Barcode

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A barcode (also bar code) is a machine-readable representation of information in a visual format on a surface. Originally barcodes stored data in the widths and spacings of printed parallel lines, but today they also come in patterns of dots, concentric circles, and hidden in images. Barcodes can be read by optical scanners called barcode readers or scanned from an image by special software. Barcodes are widely used to implement Auto ID Data Capture (AIDC) systems that improve the speed and accuracy of computer data entry.

While traditionally, barcodes encoding schemes represented just numbers, newer symbologies add new characters such as from the upper case alphabet to the complete ASCII character set and beyond. The drive to encode ever more information in combination with the space requirements of simple barcodes led to the development of matrix codes (a type of 2D barcode), which do not consist of bars but rather a grid of square cells. Stacked barcodes are a compromise between true 2D barcodes and linear codes, and are formed by taking a traditional linear symbology and placing it in an envelope that allows multiple rows.

Usage

Since their invention in the 20th century, barcodes -- especially the UPC code -- have slowly become an essential part of modern civilization. Their use is widespread and the technology behind barcodes is constantly improving. Some modern applications of barcodes include:

Practically every item purchased from a grocery store, department store and mass merchandiser has a barcode on it. This greatly helps in keeping track of the large number of items in a store and also reduces instances of shoplifting. Since the adoption of barcodes, both consumers and retailers have profited from the savings generated.
Rental car companies keep track of their cars by means of barcodes on the car bumper.
Airlines track passenger luggage with barcodes, reducing the chance of loss.
Recently, researchers have placed tiny barcodes on individual bees to track the insects' mating habits.
NASA relies on barcodes to monitor the thousands of heat tiles that need to be replaced after every space shuttle trip.
The movement of nuclear waste can be tracked easily with a bar-code inventory system.
More recently, barcodes have even started appearing on humans. Fashion designers stamp barcodes on their models to help coordinate fashion shows. The codes store information about what outfits each model should be wearing and when they are due on the runway.
In the late 1990's in Tokyo, there was a fad for temporary barcode shaped tattoos among high school girls.

Technology of barcodes

A linear barcode is a binary code (1s and 0s). The lines and spaces are of varying thicknesses and printed in different combinations. To be scanned, there must be accurate printing and adequate contrast between the bars and spaces. Scanners employ various technologies to "read" codes. The two most common are lasers and cameras. Scanners may be fixed position, like most supermarket checkout scanners, or hand-held devices, often used for the taking of inventories. There should be (but typically is not,) a distinction drawn between the code, which is a structure for the conveyance of data, and the symbol, the machine-readable representation of the code. The code is text, which can be translated into a multiplicity of languages - English, French, Japanese, symbol.

Notwithstanding its inauspicious beginning, the barcode has become a remarkable success, a workhorse in many and varied applications. One of the first successful barcodes, Code 39 developed by Dr. David Allais, is widely used in logistical and defense applications. Code 39 is still in use today, although it is less sophisticated than some of the newer barcodes. Code 128 and Interleaved 2 of 5 are other codes that attained some success in niche markets.

The Universal Product Code

The best-known and most widespread use of barcodes has been on consumer products. The Universal Product Code, or UPC, is unique because it was developed by the user community. Most technological innovations are first invented and then a need is found for the invention. The UPC is a response to a business need first identified by the US grocery industry in the early 1970s.

Believing that automating the grocery checkout process could reduce labor costs, improve inventory control, speed up the process, and improve customer service, six industry associations, representing both product manufacturers and supermarkets, created an industry wide committee of industry leaders. Their two-year effort resulted in the announcement of the Universal Product Code and the UPC barcode symbol on April 1, 1973. The UPC made its first commercial appearance on a package of Wrigley's gum sold in Marsh's Supermarket in Troy, Ohio in June 1974.

Economic studies conducted for the grocery industry committee projected over $40 million in savings to the industry from scanning by the mid-1970s. Those numbers were not achieved in that time frame and there were those who predicted the demise of barcode scanning. The usefulness of the barcode required the adoption of expensive scanners by a critical mass of retailers while manufacturers simultaneously adopted barcode labels. Neither wanted to move first and results looked unpromising for the first couple of years, with Business Week eulogizing The Supermarket Scanner That Failed.

Symbologies

The mapping between messages and barcodes is called a symbology. The specification of a symbology includes the encoding of the single digits/characters of the message as well as the start and stop markers into bars and space, the size of the quiet zone required to be before and after the barcode as well as the computation of a checksum.

Linear symbologies can be classified mainly by two properties:

Continuous vs. discrete: Characters in continuous symbologies abut, with one character ending with a space and the next beginning with a bar, or vice versa. Characters in discrete symbologies begin and end with bars; the intercharacter space is ignored, as long as it is not wide enough to look like the code ends.
Two-width vs. many-width: Bars and spaces in two-width symbologies are wide or narrow; how wide a wide bar is exactly has no significance as long as the symbology requirements for wide bars are adhered to (usually two to three times more wide than a narrow bar). Bars and spaces in many-width symbologies are all multiples of a basic width called the module; most such codes use four widths of 1, 2, 3 and 4 modules.

Stacked symbologies consist of a given linear symbology repeated vertically in multiple.

There are a large variety of 2-D symbologies. The most common are matrix codes, which feature square or dot-shaped modules arranged on a grid pattern. 2-D symbologies also come in a variety of other visual formats. Aside from circular patterns, there are several 2-D symbologies which employ steganography by hiding an array of different-sized or -shaped modules within a user-specified image (for example, DataGlyph).

Scanner/symbology interaction

Linear symbologies are optimized to be read by a laser scanner, which sweeps a beam of light across the barcode in a straight line, reading a slice of the barcode light-dark patterns.

