

Barcode Reader Technology Overview

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Scanning methods are distinguished by the amount of operator manipulation required:

  • Pen or wand-type readers: requires the operator to swipe the pen over the code.
  • Semi-automatic handheld readers: The operator need not swipe, but must at least position the reader near the label
  • Fix-mount readers for automatic reading: The reading is performed laterally passing the label over the reader. No operator is required, but the position of the code target must coincide with the imaging capability of the reader and ll
  • Reader gates for automatic scanning: The position of the code must be just under the gate for short time, enabling the scanner sweep to capture the code target successfully.

Types Of Technology

The reader types can be distinguished as follows:

Pen Type Readers

Pen type readers consist of a light source and a photodiode that are placed next to each other in the tip of a pen or wand. To read a bar code, the tip of the pen moves across the bars in a steady motion. The photodiode measures the intensity of the light reflected back from the light source and 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 dots and dashes are decoded.

Laser Scanners

Laser scanners work the same way as pen type readers except that they use a laser 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 tuned to a specific frequency and the photodiode is designed to detect only this modulated light of the same frequency.

CCD Readers


Camera-Based Readers

2D imaging scanners are the fourth and newest type of bar code reader currently available. They use a small video camera to capture an image of a bar code. The reader then uses sophisticated digital image processing techniques to 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.

There are a number of open source libraries for barcode reading from images. These include the ZXing project, which reads one- and two-dimensional barcodes using Android and JavaME, the JJIL project, which includes code for reading EAN-13 barcodes from cellphone cameras using J2ME, and Zebra (Changed name to ZBAR), which reads various one-dimensional barcodes in C. Even web site integration, either by image uploads (e.g. 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





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.



PDA scanner: a PDA with a built-in barcode reader or attached barcode scanner e.g. Grabba.

Automatic reader: a back office equipment to read barcoded documents at high speed (50,000/hour) e.g. Multiscan MT31

Methods Of Connection

Early Serial Interfaces

Early barcode scanners, of all formats, almost universally used the then-common RS232 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.{10}

Proprietary Interfaces


Wand emulation is another output type that takes the raw wave and decodes it, normalizing the output so it can be easily decoded by the host device. Wand emulation can also convert symbologies that may not be recognized by the host device into another symbology (typically Code 39) that can be easily decoded.{11}

Keyboard Wedges


Later barcode readers began to use USB 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.

PS/2 Port

Most barcode readers now use a PS/2 or USB cable for output: PS/2 cables are connected to the host computer in a Y formation, the PS/2 keyboard port with its first end, to the keyboard with its second, and to the barcode reader with its third end. The barcode characters are then received by the host computer as if they came from its keyboard decoded and converted to keyboard input within the scanner housing. This makes it easy to interface the bar code reader to any application that is written to accept keyboard input

USB is supported by many newer scanners. 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 networks according to IEEE 802.11g (WLAN) or IEEE 802.15.3 (Blueooth). However, such configuration limits the time of operation from battery or rechargeable battery and required recharging at least after a shift of operation.



The most commonly used dimension is 13 mils (0.3302 mm). As it is a very high resolution, it is extremely important to have bar codes created with a high resolution graphic application.

While cell phone cameras are not suitable for many traditional barcodes, there are 2D barcodes (such as Semacode) which are optimized for cell phones. These open up a number of applications for consumers:

  • Movies: DVD/VHS movie catalogs
  • Music: CD catalogs, play MP3 when scanned
  • Book catalogs
  • Personal Property inventory (for insurance and other purposes)
  • Calling cards: 2D barcodes can store contact information for importing.
  • Brick and mortar shopping: Portable scanners can be used to record items of interest for looking up online at home.
  • Coupon management: weeding expired coupons.
  • Personal finance. Receipts can be tagged with a barcode label and the barcode 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.

Code 39

Code 39 (known as "USS Code 39", "Code 3/9", "Code 3 of 9", "USD-3", "Alpha39", "Type 39") is a barcode symbology that can encode uppercase letters (A through Z), digits (0 through 9) and a handful of special characters like the $ sign.

A Code 39 Barcode Label

The barcode itself does not contain a check digit (in contrast to&mdash;for instance&mdash;Code 128), but it can be considered self-checking by some; on the grounds that a single erroneously interpreted bar cannot generate another valid character.

Possibly the most serious drawback of Code 39 is its low data density: It requires more space to encode data in Code 39 than, for example, in Code 128. This means that very small goods cannot be labeled with a Code 39 based barcode. However, Code 39 is still widely used and can be decoded with virtually any barcode reader. One advantage of Code 39 is that since there is no need to generate a check digit, it can easily be integrated into existing printing system by adding a barcode font to the system or printer and then printing the raw data in that font.

The name Code 39 is derived from the fact that three of the nine elements that constitute a codeword are wide elements, the remaining six are narrow. Code 39 was developed by Dr. David Allais and Ray Stevens of Intermec in 1974. It was later standardised as ANSI MH 10.8 M-1983 and MIL-STD-1189. The width ratio between narrow and wide can be chosen between 1:2 and 1:3.

The details of CODE 39 can be seen in Appendix A.


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