An Evaluation Of 2D Barcodes In Document Processing Applications

Many documents to be processed electronically contain bar codes to encode important information that is extracted through software decoding of bar codes. There are a number of issues to consider when choosing a bar code symbology. The biggest distinguishing characteristic to consider is whether a linear (1D) or 2-dimensional (2D) is the symbolism that will be used. 1D symbologies, as its name implies, usually consist of modulation width of the bars and spaces that encode the information of the user. There is no information in the vertical dimension of a symbol 1D. 2D symbologies encode information in two dimensions of the symbol and as a result, have much higher density of data. 2D symbols often used a grid of cells for possible positions, which is an cellmates, either white or black.

This article will focus on the use of symbols in 2D document processing applications because of the important data density 2D advantage of the symbols more 1D symbols. In particular, we will compare the relative merits of three popular public domain 2D symbologies: Data Matrix, QR Code and Micro QR Code. After a brief overview of each of symbolism, let’s compare them based on their density of data, error correction, and the relative speed of processing.

Data Matrix

Data Matrix symbols using a set of square cells ranging in size from 10 to 10 the network up to 144 by 144 network. A 1-cell area is required around the symbol. In addition, rectangular sizes are also available. Each symbol consists of a fixed “L” pattern that is used to find, together with a clock on the hillside along the opposite sides of the “L”. In addition, there are tracks of large internal clock for Data Matrix. These fixed locations not encode all the information. They are present to determine the symbol as an array of data and helps to decode the software. The remaining sites contain either a black or white squares, depending on the information to be encoded.

QR Code

QR Code symbols also employ a variety of square cells ranging in size from 21 by 21 network up to 177 by 177 network. A 4 cell area is required around the symbol. To find help, QR Code symbols contain 3 finder patterns at 3 of the 4 corners. In addition, there are internal alignment of patterns, patterns of clock, as well as the most comprehensive information about the symbols that gives the size of the code.

For data applications that require smaller amounts of data, is a derivative of the version of QR Code called Micro QR code that can be encoded to 35-digit numerical in less space than the corresponding QR Code. It has 4 different sizes square: 11 of 11, 13 by 13, 15, 15 and 17 x 17. Each requires a size of 2 cell area around the symbol. Search engine contains only 1 pattern, with limited clock pattern and format of information.

Density of data and error correction

Data Matrix has a clear advantage in data density over QR Code. This is especially true for small amounts of user data. This is due to the fact that there are fewer fixed cellular sites. Not devote much space to search for patterns, and does not contain any formatting information. Micro QR code was designed to address the issue of the density of data and is comparable in size to the array of data to the data content.

All 3 types of symbols used Reed Solomon error correction to detect and correct errors due to damage or symbol image issues. The number of detecting and correcting errors is determined by the number of extra error correction code in the symbol that are above and beyond the code used to encrypt the data.

The data capacity of a certain size symbol is a function of the amount of error correction general, and the data itself. Data Matrix uses a standard error correction that is not your choice. The percentage of error correction code generally ranges from 62.5% for the smallest symbol to 28% for large symbols. By contrast, QR Code has 4 different levels of error correction that allow an approximation of the ability to recover from 7%, 15%, 25% or 30%. Micro QR code varies the choice of the amount of error correction for each of the 4 permitted lengths. The smallest only allows the detection of errors, while the largest allowed up to 25% capacity for recovery.

The amount and type of user data will dictate the size of the symbol is necessary. In addition, the Micro QR Code and QR Code, the amount of error correction used in the size factor, too. The following table summarizes the relative size and the ability to correct errors of 3 symbols shown above.

Symbolism - relative size (with quiet) / general error correction (%) / Max correct errors

Data Matrix - 1.00 / 58.3 / 3

QR Code - 3.70 / 65.3 / 8

Micro QR code - 1.33 / 50.0 / 1

The choice of the amount of error correction code used in the QR and Micro QR Code is dependent on the application. In cases where the size is a problem, one might be tempted to reduce the amount of error correction overheads. This can reduce the rate of the symbol if you read the bar code can be damaged or if the environment of images makes it more difficult to achieve “ideal” image. Bar codes on the gentle curve of the packages that symbol, as well as the bright ribbon on the symbol that can cause a specular back to the camera are examples of how the codes can be damaged. In general, if space allows, for optimum read rates, normally one must choose the maximum allowable capacity for correction of errors.

On processing speed

Real-time applications where time to decipher an image is important, one must also compare the symbologies of the speed with which it can be decoded. The most time-consuming part of the decoding of a bar code in a big picture and is generally busy searching for the symbol. The more singular the search within a pattern of bar code symbol, the easier it is to locate within an image occupies. This reduces the processing time. Conversely, if a bar code symbology does not provide a single search engine, more time will be spent in search of her.

QR Code and Micro QR code has a significant advantage on Data Matrix, because the only search engine patterns within the symbols. QR Code is the best of 3 options because it includes 3 models finder, each of them is capable of being used to find the symbol. Data Matrix is the “L” finder pattern fixed lines and watch. Unfortunately, these are not terribly unique patterns in ways that many text areas are surrounded by boxes. In addition, both QR (version 7 and above) and Micro QR codes have the format of the information on the symbol to let you know the size of the symbol and to confirm that are in a real symbol. Data Matrix does not explicitly contain the data format, providing only a clock track of the opposite sides of the symbol of the “L” corner.

One way was occupied scanned at 200 DPI and a unique example of the 3 symbols of bar code has been added to the picture with each symbol using 25 thousand cells. Then, in 3 separate passes, Volo ™, a software decoding codes toolbars Omniplanar ®, was used to decode each symbol. With each pass, only one type of symbology activated. The following table summarizes the time it took Volo to cast the result of completely finished decoding and processing the image. Both QR Code and Micro QR decoding were 3 to 4 times faster than the Data Matrix decoding. This is almost entirely due to good pace in the search for Micro QR QR and symbols.

Symbolism - Issue Time (msecs) / Total time (msecs)
Data Matrix - 30.8 / 74.5
QR Code - 7.2 / 23.4
Micro QR code - 7.6 / 21.9

Abstract

When deciding what type of 2D symbology to use the applications in the paper, one must consider the density of data, correcting errors and processing time. In applications where the size of the symbol should be kept to a minimum, both Data Matrix and Micro QR code are good options. When the processing speed is of paramount importance, Micro QR Code and QR Code are both better choice Data Matrix view of its good search of patterns. In applications where both a symbol of size and speed of processing are important, Micro QR Code is the best option. However, the greatest possible number of Micro QR Code can only store 35-digit numbers with minimal error correction (maximum of 3 errors). At the highest level of error correction, the data capacity is reduced to 21-digit numbers (maximum of 7 errors).