Data Matrix

The Data Matrix code is one of the most well-known 2D codes. He was in the late 1980s in the United States by the Acuity Corp.. developed.

Applications

Today, this code is one of the most common types of 2D codes and is used for permanent direct labeling by laser in production ( eg printed circuit boards), with dot peen in the automotive industry, with analysis devices and instruments (chemistry, medicine), but also increasingly as a printed code image in the document handling ( tickets, franking the mail ) are used.

Appearance and size

The size of the square - at certain aspect ratios also rectangular - code image is determined from a large selection set, the symbol elements are square or round.

Error correction

The Data Matrix code exists in combination with two different error correction method. The method used initially used for error correction a convolutional code. This variant is referred to as ECC00 ECC140, with ECC for error correction code (English " error correction code " ) is and the number indicates the extent to which the data is stored redundantly in the code. Recently, the powerful Reed-Solomon algorithm is used for error correction. This variant is called ECC200. It is generally recommended to use only the current ECC200 version. All variant additionally use a CRC (Cyclic Redundancy Check ) algorithm for error detection.

The ECC 200 is based on the error correction code words of the code, each consisting of eight array cells. A matrix cell per code word (8 matrix cells in total), which is broken, destroyed, the code word. However, only one codeword is destroyed when all 8 matrix cells of the code word are destroyed. In the rectangular version of Data Matrix codes 3-14 erroneous code words can be corrected. In the square version 2-310 incorrect code words can be corrected. Each individual number of uncorrectable codewords is only valid for a matrix size (between 10 × 10 to 144 × 144 )

If the errors are distributed so that the destroyed areas to destroy 25% of the code space while the number of permitted destroyed code words is not exceeded, an automatic correction is possible. If the errors are distributed so that a small code surface is destroyed, but many codewords are concerned, does the error correction is no longer (or only up to the defined degree of allowed code words destroyed ).

Standardization

The Data Matrix code is defined by the International Organization for Standardization ( ISO) standardized ( ISO / IEC 16022:2000 ). The Technical Report ISO / IEC TR 24720:2008 describes the application of the code in direct part marks (DPM - Direct part marking ). These standards provide a uniform basis and thus permit codes regardless of the manufacturer of the printer or the reader make and read.

GS1 uses the data matrix code and the result to be GS1 Data Matrix ( DataMatrix code would be technically correct with GS1 data structure). It is in this case the Symbologienorm of the data matrix, the ISO / IEC 16022, applied. In addition, the first encoded character is always the special character FNC1. After FNC1 mark follows a defined data structure, which is referred to as the Application Identifier GS1. This Application Identifier can also be encoded in the GS1 -128 or GS1 Databar Code.

GS1 is an organization that is registered as an IAC ( Issuing Agency ) in accordance with the ISO / IEC 15459-2 at the official registry for IAC 's. The registrar is the Dutch standard NEN Institute. IAC 's can build with the help of these registry internationally unique article number systems and serial number systems. The whole thing happened under the umbrella of the ISO. Other IAC are ODETTE, HIBC, EDIFICE, etc. GS1 itself is no standardization organization, but an organization that ensures that there are globally unique number ranges within the scope of retailing. GS1 The participants of the GS1 System financed through fees for the allocation of manufacturer numbers.

Since the GS1 Item number system is very good for the retail of consumer goods, especially food fits, there GS1 is dominant. In other industries (automotive, aerospace, electronics, etc.) other unique ISO number systems are used that also use the Data Matrix code as a data carrier. A Symbologieschutz by special characters such as FNC1 character does not exist. The use of FNC1 characters or other experts is free will. However, it is strongly recommended that the requirements according to ISO / IEC 15418 to be observed (reference to ANSI MH10.8.2 ), to avoid confusion and mistakes. Demfolgend FNC1 is only with GS1 data structures used during the macro represents 06 code word 237, in accordance with ISO / IEC 15434, a unique identifier for the other ISO unique data structures.

Compared with one-dimensional bar codes

When data matrix code the information is encoded in a very compact area than square or rectangular pattern of dots. When reading a Data Matrix codes are no longer two different bar widths in the sequence are uniquely determined, as in the one-dimensional bar code (1D code), but the arrangement of equal points within the boundary ( the search pattern ) and the grid of the matrix. The dots are black or white boxes that connect to each other, or round points with gaps in between. But this uniform symbol size and the solid symbol spacing make the reading of the image and decoding the information much more secure and the code in the extension considerably more compact. Since the data matrix code also provides a method of error correction, it displaces the bar code, which usually supports only the detection of a single fault, in many applications.

Construction of the code image

The Data Matrix code consists of four or five main components:

The Data Matrix code 144 × 144 ECC 200 (plus pattern and alignment patterns ) can be up to 1556 bytes, and therefore encode 3116 numeric ( 3.5 bits per character ) or 2335 ASCII characters ( 7 bits per character).

Readers

In contrast to the 1D code a digital camera is used in the 2D code ideally. The code image only needs to be in the camera window, the orientation towards the field of view is indifferent. This can be automatically mapped to the data matrix code without movement of the device or optics. Reading the codes is normally at rest or in uniform motion object, wherein a single image is captured and analyzed. Higher speeds during recording are made possible by the use of line scan cameras.

The camera captures the information in two dimensions and a software evaluates the image. Therefore, 2D codes need to be extensively illuminated by a light source. The light reflected from the 2D code light is then imaged in an " image plane ", for example, a CMOS sensor, sharp.

Many camera phones are equipped with a code scanner. For example, you can simply read an encrypted in a data matrix code phone number or website address.

Line scanner are uncommon and not as secure in the image of the code image.

Pressure requirements

The demands on the print quality of matrix codes are defined in ISO / IEC 15415. This standard covers the respective Symbologienorm, here ISO / IEC 16022, with a. Among others, thus demands on contrasts and distortions defined matrix.

It should be noted that the data matrix code in accordance with ISO / IEC 16022 for direct marking (laser, dot peen, etc.) is not specified.

Since this is in the industry is a typical application of the Data Matrix code is 29158 print quality requirements developed by the ISO / IEC TR, which closes this gap. The Technical Report ISO / IEC TR 24720 describes the different methods for direct identification. One aspect of this is the use of Data Matrix codes. Another similar application of the Data Matrix code is described in DIN V 66401.

In particular, nailed codes ( dot peening ) are a robust marking which remains legible for the life of labeled products.

Similar codes are the QR- code according to ISO / IEC 18004, the Maxi code according to ISO / IEC 16023, the Aztec Code, the Code and other Mesa, partially proprietary code.

Examples of use

The German Post AG utilizes franking codes of size 22 × 22 and 26 × 26 for the Internet brand codes of size 26 × 26, for the product Stampit codes of size 32 × 32, for the product Frankit the size 36 × 36 and news post with edge lettering codes of size 52 × 52

The Swiss Post uses the data matrix code - including for the franking of mass mailings. Under the product name "PP Easy " ( a static code for the entire mission ) and "PP Business » ( dynamic code, each element of a program receives individual information ) these franking solutions are offered. In the Data Matrix Code this information to the sender (transfer of the shipment ) and the handling of returns included. In the case of "PP Business », the customer ( the shipper ) additional characters available that he can use for their own information.

It is generally described with the international standard ISO 22742, the labeling of products with codes. It come of it ISO compliant data structures are used as well as codes that are specified in an ISO / IEC standard as the data matrix code.