QR Code - abbreviated from Quick Response Code - is the trademark for a type of matrix barcode (or two-dimensional code) first designed for the automotive industry. More recently, the system has become popular outside of the industry due to its fast readability and large storage capacity compared to standard UPC barcodes. The code consists of black modules arranged in a square pattern on a white background. The information encoded can be made up of four standardized kinds ("modes") of data (numeric, alphanumeric, byte/binary, Kanji), or by supported extensions virtually any kind of data.
Invented by the Toyota subsidiary Denso Wave in 1994 to track vehicles during the manufacturing process, the QR Code is one of the most popular types of two-dimensional barcodes. It was designed to allow its contents to be decoded at high speed.
The codes are used frequently in the United Kingdom and the United States; QR usage is growing fastest in Canada and Hong Kong. Their use was formerly mostly confined to industry, but in recent years consumers have grown used to seeing them in consumer advertising and packaging, because the dissemination of smartphones "has put a barcode reader in everyone's pocket" for the first time.

Storage

The amount of data that can be stored in the QR Code symbol depends on the datatype (mode, or input character set), version (1,...,40, indicating the overall dimensions of the symbol), and error correction level (L[ow], M[edium], Q[uality], H[igh]). The maximum storage capacities occur for 40-L symbols (version 40, error correction level L), and are as follows (where character refers to individual values of the input mode/datatype, as indicated):

Numeric only

Max. 7,089 characters (0, 1, 2, 3, 4, 5, 6, 7, 8, 9)

Alphanumeric

Max. 4,296 characters (0–9, A–Z [upper-case only], space, $,%, *, +, -, ., /,:)

Binary/byte

Max. 2,953 characters (8-bit bytes)

Kanji/Kana

Max. 1,817 characters



QR Code Size Decision Factor


The size of QR Code is decided by determining a symbol version, based on data capacity, character type and error correction level, and by setting a module size, based on the performance of the printer for printing or the scanner for reading.



Symbol Version

The symbol versions of QR Code range from Version 1 to Version 40. Each version has a different module configuration or number of modules. (The module refers to the black and white dots that make up QR Code.)

"Module configuration" refers to the number of modules contained in a symbol, commencing with Version 1 (21 × 21 modules) up to Version 40 (177 × 177 modules). Each higher version number comprises 4 additional modules per side.

Each QR Code symbol version has the maximum data capacity according to the amount of data, character type and error correction level. Check the maximum data capacity for each version.

In other words, as the amount of data increases, more modules are required to comprise QR Code, resulting in larger QR Code symbols.


Error Correction

QR Code has error correction capability to restore data if the code is dirty or damaged. Four error correction levels are available for users to choose according to the operating environment. Raising this level improves error correction capability but also increases the amount of data QR Code size.

To select error correction level, various factors such as the operating environment and QR Code size need to be considered.
Level Q or H may be selected for factory environment where QR Code get dirty, whereas Level L may be selected for clean environment with the large amount of data. Typically, Level M (15%) is most frequently selected.

QR Code Error Correction Capability*

Level L

Approx.7%

Level M

Approx. 15%

Level Q

Approx. 25%

Level H

Approx. 30%

Data restoration rate for total codewords (codeword is a unit that constructs the data area. One codeword of QR Code is equal to 8 bits.)


Error Correction Feature

The QR Code error correction feature is implemented by adding a Reed-Solomon Code*to the original data.

The error correction capability depends on the amount of data to be corrected. For example, if there are 100 codewords of QR Code to be encoded,50 of which need to be corrected, 100 codewords of Reed-Solomon Code are required, as Reed-Solomon Code requires twice the amount of codewords to be corrected.

In this case, the total codewords are 200, 50 of which can be corrected. Thus, the error correction rate for the total codewords is 25%. This corresponds to QR Code error correction Level Q.

In the example above, the error correction rate for QR Code codewords can be considered as 50%. However, it is not always the case that codewords of not Reed-Solomon Code but only QR Code are susceptible to dirt and damage.QR Code therefore represents its error correction rate as a ratio of the total codewords.

(*) Reed-Solomon Code is a mathematical error correction method used for music CDs etc. The technology was originally developed as a measure against communication noise for artificial satellites and planetary probes. It is capable of making a correction at the byte level, and is suitable for concentrated burst errors.


