Barcode Scanning Overview

Scanning Physics and Terminology
Scanning Methods
Laser Scan Engines
1D Barcode Symbologies
2D Barcode Symbologies
Decoded vs. Undecoded

Scanning Physics and Terminology   Top

Yes, it's a science. Put simply, a scanning device simply emits a bright light and reads what is reflected back to it. The black lines of a barcode reflect less light, and more light is reflected by the white spaces. The "decoder" then figures out that it is a barcode, what symbology it is (more on "symbology" later), and what information is in that barcode.

Aggressive: the relative ability of the scanner to read a barcode on the first attempt.

Depth of Field: the distance from the front of the scanner to the barcode.

Mil: The width of the narrowest bar in a barcode, measured in 1/1000ths of an inch. The width of the narrowest bar of a 15 mil barcode is 15/1000ths of an inch. This is also sometimes referred to as the "X dimension." With respect to scanners, the overall height or width of a barcode is not necessarily important, but the "mil" is vitally important.

Scanning Methods   Top

Wand:
Perhaps the least expensive way to scan a barcode, the wand is a pen-like device that must be in contact with the barcode. It also must be held at a certain angle, and be passed over the barcode at a consistent speed (neither too fast nor too slow). With these requirements in mind, wands have a high 'frustration factor' making them difficult to use at times. Wands present a variety of challenges that make them most useful when price is the most important factor.

CCD:
A CCD is a scanning "gun" that, floods the barcode with light, then reads what's reflected back to it. It's more expensive than the wand, but is also more efficient and easy to use. It can only read barcodes from a close distance (less than 6" in most cases) and can only read barcodes that are no wider than the scanner itself. However, CCD's have the reputation of being highly reliable. They're great for light-to-medium retail and out-of-doors applications where sunlight makes it difficult for the scanner to"see" what is being scanned.

Laser:
Though laser scanners are more expensive than wands and CCDs, they are the laser scanners most versatile (see "Laser Scan Engines" below) and aggressive tools for scanning barcodes. A laser beam is emitted from the scanner that either reads left-to-right and right-to-left, or vice versa. With the cost of laser scanners coming down, typically we would recommend going with a laser scanner.

Imager:
It is not possible for a wand, CCD, or laser scanner to read a matrix code (see "2D Symbologies" below). Enter the imager. These devices can not only read matrix codes, but also1D and other 2D Symbologies. And imagers can be used in the creation of ID cards that require a picture of the person. They basically work by taking a picture of the item scanned. From there they analyze the image. Though much pricier, these scanners can be used in situations requiring large amounts of data to be stored in the barcode.

Laser Scan Engines   Top

It's not possible for one scanner to be all things to every customer. Because of this, there are scanners that are designed to be used in very specific applications. Before you ask for a scanner, you must first know the symbology of the barcode and the mil of that barcode (if applicable).

Standard
If there were a scanner that attempts to be all things to everybody, this would be it. It would likely read 1D barcodes that are between 5 and 20 mils.

High Density
High density scanners are used for reading small, dense barcodes, such as those typically found on jewelry tags. This type of scanner might, for example, read down to a 2-mil barcode and up to a 7-mil barcode.

High Visibility
Remember that a scanner reads what is reflected back to it. However, if the scanner were being used in a very bright environment, the light that would normally be reflected back would be "washed out" by the ambient light, such as sunlight. So a high visibility scanner has a brighter beam of light to overcome this problem.
 

Long Range
In a warehouse environment, it is sometimes necessary to read a barcode from a long way away - such as 40 feet! Long Range scanners will typically have an "aiming beam," which is a bright dot to assist the user in locating the specific barcode that the user wishes to scan. To be able to read a barcode from 40 feet away, the barcode should be very large and printed on material (called "retroreflective") that can reflect, rather than absorb, a lot of light.

Omni-directional
All of the above scanners require the barcode to be turned in a specific direction because they only emit a single line. An Omni-directional scanner emits a pattern of several lines. Think about a visit to the grocery store. Can you imagine how slow it would be if the cashier had to make sure that every barcode was turned in a specific direction? Where Omni-directional scanners are being used, the user can have a bottle standing up, or lying on its side, or at an angle as the bottle is presented to the scanner. It doesn't matter which way the barcode is positioned.
 

2D Scanners
These are not to be confused with Imagers. 2D laser scanners "raster," which means they scan left to right, right to left, and up and down. Typically, they will only read PDF417 and 1D Symbologies. These scanners also are generally more expensive than conventional 1D scanners.

1D Barcode Symbologies   Top
1D - one dimensional
These are symbologies that only include vertical lines and spaces. There are more symbologies than are listed here, but these are some of the most common.

UPC
UPC is a 12-digit symbology that is used in retail applications.

UPC- A
UPC-A is what you normally would see, for example, on a box of cereal. This numeric-only barcode is basically broken up into 3 parts. The first character is what is referred to as the System Digit and is a way of identifying the industry to which the product might be associated. The next 5 digits identify the manufacturer. The manufacturer must acquire this number from the Uniform Code Council. The next 5 digits are the manufacturer's way of identifying the product. The last digit, known as the "check digit," is the result of a mathematical calculation using the previous 11 digits.

UPC-E
UPC-E, a compressed version of an UPC-A, would be typically seen on a can of soda or pack of gum, where there is not much available space. UPC-E will not have a system digit, and the zeros from the UPC-A will be "suppressed." Therefore, UPC-E can be expanded back into a valid UPC-A code.

