How do barcodes and barcode scanners work?

How barcodes represent the numbers 0–9

A barcode is a really simple idea: give every item that you want to classify its own, unique number and then simply print the number on the item so an electronic scanning device can read it. We could simply print the number itself, but the trouble with decimal numbers is that they're easy to confuse (a misprinted eight could look like a three to a computer, while six is identical to nine if you turn it upside down—which could cause all sorts of chaos at the checkout if you scanned your cornflakes the wrong way up). What we really need is a completely reliable way of printing numbers so that they can be read very accurately at high speeds. That's the problem that barcodes solve.

Photo: Each digit in a barcode is represented by seven equal-sized vertical blocks. These are colored in either black or white to represent the decimal numbers 0–9. Every number ultimately consists of four fat or thin black and white stripes and its pattern is designed so that, even if you turn it upside down, it can't be confused with any other number.

If you look at a barcode, you probably can't make head or tail of it: you don't know where one number ends and another one begins. But it's simple really. Each digit in the product number is given the same amount of horizontal space: exactly 7 units. Then, to represent any of the numbers from zero through nine, we simply color those seven units with a different pattern of black and white stripes. Thus, the number one is represented by coloring in two white stripes, two black stripes, two white stripes, and one black stripe, while the number two is represented by two white stripes, one black stripe, two white stripes, and two final black stripes.

You've probably noticed that barcodes can be quite long and that's because they have to represent three different types of information. The first part of a barcode tells you the country where it was issued. The next part reveals the manufacturer of the product. The final part of the barcode identifies the product itself. Different types of the same basic product (for example, four-packs of Coca-Cola bottles and six-packs of Coca-Cola cans) have totally different barcode numbers.

Most products carry a simple barcode known as the UPC (universal product code)—a line of vertical stripes with a set of numbers printed underneath it (so someone can manually key in the product number if the barcode is misprinted or damaged in the store and won't scan through the barcode reader). There is another kind of barcode that is becoming increasingly common and its stores much more information. It's called a 2D (two-dimensional) barcode) and you sometimes see it on things like self-printed postage stamps.

Photo: Two sets of very thin "guard bars" (which I've indicated in red) show where a barcode begins and ends, while a third set in the middle separates the product code (yellow) into two chunks of data (0028 and 1003 in this example). The guard bars make it easier for the scanner to detect a barcode, figure out which way up it is, and help to identify it when it's blurred (more about this down below).

How does a barcode scanner work?

It would be no good having barcodes if we didn't have the technology to read them. Barcode scanners have to be able to read the black-and-white zebra lines on products extremely quickly and feed that information to a computer or checkout terminal, which can identify them immediately using a product database. Here's how they do it.

For the sake of this simple example, let's assume that barcodes are simple on-off, binary patterns with each black line corresponding to a one and each white line a zero. (We've already seen that real barcodes are more sophisticated than this, but let's keep things simple.)

1. Scanning head shines LED or laser light onto barcode.
2. Light reflects back off barcode into a light-detecting electronic component called a photoelectric cell. White areas of the barcode reflect most light; black areas reflect least.
3. As the scanner moves past the barcode, the cell generates a pattern of on-off pulses that correspond to the black and white stripes. So for the code shown here ("black black black white black white black black"), the cell would be "off off off on off on off off."
4. An electronic circuit attached to the scanner converts these on-off pulses into digits.
5. The digital data from the scanner is sent to a computer program, which figures out the final barcode.

In some scanners, there's a single photoelectric cell and, as you move the scanner head past the product (or the product past the scanner head), the cell detects each part of the black-white barcode in turn. In more sophisticated scanners, there's a whole line of photoelectric cells and the entire code is detected in one go.

How do scanners cope with moving objects?

One major complication here is that the barcode (or the scanner) is often moving during the scanning process (think how you swipe items at a self-serve grocery checkout) or it might be so far from the scanner that the code is out of focus. That means the pattern the scanner produces is not a crisp set of easy-to-identify black and white stripes, but a blurred smudge made of more ambiguous grey shades. Various different computer algorithms can be used to turn these blurred patterns into accurate barcodes, including edge-detection, which looks for sudden changes in brightness where a zero gives way to a one, or vice-versa. If you want to know exactly how these algorithms work, check out the technical references at the end of this article.

Photo: Left: Barcodes as we see and think of them are clear and crisp zebra patterns. Middle: Barcodes as scanners capture them may be smudged beyond recognition. Right: Using edge-detection and other algorithms, it's possible to turn blurred images back into something like a usable barcode.

Types of barcode scanner

Photo: A typical wand-type barcode scanner (also called a barcode reader). Readers like this are usually wired to computers or checkouts and contain little or no computing power. Photo by Naoto Anazawa courtesy of US Air Force and DVIDS.

