Machine-readable barcode tags are represented by patterns of vertical parallel lines with variable spaces between them and line widths (one dimensional), or by using geometric matrix patterns (two-dimensional). Information about the product is encoded within the products bar ode through symbology. Barcode symbology encodes information within barcodes by using single characters, start and stop markers embedded in geometric patterns, relative sizes of empty space known as the 'quite zone' surrounding the barcode, and checksum calculations.
One-dimensional barcodes are used for products requiring automatic identification, data collection, and monitoring. They consist of five symbology categories which are: continuous, binary, module, interleaving, and discrete. Examples of types of one-dimensional barcodes include: Code 39, Databar and Data matrix (DM), Interleaved 2-of-5, EAN-8. EAN-13 (food retail), and EAN/UPC128-code (food processing).
Two-dimensional barcodes have a higher capacity to store information compared to one-dimensional barcodes. They use specific geometric patterns inside of a matrix to store data, and store data by blanking our modules inside of a geometric pattern. There are two categories of two-dimensional bar codes: matrix codes and 2D-stacked codes. Three common types of matrix codes are Quick Response (QR) codes, Data Matrix (DM) codes, and 2D-stacked codes.
QR codes use dark and light modules in a field matrix of fields. Each field determines the pixel size of a single module, and each QR code consists of an encoding region and a function patters. Function patterns are used to ensure QR codes are readable, and encoding patterns provide information about the QR code format, version, correction of data errors, and code words.
Components of a Quick Response (QR) code.
DM code uses dark and light modules within square or rectangular geometric patterns consisting of a finder pattern and data pattern. The finder pattern determines the basic structure of the code by defining its shape, dimension, rows, columns, and code errors.The data pattern uses dark and light modules for numeric data encoding within the DM code.
Components of a Data Matrix (DM) code.
2D-stacked codes stack 1D barcodes into rectangular blocks with multirow matrix patterns. They contain distinct patterns for storing data modules, start indicators, stop indicators, right/left indicators, and have redundant information stored within their data modules to detect and correct errors within their code. Two common types of 2D-stacked codes are the Reduced Space Symbology 14 (RSS14) and the Portable Data File 417 (PDF417).
Structure of a Portable Data File 417 (PDF417) code.
1D and 2D barcodes differ in their advantages and disadvantages. 2D barcodes can story significantly more data in the form of thousands of characters and numbers, and 1D barcodes are limited to storing 28 bits of information. 1D barcodes are fixed in while 2D barcodes can vary in size and scale. 2D barcodes are more readable when damaged compared to 1D barcodes. For example, 2D matrix codes can still be readable with approximately up to 30% damage, and 2D-stacked codes are maintain readability with up to 50% damage. 2D barcodes can be read from any rotation angle relative to the item they are attached two; except for 2D-stacked codes which have a readable maximum rotation angle of approximately three rows relative to the 2D-stack coded item. 2D barcodes also have the capacity to store a variety of information that 1D barcodes cannot store such as images, sounds, words, and fingerprints in several different programming languages.
Organizations setting barcode standards for product traceability include Global Standardization 1 (GS1), the International Organization for Standardization (ISO), and the Uniform Code Council (UCC). The organizations responsible for setting barcodes standards are focused on creating barcode standards for open loop traceability systems involving stake holders outside of a companies internal (closed loop) traceability procedures. All open loop traceability operations of an organization must comply with the international standards set out by the GS1, UCC, and ISO organizations.
