Barcode Scanning Technology

Barcode scanning has become a cost-effective data capture technology for enhancing processes in virtually every industry and market. Low-cost scanning solutions improve performance and reliability in a wide range of enterprise activities and deliver benefits such as increased productivity, improved task efficiency, and reduced operational costs.

A Broad Range of Barcode Types Exist to Meet the Needs of Many Industries

A barcode is an optical machine-readable representation of data. The mapping between barcodes and the data that the barcode represents is called a symbology. The three primary categories of symbologies are linear (1D), stacked and matrix (2D). The most common barcodes represent data in the widths and the spacings of parallel lines, and are referred to as linear or 1D (1 dimensional) barcodes or symbologies.

Linear Barcodes (1D)

Linear barcodes are one dimensional, meaning that the unique information is in the horizontal plane and the same information is repeated vertically. The heights of the bars can be truncated without any lose of information. This allows a symbol with printing defects, such as spots or voids, to still be read. The higher the bar heights, the more probability that at least one path along the bar code will be readable.

There are a number of 1D symbologies: UPC (numeric codes found on retail merchandise), Code 39 (numeric, uppercase letters and 7 special characters) and Code 128 (all 128 ASCII characters) are three of the more popular.

Stacked Barcodes (1D+)

Stacked barcodes are a set of linear bar codes stacked on top of each other. An example of a stacked symbology is the PDF417 format used on airline boarding passes.

2D Barcodes

2D barcodes come in patterns of squares, dots, hexagons and other geometric patterns within images termed matrix codes or symbologies. Although 2D systems use symbols other than bars, they are also generally referred to as barcodes as well. Examples of 2D codes include semacodes which are optimized for use by cell phones and the similar QR codes originating out of Japan.

Not all Barcode Readers Can Read All Barcode Types

Barcode scanners are available with basically four types of readers:
(1) Laser,
(2) linear imagers/CCD,
(3) area imagers and
(4) two-dimensional CCD.

The reader type, and software included, will determine what type of barcode symbologies can be read.

Laser Scanners

A laser scanner sweeps a beam of light across the barcode in a straight line, reading a slice of the barcode light-dark patterns. Laser scanners can project a beam of light a long distance without diverging, or spreading out, as light from other sources do, enabling them to decode high density bar codes over wide ranges. This proves advantageous in applications that require scanning range flexibility, such as forklift operations where packages are often located on high shelves or hard-to-reach areas.

Stacked linear 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. Laser scanning is the preferred technology in high-throughput areas that require motion insensitivity, such as supermarkets, where users can rapidly swipe item after item over a fixed scanner, and the required symbology is limited to 1D linear codes.

CCD Barcode Readers

Linear Imagers, also known as CCD barcode readers, use an array of LED’s and receptors to decode linear barcodes. Linear imager barcode scanners are better for reading damaged or poorly printed barcodes as well as barcodes under plastic film or covering and are ideal for a variety of applications including retail, shipping, receiving, and inventory. CCD readers can scan 1D and 1D stacked linear barcodes such as PDF417. Linear imagers use sensors to capture only a single row of pixels within the image. This allows linear imagers to decode a 1D bar code, but not entire images or 2D bar codes as an area imager can.

Digital Area Imagers

Digital area imagers use LED light that illuminates the target bar code. A lens projects the image of the bar code onto a 2D array, and the light is converted to an electrical signal to construct the digital image. Decoder software in the imager locates the bar code within the image, and processes its data using advanced decoding algorithms. Area imagers use sensors with pixels arranged in a 2-dimensional grid (multiple rows) and can read 1D and 2D symbologies.

2D Imaging Scanners

Cell phones employ two-dimensional imaging scanners. They use a small video camera to capture an image of a bar code. Sophisticated digital image processing techniques decode the bar code. Video cameras use 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.

Smartphones and Barcode Scanning

Most smart phone barcode readers can read 2D codes but not all of them can read and decode 1D codes. The factors for consideration here are whether the smartphone camera supports autofocus and whether it has a macro lens. The Android smart phone and some versions of Blackberry’s (the Tour, Storm and the 9700 but this may not be an exhaustive list) meet this criteria. As of the writing of this article, the iPhone does not have a camera lens with auto-focus but there is an app that is optimized to read the numeric UPC and EAN codes of retail products.

 A 1D barcode can only encode a number or string of characters which can be entered into a database, while a 2D barcode can actually hold the entire database. For example, you can embed an Excel spreadsheet into a 2D barcode, to use as a portable database. Most 2D symbologies can hold at least 2,000 characters per bar code. The typical 1D bar code contains about 10-20 characters.