Supplementals: Two or five-digit supplementals are commonly found on periodicals or publications. A supplemental is a small barcode that is to the right of the UPC-A or -E barcode.

EAN
The European Article Numbering system is a European version of UPC. Country codes are used to allow the use of one barcode both internationally and omestically. For example, 00, 02, 03, 04, 05, 06, 07, and 09 are assigned to USA and Canada, while 40 - 43 are all used for Germany.

EAN-13
EAN-13 is basically an UPC-A with a leading digit, which is usually representative of a country code. Two and five digit supplementals are supported.

EAN-8
This is a smaller version of the EAN-13. It also has a two-digit country code, followed by data and a check digit.

ISBN (International Standard Book Number):
Also called "Bookland," this symbology is used on books and other publications. Though it is part of the EAN family, there are no country codes used. The ISBN number is simply preceded by "978" or "979." The 5-digit supplemental is simply the price preceded by a "5."

Code 39
A Code 39 barcode will always begin and end with the pattern of "narrow-narrow-wide-wide-narrow" bars. Code 39 is probably the most popular symbology other than UPC. It can encode numbers, uppercase letters, and a dash. The "full ASCII" version of Code 39 will additionally encode $, ?, +, and %.

Code 128
Code 128 is a unique symbology, which includes "subsets" for encoding different characters. Subset "A" will encode uppercase alphanumeric characters, subset "B" will encode lowercase alphanumeric characters, and subset "C" will only encode numbers. A nice feature of this symbology is that it is possible to have all 3 subsets in a single barcode. By combining all 3 subsets, you could actually produce a barcode that is "Code128."

Code 93
Code 93 is an enhanced version of Code 39. Basically, Code 93 will encode every character on a keyboard, including uppercase and lowercase letters, numbers, and other symbols.

Interleaved 2 of 5
"I 2 of 5" is a numeric only symbology that must contain an even number of digits. It is actually possible to get a partial, but valid scan of an I 2 of 5 barcode because the barcode is in pairs. The odd position digits are encoded in the bars and the even position digits are encoded in the spaces. Be sure to program your scanner or decoder for the exact number of characters in your I 2 of 5 barcode.

Standard 2 of 5
The difference between Standard and Interleaved 2 of 5 is that with Standard, the data is only in the bars and not the spaces.

Codabar
Here, the barcode must begin and end with an A, B, C, D, E, N, T, or *, which cannot be used anywhere else within the barcode. Codabar, commonly used in libraries, blood banks, and by overnight delivery services, can only encode numbers and the following characters: $, :, /, ., and +.

2D Symbologies   Top
2D - two dimensional. It is sometimes not possible to put all the required data into the limited amount of available space using a 1D barcode. For example, several states have begun putting 2D barcodes on the back of driver's licenses. Encoded into this barcode is all of the data that is printed on the license. 2D barcodes are also being used for tracking printed circuit boards in computer equipment.

Stacked codes
Stacked codes are made up of bars and spaces that are stacked on top of each other.

PDF417
PDF417, which was designed by Symbol Technologies, has a maximum capacity of 1,850 text characters, 2,710 digits, or a total of 1,108 bytes. PDF417 has several levels of "error checking" which allow a scanner to decode the barcode even when it has been damaged. The more error checking that is built into the barcode, the larger it becomes.

Code 16K
Developed by Laserlight Systems, Code 16K can encode a maximum of 77 text characters or 154 digits and can contain between 2 and 16 rows. The structure of the barcode is based on Code 128.

Code 49
Code 49, developed by Intermec Corporation, was the first stacked barcode symbology. A cross between UPC and Code 39, Code 49 has the ability to pack 170 alphanumeric characters within one square inch.

Matrix codes
Matrix codes almost look as if they have no form within a square. Matrix codes are able to encode even more information in a smaller space than a stacked code.

MaxiCode
United Parcel Service originally developed MaxiCode. Easily identified by its bull's eye in the middle of the barcode, MaxiCode is capable of containing about 100 characters in a one-inch square symbol. It also has error checking capabilities, as it is still possible to get a good read even though 25% of the barcode is destroyed or missing.

DataMatrix
DataMatrix is an extremely efficient symbology developed by CiMatrix. DataMatrix is most commonly used on printed circuit boards, as it can store up to 50 characters in a square symbol that is only 2mm or 3mm in size. It can also be as large as 14". Aztec The Aztec code, developed by Welch Allyn, Inc., has a maximum capacity of 3,067 letters or 3,832 numbers, or a total of 1,914 bytes of data. Like the MaxiCode, it also has a bull's eye, but its bull's eye is square.

Decoded vs. Undecoded   Top

A scanning solution generally involves 4 components: the scanner, the barcode decoder, the host communications, and the host.

"Decoded" scanners have the decoder and host communications abilities built in to them, making it possible to connect the scanner directly to a PC, for example.

"Undecoded" scanners must be connected to a device which is capable of decoding the scanned barcode. Many times, an undecoded scanner will be connected to a "decoder" or "wedge," but they might also be connected to a Portable Data Terminal.

A "decoder" or "wedge" is basically a box that serves two functions: decode the barcode and transmit that data to the defined host. The barcode decoder inside this box is often capable manipulating the data as well as decoding the barcode. For example, a decoder can add a character before the barcode or after the barcode, or even delete data.

This leaves the other side of the equation: communications. For a scanner to provide the user with what he expects, the scanner or decoder box must be programmed to communicate with the device to which it is connected. Just because the physical connection is correct does not mean that the decoder will know how to communicate with that device.