Using Barcode to store data is a usual technique for automatic data collection(ADC). Barcode had been apply to many area such as : Office Automation, Building Automation, and Factory Automation. The conventional bar code used in supermarkets consists of a serial number coded in black and white bars.(see Fig. 1) This kind of bar codes is "1D Barcode" which stores only a identifying number ,and we need to access database if detail information is required. The most obvious limitation of "1D Barcode" is the amount of data that can be stored , though other problems can exist with the substrate that the barcode is printed on providing insufficient contrast or poor ink receptivity which can cause the quality of the barcode to be less than ideal. The most common examples in use today are: UPC/EAN/JAN, Code 128, Code 39, Code 93,and Interleaved 2 of 5. Typical data content capacity varies from 8 to 30 characters with some barcodes restricted to numerals only, and others using full alphanumeric information.
We list some common Barcodes which been use in many area:
UPC(Universal Product Code)
EAN(European Article Numbering)
Interlard 2 of 5
Code 3 of 9
ISBNcode(International Standard Book Number)
A new growth area in the world of barcode is the two-dimensional versions. 2D Barcodes have been introduced for much higher
density. It can store the desired information such that we don't need to access a database. 2D Barcodes also bring higher reliability and security because their greater capacity allows to add extra data to do error correction and data security.The advantage of 2D codes is that
they can store vast amounts of data. But the disadvantage is that a special scanner is required.
2D codes can be grouped into two major categories: stacked 2D codes and matrix 2D codes. Stacked 2D codes are stacked by several rows of 1D Barcode.However, matrix 2D code are have thrie own method to encode data.Now,we introduce some common examples of stacked 2D codes and Matrix 2D codes.
Stacked 2D codes:
1. PDF417 is a two-dimensional, stacked, public-domain barcode developed in 1990 by Symbol Technology. It is a multi-row, continuous, variable length symbology that has high data capacity of storing up to about 1,800 printable ASCII characters or 1,100 binary character per symbol.
2. Code 16K, developed by Ted Williams of LaserLight Systems in 1989, is a multiple-row variable-length symbology encoding the full ASCCII 128 character set. Williams also developed Code 128, and the structure of Code 16K is based on existing UPC and Code 128 character patterns. There are between two and 16 adjacent rows, each divided by a separator bar. Rows are
identified by the use of unique start/stop patterns.
3. Code 49 was developed in 1987 by Intermec Technologies to fill a need to pack a lot of information into a very small symbol. It's a multiple-row, continuous, variable symbology encoding the full ASCII 128 character set. Each row is composed of 18 bars and
17 spaces. There are between two and eight adjacent rows, each divided by a separator bar. Each row contains a row number, and
the last row contains information indicating how many rows there are in the symbol.
Matrix 2D codes:
1. DataMatrix :The public domain code DataMatrix was developed by International Data Matrix (now CiMatrix). DataMatrix is a variable size 2D matrix symbology containing dark and light square data modules. It has a finder pattern of two solid lines and two alternating dark and light lines on the perimeter of the symbol for symbol identification, orientation and cell location. DataMatrix is designed with a fixed level of error correction capability.DataMatrix is used for small item marking applications using a wide variety of printing and marking technologies. The symbol can contain from 1 to 2000 characters of information.
2. QR Code :Denso of Japan developed QR Code (Quick Response Code) as a two-dimensional matrix symbology having position detection patterns on its three corners. QR Code features mass data capacity, high data density and error correction ability, ultra high speed, omni-directional reading and Japanese Kana-Kanji representation. QR Code is in the public domain and it is read by using CCD array cameras and image-processing technology because of the layout of the finder pattern.
3. Maxicode : A fixed-sized 2D matrix symbology, MaxiCode (originally called UPS Code), was developed by United Parcel Service. This public domain code is made up of offset rows of hexagonal elements arranged around a central, bulls-eye finder pattern. Hexagonal elements allow dense packing, and provide fixed center-to-center spacing of all elements. The central finder pattern and fixed symbol size allow for easy scanning on high-speed conveyors.
Our laboratory had develop a system of our own 2D Code,and using it on many applications.
C.T.Yeh and L.H.Chen, " A System for a New Two Dimensional Code : Secure 2D Code ", Machine Vision and Applications (accepted).