Example of Symbol Version Determination

If there are 100 digits of numerical data, set the data type as "Numeric". Next, specify an error correction level. Then, find the intersecting value (the maximum data capacity) of the data type sequence and the specified error correction level. The value must be 100 or above, but as close to 100 as possible. If the error correction level is M (error correction capability of 15%), the code size is 29x29 modules, which corresponds to Version 3.


Setting Module Size

Once a symbol version is determined, the actual size of the QR Code symbol depends on the millimeter size of the module (one square area comprising QR code) to be printed.
The larger the module is, the more stable and easier to read with a QR code scanner it becomes. On the other hand, as the QR Code symbol size gets larger, a larger printing area is required.

It is, therefore, necessary to determine the module size of each application after considering all the relevant factors. It is recommended that QR Code symbols be printed as large as possible within the available printing area.


Version 1 QR Code (21 × 21 modules)

The module size is approx. 0.5mm2 The module size is approx. 1.0mm2




Printer Head Density and Module Size


The module size of a standard thermal transfer/direct thermal printer depends on the number of dots in the printer head.

For example, if the head density is 300dpi and each module is made up of 5 dots, the module size is 0.42 mm2. Increasing the number of dots improves printing quality, eliminates printing width or paper feed speed fluctuations, distortion of axis, blurring, etc, and enables more stable operations.

It is recommended for stable operations that each module is made up of 4 or more dots.



Printer and module size

Printer

Head density

4-dot configuration

5-dot configuration

6-dot configuration

Laser

600dpi
(24dot/mm)

0.17mm

0.21mm

0.25mm

360dpi
(14dot/mm)

0.28mm

0.35mm

0.42mm

Thermal

300dpi
(12dot/mm)

0.33mm

0.42mm

0.5mm

200dpi
(8dot/mm)

0.5mm

0.63mm

0.75mm


Scanner Factors

Each scanner has its own readable module size limit. The scanner resolution represents this limit.

For example, if a QR Code symbol is printed with a 600 dpi, 4-dot printer, the module size is 0.17mm. A scanner resolution of less than 0.17mm is required to read the symbol.

Small printing in the limited area with a higher head density printer can be useless if the reading limit of the scanner is exceeded. Consider the scanner to be adopted before determining the module size to be used.

The scanner resolution of our products is shown below.

Scanner type

Resolution

High resolution type

AT10Q-HM

0.167mm

GT15Q series(for US/for EU ASIA)

Standard type

BHT-760QWBG-CE

0.25mm

BHT-600Q series

AT10Q-SM

Camera type

QD20

Variable according to lens

Decode software

QRdeCODE

Variable according to iPhone



Securing Margin


When the symbol version and module size are determined, the size of the QR Code symbol is determined. The QR Code symbol area requires a margin or "quiet zone" around it to be used. The margin is a clear area around a symbol where nothing is printed. QR Code requires a four-module wide margin at all sides of a symbol.

Margin of QR Code

Four-module wide margin is required around a symbol.


Example of Calculating QR Code Area

Below is an example of calculating the total QR Code area including margin.

(Example) Creating QR Code to encode 50 alphanumeric characters

  1. Specify the error correction level as the standard "M".
  2. Obtain a version from the Version and maximum data capacity table (find the intersection of alphanumeric characters and Level M). → Version 3 capable of storing 50 or more characters. (Version 2 with Level M holds only 38 characters.)
  3. Use a printer with 400 dpi resolution. → 0.254 mm when printed with 4-dot configuration.(Equation: 25.4 mm/inch ÷ 400 dpi × 4 dots/module = 0.254 mm/module)
  4. 4. Version 3 = 29 modules, therefore, the size of QR Code is 29 modules × 0.254 mm/module = 7.366 mm.
  5. Secure a four-module wide margin. 7.366mm + 0.254mm/module × 8 modules = 9.398mm

In other words, the required QR Code area is 9.398mm2.


If QR Code Area gets Too Large

If the QR Code area obtained in the process above does not fit the printing space, consider the following three points.

  1. Decrease the symbol version
  2. Make the module size smaller
  3. Split the QR Code symbol

Information is quoted from http://en.wikipedia.org & website of DENSO WAVE INCORPORATED .

QR code is registered trademark of DENSO WAVE INCORPORATED .

Home SIE Technologies Implementation Contact Us
About us 2D Barcode OR Code
Mission RFID RFID
Core Aspects What's New
Privacy Policy Events
Copyright © 2012 Stechz Innovation & Engineering Limited. All rights reserved.