eXtra: The Essentials of Product Identification Using Machine Vision
December 8, 2011
A Brief History of the BarcodeA barcode is a symbol that conveys information about the product to which it is attached. It is generally a pattern of black and white lines or dots that cannot be read by humans, but can be read by machines called barcode readers. Traditionally, these devices were basic laser scanners, but they have evolved to two-dimensional image scanners, also known as image-based ID readers.
The first barcode was developed by Bernard Silver and Norman Joseph Woodland. Silver was a graduate student at Drexel Institute of Technology in Philadelphia and overheard the president of a chain of grocery stores asking a dean at the school to research a way to capture product information automatically at checkout. Captivated by the problem, Silver and Woodland pursued the idea starting in 1948, using the concepts of Morse code and movie sound systems. Woodland was later hired by IBM, and he worked toward getting a patent for barcodes. IBM was able to patent the technology in 1952, and then sold it to Philco, who later sold the patent to RCA.
Barcodes were first used to label railroad cars in the early 1960s, but they were not a commercial success until they were used to automate supermarket checkout systems, with the now well-known Universal Product Code (UPC) barcode. The very first scanning of the UPC barcode was on a pack of Wrigley Company chewing gum in 1974.
Although supermarket scanning was not as successful as initially predicted, the detailed sales information acquired by the new systems allowed greater responsiveness to customer needs. Studies showed that about five weeks after installing barcode scanners, sales in grocery stores typically started climbing and eventually leveled off at a 10-12% increase in sales that never dropped off. There also was a 1–2% decrease in operating cost for the stores that enabled them to lower prices to increase market share.
In 1981 the United States Department of Defense adopted the use of a specific type of barcode symbology, Code 39, for marking all products sold to the United States military. This system, Logistics Applications of Automated Marking and Reading Symbols (LOGMARS), is still used by the Department of Defense and is widely viewed as the catalyst for widespread adoption of barcoding in industrial uses. Another industrial application was for the United States Postal Service, which adopted POSTNET barcode in 1982 as a way to automatically sort mail based on zip code.
How are barcodes used in industrial applications?Barcodes are widely used in manufacturing and quality control applications for industrial inspection. Linear or one-dimensional (1-D) barcodes represent data by varying the widths and spaces between parallel lines. 1-D barcodes are commonly used on products for traceability and sorting. Machine vision verifies that the barcode matches the product that it is printed on. Popular codes include: UPC, EAN, Code 39, Code 93, Code 128, Codabar, Interleaved 2 of 5, Pharmacode, BC412, Postnet, Planet, OneCode, RSS14 (Limited, Composite, Expanded).
Although many 1-D barcodes are still commonly used, two-dimensional (2-D) symbols using rectangles, dots, hexagons and other geometric patterns also evolved. While 2-D systems use a variety of symbols, they are generally referred to as barcodes as well. 2-D matrix codes are widely used across many industries for part traceability and process control. The codes are popular for their small footprint, built-in error correction and large data capacity. Popular codes include: Data Matrix, QR, MicroQR, and PDF 417.
Image-based readers are able to view the entire barcode, not just a single line. This lets them use advanced algorithms to overcome issues with blurry or damaged barcodes that cause problems for laser scanners. Image-based readers can also read barcodes in any orientation and they can read 2-D symbols such as Data Matrix and QR codes.
A Data Matrix code is a two-dimensional matrix barcode consisting of black and white "cells" or modules arranged in either a square or rectangular pattern. The most popular application for Data Matrix is marking small items, such as electronics components, due to the code’s ability to encode fifty characters in a symbol that is readable at 2 or 3 millimeters squared and the fact that the code can be read with only a 20% contrast ratio.
A QR code (abbreviated from Quick Response code) is a type of 2-D matrix barcode first designed for the automotive industry. More recently, the system has become popular outside of the industry due to its fast readability and comparatively large storage capacity. The code consists of black modules arranged in a square pattern on a white background. Its use has become popular in commercial tracking, entertainment and transport ticketing, product marketing and in-store product labeling. Many of these applications target mobile-phone users (via mobile tagging).
Another purpose that ID readers serve is Optical Character Recognition, or OCR. OCR is the mechanical or electronic translation of scanned images of handwritten, typewritten or printed text into machine-encoded text. At times, an industrial inspection system needs to read letters and numbers on a part instead of, or in addition to 1-D or 2-D barcodes. An example is date codes and lot codes printed on products that provide critical expiration and traceability information. OCR is based on pattern matching and so can be applied to a diverse range of verification applications outside of character reading. Often manufacturers will use OCR to build a library of parts that can later be identified and sorted.
Many industries uses bar codes and data matrix codes for identification, including defect detection and reject tracking for high speed applications in automotive, consumer, electronics, packaging and pharmaceutical industries. Identification applications include:
Challenges for Industrial IdentificationIdentification encompasses a range of machine vision applications that involve reading printed characters and decoding 1-D or 2-D symbols on products. For traceability of production parts, verification of product lots or grading of print codes, you’ll need identification tools that are designed for accurate results in the toughest of manufacturing environments.
Direct part marking of data matrix codes presents many challenges for industrial identification. With a range of printing methods available, from direct etching and stamping to laser scribing and peening, direct part marking on metal, plastic and other materials offer manufacturers extensive printing flexibility together with variation in print quality.
To meet this challenge, your application for part identification will need robust identification tools that can handle the wide variation in print appearance and part position. It is also important to receive a grading of printed codes that allows manufacturers to detect and correct deteriorating print quality.
Many industries are using 2-D matrix technology to track parts along the assembly process and throughout the product life cycle. In the automotive sector, for example, 2-D tracking is used for error-proofing to ensure parts are assembled in the correct order. In pharmaceutical manufacturing, product codes must be tracked within the supply chain to ensure customer safety. Verification of print quality on these packages is also important to ensure future readability.
What to Look For in an ID ReaderWhen researching the functionality of an ID reader solution, it is important to choose an affordable solution for a range of identification and quality control applications.
Look for one that handles both 1-D and 2-D tracking and also allows manufacturers to combine tracking with other inspection tasks, such as character reading, validation and verification, to ensure all product markings match and are readable when they leave the factory floor.
Look for OCR tools that can read a variety of printed characters and symbols under equally challenging conditions. With OCR, make sure new font variations can be quickly trained and saved to a pattern data base. Also, check that similarity scores are provided for the character verification process to indicate match quality. Finally, your ID reader solution should include embedded software and processing and be quick to set up and deploy.
About Teledyne DALSA's Machine Vision Products and ServicesTeledyne DALSA is a world leader in the design, manufacture and deployment of digital imaging components for the machine vision market. Teledyne DALSA image sensors, cameras, smart cameras, frame grabbers, software, and vision solutions are used in thousands of automated inspection systems around the world and across multiple industries including semiconductor, solar cell, flat panel display, electronics, automotive, medical, packaging and general manufacturing. For more information, visit www.teledynedalsa.com/mv . Sources:
Bar Code 1 http://www.adams1.com/history.html
Barcoding.com, “Barcodes Sweep the World,” by Tony Seideman, http://www.barcoding.com/information/barcode_history.shtml