Stacked symbologies are also optimized for laser scanning, with the laser making multiple passes across the barcode.

2-D symbologies cannot be read by a laser as there is typically no sweep pattern that can encompass the entire symbol. They must be scanned by a camera capture device.

Scanners (barcode readers)

The earliest, and still the cheapest, barcode scanners are built from a fixed light and a single photosensor that is manually "scrubbed" across the barcode.

A later design, the "laser scanner," uses a polygonal mirror or galvanometer-mounted mirror to scan a laser across the barcode -- initially only in a straight line, but eventually in complicated patterns so the reader could read barcodes at any angle.

In the 1990's some barcode reader manufacturers began working with digital cameras to capture barcodes, both linear and 2D. That technology has since been perfected and now often surpasses laser scanners in performance and reliability.

More recently, off-the-shelf digital cameras now have enough resolution to capture both 1D and 2D barcodes. Increasingly companies are looking to incorporate barcode scanning software into cameraphones. However, the camera phone optics are not well suited for standard codes that were designed for industrial dedicated scanners. As a result, new codes are being designed for mobile use such as color code and mCode.

Types of barcodes

Linear barcodes

Symbology	Cont/Disc	Two/Many	Uses
Plessey	Continuous	Two	Catalogs, store shelves, inventory
UPC	Continuous	Many	North America retail
Codabar	Discrete	Two	Old format used in libraries, blood banks, airbills
Interleaved 2 of 5	Continuous	Two	Wholesale, Libraries (NO)
Code 39	Discrete	Two	Various
Code 93	Continuous	Many	Various
Code 128	Continuous	Many	Various
Code 128A	Continuous	Many	Various
Code 128B	Continuous	Many	Various
Code 128C	Continuous	Many	Various
Code 11	Discrete	Two	Telephones
EAN 2	Continuous	Many	Addon code (Magazines)
EAN 5	Continuous	Many	Addon code (Books)
EAN 8, EAN 13	Continuous	Many	Worldwide retail
GS1-128 (formerly known as UCC/EAN-128), EAN 128, UCC 128	Continuous	Many	Various
DUN 14	Continuous	Many	Various
ITF-14	Continuous	Many	Shipping Container Symbol
Pharmacode	Neither	Two	Pharmaceutical Packaging
POSTNET	Continuous	Tall/short	United States Postal Service
PLANET	Continuous	Tall/short	United States Postal Service
OneCode	Continuous	Tall/short	United States Postal Service, replaces POSTNET and PLANET symbols
PostBar	Discrete	Many	Post office
CPC Binary	Discrete	Two	Post office
RM4SCC	Continuous	Tall/short	Royal Mail
Telepen	Continuous	Two	Libraries, etc (UK)

Stacked barcodes

Symbology	Notes
Codablock	Stacked 1D barcodes.
Code 16K	Based on 1D Code 128.
Code 49	Stacked 1D barcodes from Intermec Corp.
PDF417	The most common 2D barcode. Public domain.
Micro PDF417

2D barcodes

A matrix code, also known as a 2D barcode, is a two-dimensional way of representing information. It is similar to a linear (1-dimensional) barcode, but has more data representation capability.

Symbology	Notes
3-DI	Developed by Lynn Ltd.
ArrayTag	From ArrayTech Systems.
Aztec Code	Designed by Andrew Longacre at Welch Allyn (now Hand Held Products). Public domain.
Small Aztec Code	Space conscious version of Aztec code.
Bullseye	This was the barcode tested in a Kroger store in Cincinnati. It used concentric bars.
Codablock	Stacked 1D barcodes.
Code 1	Public domain.
Code 16K	Based on 1D Code 128.
Code 49	Stacked 1D barcodes from Intermec Corp.
Color code	Mainly used for cell phones in Korea.
CP Code	From CP Tron, Inc.
DataGlyphs	From Xerox PARC.
Datamatrix	From RVSI Acuity CiMatrix. Now Public Domain.
Datastrip Code	From Datastrip, Inc.
Dot Code A	Designed for the unique identification of items.
HueCode	From Robot Design Associates. Uses greyscale or colour.
INTACTA.CODE	From INTACTA Technologies, Inc.
MaxiCode	Used by United Parcel Service. Now Public Domain
mCode	Developed by Nextcode Corporation specifically for camera phone scanning applications. Designed to enable advanced cell mobile applications with standard camera phones.
MiniCode	From Omniplanar, Inc.
PDF417	Originated by Symbol Technologies Public Domain. The most common 2D barcode.
Micro PDF417	Facilitates codes too small to be used in PDF417.
PaperDisk	High density code -- used both for data heavy applications (10K-1MB) and camera phones (50+ bits). Developed and patented by Cobblestone Software
QR Code	De-facto standard for Japanese cell phones. Developed, patented and owned by TOYOTA subsidiary Denso Wave initially for car parts management. Can encode Japanese Kanji and Kana characters, music, images, URLs, emails.
Semacode	Based on Data Matrix code but to encode URLs for cellular phones with cameras
SmartCode	From InfoImaging Technologies.
Snowflake Code	From Marconi Data Systems, Inc.
ShotCode	Circular barcodes for camera phones by OP3. Orginally from High Energy Magic Ltd in name Spotcode. Before that probably know as TRIPCode.
SuperCode	Public domain.
UltraCode	Black-and-white & colour versions. Public domain. Invented by Jeffrey Kaufman and Clive Hohberger.
VeriCode, VSCode	From Veritec, Inc.
WaterCode	High-density 2D Barcode(440bytes/cm2) From MarkAny Inc.

External links

U.S. patent 2,612,994 - "Classifying apparatus and method"
Website of George J. Laurer - inventor of the Universal Product Code
Barcodes Sweep the World
History of the Barcode by Stephen A. Brown
How Stuff Works - UPC bar code