tracking deliveries), asset tracking (for example, anti-counterfeiting).

Housing types

The reader packaging can be distinguished as follows :
Handheld scanner: with a handle and typically a trigger button for switching on the light source.
Pen scanner (or wand scanner): a pen-shaped scanner that is swiped.
Stationary scanner: wall- or table-mounted scanners that the barcode is passed under or beside. These are commonly found at the checkout counters of supermarket
Supermarket
A supermarket, a form of grocery store, is a self-service store offering a wide variety of food and household merchandise, organized into departments...

s and other retailers.
Fixed-position scanner: an industrial barcode reader used to identify products during manufacture or logistics. Often used on conveyor tracks to identify cartons or pallets which need to be routed to another process or shipping location. Another application joins holographic scanners with a checkweigher to read bar codes of any orientation or placement, and weighs the package. Systems like this are used in factory and farm automation for quality management
Quality management
The term Quality management has a specific meaning within many business sectors. This specific definition, which does not aim to assure 'good quality' by the more general definition , can be considered to have four main components: quality planning, quality control, quality assurance and quality...

 and shipping.
PDA scanner (or Auto-ID PDA): a PDA
Personal digital assistant
A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...

 with a built-in barcode reader or attached barcode scanner.
Automatic reader: a back office equipment to read barcoded documents at high speed (50,000/hour).
Cordless scanner (or Wireless scanner): a cordless barcode scanner is operated by a battery fitted inside it and is not connected to the electricity mains

Symbology Decoding Algorithm

The Symbology Decoding Algorithm for barcode scanners is the first symbology-based algorithm for decoding. The new technique utilizes information from the entire image to detect transitions in the signal, whereas the traditional algorithm relies on the maxima and minima. Traditional methods are prone to errors because the method relies on a derivative; they are also sensitive to noise and blurring. The Symbology Decoding Algorithm for Bar Code Scanners exhibited high resilience to blur and noise when tested on 1D Universal Product Codes. The algorithm can also be extended for use on 2D Universal Product Codes.

Early serial interfaces

Early barcode scanners, of all formats, almost universally used the then-common RS-232
RS-232
In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...

 serial interface. This was an electrically simple means of connection and the software to access it is also relatively simple, although needing to be written for specific computers and their serial ports.

Proprietary interfaces

There are a few other less common interfaces. These were used in large EPOS
Point of sale
Point of sale or checkout is the location where a transaction occurs...

 systems with dedicated hardware, rather than attaching to existing commodity computers. In some of these interfaces, the scanning device returned a "raw" signal proportional to the intensities seen while scanning the barcode. This was then decoded by the host device. In some cases the scanning device would convert the symbology of the barcode to one that could be recognized by the host device, such as Code 39
Code 39
__FORCETOC__Code 39 is a variable length, discrete barcode symbology....

.

Keyboard wedges

With the popularity of the PC
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

 and its standard keyboard interface, it became ever easier to connect physical hardware to a PC and so there was commercial demand similarly to reduce the complexity of the associated software. "Keyboard wedge" hardware plugged between the PC and its normal keyboard, with characters from the barcode scanner appearing exactly as if they had been typed at the keyboard. This made the addition of simple barcode reading abilities to existing programs very easy, without any need to change them, although it did require some care by the user and could be restrictive in the content of the barcodes that could be handled.

USB

Later barcode readers began to use USB
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....

 connectors rather than the keyboard port, as this became a more convenient hardware option. To retain the easy integration with existing programs, a device driver called a "software wedge" could be used, to emulate the keyboard-impersonating behaviour of the old "keyboard wedge" hardware.

In many cases a choice of USB interface types (HID, CDC) are provided. Some have Powered USB.

Wireless networking

Modern handheld barcode readers are operated in wireless network
Wireless network
Wireless network refers to any type of computer network that is not connected by cables of any kind. It is a method by which homes, telecommunications networks and enterprise installations avoid the costly process of introducing cables into a building, or as a connection between various equipment...

s according to IEEE 802.11g (WLAN) or IEEE 802.15.1 (Bluetooth
Bluetooth
Bluetooth is a proprietary open wireless technology standard for exchanging data over short distances from fixed and mobile devices, creating personal area networks with high levels of security...

). However, such configuration limits the time of operation from battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...

 or rechargeable battery
Rechargeable battery
A rechargeable battery or storage battery is a group of one or more electrochemical cells. They are known as secondary cells because their electrochemical reactions are electrically reversible. Rechargeable batteries come in many different shapes and sizes, ranging anything from a button cell to...

 and required recharging at least after a shift of operation.

Resolution

The scanner resolution is measured by the size of the dot of light emitted by the reader. If this dot of light is wider than any bar or space in the bar code, then it will overlap two elements (two spaces or two bars) and it may produce wrong output. On the other hand, if a too small dot of light is used, then it can misinterpret any spot on the bar code making the final output wrong.

The most commonly used dimension is 13 mils
Thou (unit of length)
A thou also known as a mil or point, is the verbalized abbreviation for "thousandth of an inch." It is a unit of length equal to 0.001 inch....

 (0.33 mm
Millimetre
The millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length....

), although some scanners can read codes with dimensions as small as 3 mils. Smaller bar codes must be printed at high resolution to be read accurately.

See also

  • CueCat
    CueCat
    The CueCat is a cat-shaped handheld barcode reader that was developed in early 1990s and released in 1999 by the now defunct Digital Convergence Corporation, which connected to computers using the PS/2 keyboard port and USB...

    , a cat-shaped handheld barcode reader.
  • Barcode Battler
    Barcode Battler
    The is a handheld gaming console released by Epoch in March 1991.The console at retail was supplied with a number of cards, each of which had a barcode. Upon starting the game, the player must swipe a barcode representing a player. The game uses barcodes to create a character for the player to...

    , a portable game console which scans barcodes as part of the gameplay
  • Barcode
    Barcode
    A barcode is an optical machine-readable representation of data, which shows data about the object to which it attaches. Originally barcodes represented data by varying the widths and spacings of parallel lines, and may be referred to as linear or 1 dimensional . Later they evolved into rectangles,...

    for more details about the Barcode technology
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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