Different types of barcode scanners are available for all kinds of applications. In small, convenience stores, you'll typically find a basic wand scanner. The simplest ones look like electronic pens or giant, oversized razors. They shine red LED light onto the black and white barcode pattern and then read the pattern of reflected light with a light-sensitive CCD or a string of photoelectric cells. If you have a pen scanner, you have to run it across the barcode so it can reach each block of black or white in turn; with a wand scanner, the CCD or photocells read the entire code at once.

Photo: Scanning a barcode with Amazon's iPhone/iPod app. You find a product you like, scan the code, and the online store pops up with the product details automatically.

In a busy superstore, you're more likely to see a very sophisticated laser scanner. It'll be built into the base of the checkout lane, under a piece of glass, and you may be able to see the laser beam being bounced around at high-speed by a spinning wheel so it reads products (literally) in a flash. Another technology uses a small video camera to take an instant digital photograph of the barcode. A computer then analyzes the photograph, picking out only the barcode part of it and converting the pattern of black and white bars into a number. (Barcode-scanning apps that run on cellphones work this way, using the phone's built-in camera to photograph the code.) Scanners like this can accurately read dozens of products waved past them each minute and are far more accurate than old-style checkouts (where you have to key in the price of every item by hand). The best barcode scanners are so accurate that they make only one mistake in something like 70 million pieces of scanned information! (Compare that to typing on a keypad, where you're typically likely to make one error in every 100 characters you type.)

Photo: A handheld computer with built-in barcode scanner. Unlike a simple wand-type scanner, this one can store and process data from the objects it scans, which can be uploaded to a computer later on using WiFi, Bluetooth, or the built-in cellphone connection. Photo by Taylor L. Jackson courtesy of US Navy and DVIDS.

Barcode scanning technology has been around since the early 1970s but only really caught on in the 1980s and 1990s after stores started to invest in sophisticated, computerized electronic point-of-sale (EPOS) checkout terminals. Back then, store checkouts cost many thousands of dollars. Today, scanners are much more affordable. You can buy a simple, USB barcode scanner and software and hook it up to an ordinary laptop or computer for just a few dollars. Thanks to barcodes, even tiny convenience stores can run as smoothly as Wal-Mart these days!

Who invented barcodes?

How did we arrive at a point where virtually everything we buy is marked with a barcode? Here are some of the key moments in barcode history:

• 1948:

  Bernard Silver

  (1924–1963) and

  N. Joseph Woodland

  (1921–) get the idea for developing grocery checkouts that can automatically scan products. Woodland tries various different marking systems, including lines and circles, marks inspired by movie soundtracks, and dots and dashes based on Morse code. In October 1949, the two inventors refine their system to use bullseye patterns and apply for a patent (US Patent #2,612,944), which is granted on October 7, 1952. Their early barcode-scanning equipment uses a conventional lamp to illuminate product labels and a photomultiplier (a crude type of photoelectric cell) to read the light reflected off them. In 1951, Joe Woodland joins IBM to work on barcode technology, though the company declines to purchase his patent, which is acquired by Philco (and later RCA).

  Artwork: The original barcodes didn't use "zebra" stripes, like they do today, but "bullseye" patterns like these. Artwork from US Patent #2,612,944: Classifying apparatus and method by Woodland and Silver, courtesy of US Patent and Trademark Office.

• 1960s: RCA develops a number of commercial applications until the patent expires in 1969. Work on bullseye barcodes continues, but they prove unreliable and gradually fall by the wayside.
• 1970: By now, grocery stores are beginning to explore the idea of using their own product coding and marking systems, but different stores are considering different systems, and this threatens to cause problems for large food manufacturers who sell branded goods to multiple retailers. Under the guidance of

  Alan Haberman

  (1929–2011), executive vice president of First National Stores in Boston, the stores come together to form the Uniform Code Council (UCC), later known as GS1 US, the organization that now manages barcode standards worldwide.
• 1971: Meanwhile, at IBM, engineer George J. Laurer (1925–) builds on Woodland's ideas to develop the Universal Product Code (UPC)—the modern black-and-white striped barcode. (Read more about Laurer's work and IBM's contributions to barcode technology.)
• 1973: After examining a variety of different marking systems, Haberman's grocery stores committee settles on IBM's rectangular UPC as the standard grocery barcode. Although he didn't invent the barcode, Haberman is widely credited with its universal adoption.
• 1974: On June 26, the world's first grocery-store barcode scanner goes into use at Marsh's Supermarket, Troy, Ohio in the United States. The first scanned purchase, made by Clyde Dawson, is for a 10-pack of Wrigley's chewing gum.
• 1979: In the UK, a barcode scanner is used for the first time at Key Markets in Spalding, Lincolnshire.
• 2011: Joe Woodland and the late Bernard Silver are inducted into the National Inventors Hall of Fame in recognition of their brilliant invention.

The original barcode scanner

I've dipped into the archives of the US Patent and Trademark Office and pulled out the records of the original barcode pattern scanner, invented by N. Joseph Woodland and Bernard Silver. I've colored and numbered it to quickly illustrate how it worked. In the top picture, you can see the entire apparatus, including the barcode scanner, which is shown in the center in blue; in the lower picture, you can see a more detailed view of the scanner itself:

Artwork courtesy of US Patent and Trademark Office. You can find a full description and more detailed drawings in US Patent #2,612,944: Classifying apparatus and method by Norman J Woodland and Bernard Silver.

