QR Code Overview
The QR or Quick Response Code is just now hitting the shores of North America but it has been widely used in Asia for many years. Here in America we are becoming familiar with QR Code mainly in mobile marketing applications—magazine and newspaper ads, business cards and the like—but QR Code has many other applications. In Japan QR Code is mainly used for automotive and logistics applications.
QR Code has been around for over 15 years
Because we are late adopters, we think of QR Code as new technology, but in fact it has been around for over 15 years. QR Code was invented in Japan by Denso-Wave Corporation in 1994. It was approved as an AIM international standard in 1997, assigned an ISO international standard (ISO/IEC18004) in 2000.
QR Code has impressive data capacity…
Max. 7,089 characters
Max. 4,296 characters
…and it is also very robust, using the Reed-Solomon error correction methodology which allows the user to define the level of error toleration.
QR Code is public domain thanks to Denso-Wave Corporation
Like most (but not all) symbologies, QR Code is an open source. Although Denso-Wave Corporation invented the QR Code and owns the patent rights, it has publicly chosen not to protect those rights, thus making the QR Code “open”.
QR Code is not a single version symbology—in fact there are 40 versions of it which vary according to the number of modules, the error correction level, whether the data is numeric only or full alpha-numeric, and other factors.
For example, Version 1 is 21 x 21 modules and has a data capacity of 153 data bits, 41 numeric-only characters, 25 alpha-numeric characters or 17 binary characters.
Version 40 is 177 x 177 modules and can encode 23,648 data bits, 7,089 numeric-only characters, 4,296 alpha-numeric characters or 2,953 binary characters.
QR Code symbol size is a function of many factors
This still doesn’t translate directly to symbol size because the modules size can vary, depending upon the resolution (pixel or dot size) of the printer, and how many dots are used to comprise a module. A thermal transfer printer with a 203 DPI resolution will have a dot size of approximately .005” so a 4 dot module will be .020” or approximately .5 mm.
What is the right size for a QR Code? Not a simple question to answer. A number of factors are involved. In general, a high resolution scanner can resolve a QR Code with a module as small as .170mm; a standard resolution scanner can resolve modules of .25mm. But mobile devices are not scanners—they are digital cameras of various types. Their ability to read a QR Code depends on the optics of the camera. Smart phones contribute yet another variable: the decode algorithm or software onboard, and here again, the ability of a smart phone to read a QR Code depends on the smart phone manufacturer, optics and software. Generally speaking newer smart phones are better, but QR Codes are not unformly visible to all smart phones. A test chart for scanners and smart phones is available here.
QR Code is mostly a marketing tool in the US as of this writing, but that will change soon. These changes will make QR Code performance—and therefore quality—an ever more important consideration. More about that in subsequent articles.