1. Like modern packages in grocery stores, Woodland and Silver envisaged items would have barcodes printed on one face.
2. You place the item to be scanned with its barcode face down on a conveyor made of some transparent material.
3. A variety of lights shine up on the barcode.
4. The scanner picks up light reflected off the barcode.
5. The scanner sends a signal to a sorting mechanism that can push the item in different directions.
6. The item is pushed onto different conveyors according to its particular barcode.
7. Now looking in closeup at the scanner: It has a lens on top that spreads the light reflected off the barcode.
8. The light from the lens spreads out onto a larger glass surface.
9. An electric motor and axle (red) move a scanning head (green).
10. Guided by the grooves in the axle, the scanning head moves from side to side.
11. A photoelectric cell (orange) inside the scanning head picks up the pattern of light and dark areas from the barcode, sending corresponding signals to a detector circuit.

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Running a warehouse, operating a functioning factory, and even purchasing your weekly shopping at the supermarket has never been easier now, thanks to the incredible practicalities of a barcode.

Everything from cereal packets to library books has a barcode. They may seem simple and often go unnoticed in our daily lives, but these black and white zebra stripes are essential to the smooth running of many operations. So, while we see the humble barcode every day, do you ever stop to think how they actually work?

The Invention of the Barcode

There’s no doubt that the invention of barcodes has made life much easier. Before we had barcode technology, our processes and structures were somewhat simpler. However, while they were manual, they caused more errors, and data wasn’t as accurate as it is today.

Norman Joseph Woodland and Bernard Silver initially invented the barcode in 1948 to make reading product information much easier during checkout processes. The initial prototype used ultraviolet ink; however, this didn’t operate as the pair had hoped. While the first attempt didn’t entirely work out, it didn’t stop the inventors from trying again. They adapted a version made from the structure of Morse code, where they utilised dashes and dots.

To read the barcode, an incandescent light bulb would shine light over the barcode pattern, through the paper and then onto a super-sensitive light detector. The black lines on the barcode absorb the light, and the white parts of the barcode would shine through and be detected.

How Do Barcodes Work in the Present Day?

The modern-day one-dimensional barcode is read using a scanner. This scanner sends out a laser that detects the pattern. When the laser of a particular frequency sweeps across the barcode, some light is absorbed while the rest reflects.

Dots and Lines

While a computer can trump the human brain in many ways, they can still only essentially read binary or base 10; 0’s and 1’s. This is one of the main reasons a barcode looks the way it does. Think of the black and white as 0’s and 1’s, or on and offs.
Considering what we know about the light reflection, the black parts don’t reflect very well; therefore, they are recorded as a 1. However, the light scanner recognises the white sections, so they are seen as 0’s.

What Do the Numbers on a Barcode Mean?

Most barcodes display a twelve-digit number, usually printed underneath as a backup for possible complications. Here are what the numbers represent:
First Number: Product Type. The product type is typically denoted by 0,1,6,7 or 8.
Following 5 Numbers: The Manufacturer Code. The five numbers are a unique code that identifies the manufacturer or distributor of the product.
Following 5 Numbers on the Right: Product Code. This part of the code is unique to the individual product.
Final Number: Check Digit (a Self-Policing System). The final digit of a barcode number is a computer check digit which makes sure the barcode is correctly composed.

The barcode scanning system detects the amount of light, which is then translated into a set of digits or data. Information can be retrieved from a computer database using this data.

What Does a Barcode Do?

Each element of a 1D barcode (1 digit in barcode language) is divided into seven vertical modules consisting of individual bars and spaces. The computer interprets these groups as 1 digit only. For example, the number 1 is 0011001 (or a series of spaces and bars). So, while you may not necessarily notice it, there are, in fact, 95 evenly spaced columns on each barcode, all with separate detailed data.

However, there are a variety of diverse types of barcodes. The most common type is UPC or Universal Product Number restricted to around 20 alpha-numerical characters. Any more than that would need a QR (2D Barcode) code.
Essentially a barcode is a way to encode information in a visual pattern that a scanner can read. It is a rapid way of inputting numerical data, and there is no doubt that they make processes much easier and quicker.

Barcoding Systems for Companies

For companies, barcodes play a crucial part in shipping and tracking items. They can also be used to manage stock as a barcode can keep track of the number of products in storage. The barcode is utilised in many industries, from health care and classifying unique patient IDs to clothing and grocery retailers for product identification. It is clear that shopping experiences would be much more difficult without the barcode.

If you are ready for a total integrated barcoding system for your business, GSM Barcoding can help. Our asset tracking systems and barcode label printing are ideal for assisting companies manage their stock and product identification. Ready and waiting with the latest and innovative technology, we can take your business to more streamlined and smooth structures. Simply get in touch today for more information.