Barcode reader

A barcode reader is a data acquisition device that can read various barcodes and share. The recognition of these bar codes is done purely optical with either red or infrared light. Each bar code reader comprises the actual reader unit and the downstream decoder. While this in reading pens usually two devices ( it is also read with pins integral decoder ), almost all other types of device, the decoding unit is integrated with the reading unit. Almost all types are now available on the market as stationary, as cabled hand-held scanner or a mobile recording devices (eg inventory terminals with integrated barcode scanner).

Device types

Wand

The wand is moved by hand directly on the bar code. In its optical head, a light source, typically a light emitting diode, and a light-sensitive sensor are housed. The light from the LED is reflected by the different degrees of bars and spaces of the bar code. A decoder receives these different light / dark signals so deciphers the barcode and transmits the useful information contained therein to the downstream system (eg PC, POS, etc.).. It is one of the direction and speed forth the smoothest motion on the bar code required to decode the signal without errors. While the actual technique of detecting stayed the same light and dark reflections, wands are rarely or only for very specific applications used since the late 1990s because of their disadvantages in the application.

Advantages:

• Low cost (about 10-80 euros )
• Relatively high robustness ( pin mostly in metal housing, no moving parts or delicate optics )
• Very small unit, since the decoder is usually housed separately

Cons:

• Poor reading results in damaged codes, or those of low pressure or surface quality
• Low tolerances in reading speed (especially their variation ) and reading angle
• By repeated sweeping of the same barcode, the barcode can be mechanically damaged (especially in bar codes that have been created with thermal printers )
• Compared to scanners relatively uncomfortable, slow capture
• Especially for larger bar codes, some exercise is necessary to capture the code in full width.
• Often separate decoder needed
• Do not capture possible new, two-dimensional barcodes

Swipe reader for barcode cards

Instead of leading the reader through the barcode reading unit is resting on a bar code reader and a printed with a barcode card is swiped through the reader. In this case, a separate decoder is also required, which can also be incorporated into the reading unit. These readers are cheap. The disadvantage is that you can only read bar codes that are printed on cards with specific dimensions.

Barcode card reader are often used for low-cost access control or time and attendance systems. To protect the barcode before simple copy and so to give the cards a certain security against forgery, the barcode can be covered by means of special plastic sheets that are only permeable to infrared light, so it is not visible with the naked eye or with a copy machine, but can be read by an infrared reader.

Advantages:

• Easy to use, since the card has to be pulled through a slot, so good for self-service
• Small dimensions
• Low cost
• Decoder usually integrated in the housing

Cons:

• Reads bar codes of cards with a set format and is therefore only suitable for very special applications
• Collect new, two-dimensional bar codes is not possible

CCD scanner

When CCD scanner is a very flat line section of the bar code is scanned over its entire width at one time. To this end, the code will be illuminated by LEDs. The barcode reflected depending on the lightness or darkness of a CCD or photodiode array. A decoder decodes from this the bars and spaces of the bar code and thus the information contained therein. The distance from the barcode may be up to about half a meter, depending on the LED intensity, optics (depth ), size of the bar code and the ambient light a few centimeters.

Advantages:

• Easy to use even for beginners
• Rapid scanning of the bar code " at your fingertips "
• By repeated decoding the code in a read operation, the read reliability is increased
• No moving mechanical parts
• Relatively high resolution

Cons:

• There is not a contact reader, but the possible reading distance is relatively low
• Collect new, two-dimensional bar codes ( 2D codes ) is not possible

Laser scanner

One or more laser beams are directed onto the bar code and guided linearly via a vibrating mirror, a mirror wheel, or other optical systems at high speed across the barcode. The more or less reflected by the bar by the bright and dark bars light is then detected by an optical system and converted into electrical signals by means of photodiode and analyzed.

Advantages:

• High reading distance possible
• Reading possible even under difficult lighting conditions
• Easy to use even for beginners
• High reading speed

Cons:

• Collect new, two-dimensional bar codes is not possible
• By mechanically moving components increased susceptibility

Linear laser scanner

In simpler laser scanners, the light spot passes over the barcode always in the same angle. To fully capture the barcode whose lines must be run in approximately 90 ° angle to the reading direction or aligned according to the operator. For the viewer creates a single-line scan line.

Laser scanner with a linear grid

Linear scanning is achieved by a slight displacement of the swinging point of light from left to right in the vertical direction. This is done automatically by the system and a high speed. For the viewer, creating a field of several parallel lines. This technique both the size of the scan area ( accurate targeting is less important) as well as increased tolerance to minor damage in the barcode ( as these can be reconstructed fall through the variation of the cut less weight or ).

Omnidirectional Laser Scanner

Staggered or rotating mirror or prism systems generate grid lines, so several lines that emphasize the reading field in mutually offset angles. In this way, a position the bar code is redundant, since it usually already allow five, arranged in a circle scanning directions, align the barcode at any angle to the direction of the light spot. For the viewer, creating a grid of many, overlapping itself, circularly arranged lines.

Laser scanner with rotating screen

In this further development of the omnidirectional scanning technique is caused by rapid rotation of the entire scanning field around the own center of a reading area, which is swept out by the spot of the laser beam in a very short time in virtually any angle. In this way, the entire bar code is detected without missing significant portions. Torn or damaged barcodes can be better reconstructed by the decoder software, an expense is recognized even faster, since the barcode is almost immediately recognized.

The information of the reflected beam can also be assembled in the decoder and so capture the entire contents of the code. A quality of a laser scanner, its scanning speed, that is, how many times the item passes over the bar code in a second. This frequency, depending on the requirements of the scanner, are between a few dozen to several thousand hertz.

The maximum distance of the barcodes to be read can be ( at totally reflecting barcodes ) with laser scanners 10 cm, 15 cm or more meters. Are used such scanners, for example, in high-bay warehouses to read barcodes from the forklift. The barcodes but this must also have an unusually high size.

Camera scanner ( imager)

The latest generation of barcode readers is referred to as " Imager ". You enter the barcode using a small camera. Then the captured image will be processed by digital image processing and the barcode digitally captured. 2D image scanner and CCD scanner used for detection and decoding of the image, a similar technique in which not only one, but a plurality (many ) of the displayed image, lines to be simultaneously detected in a 2D image scanner. Thus, it is possible to arrange the information in a two-dimensional area and to detect in a single step. Imagers are used by the built-in camera also to capture documents or passports, and thus offer eg at the box office a much enhanced functionality. Moreover, it is with the help of digital image processing also possible to use camera phones as readers in particular for 2D codes. Since 2D codes represent relatively much information in a small space, can in this way also smaller files (eg sound bites, promotional messages or extended product information ). For cost reasons, monochrome photo sensors ( CMOS, CCD, or similar. ) Are used in camera scanners often, which can be created only black and white photographs. Systems are also available with a color camera.

Advantages:

• Omni-directional scanning of code
• No moving mirror optics, so much more robust and space-saving

Cons:

• Relatively expensive technique
• Relatively low resolution 1D ( compared with 1D CCD scanner)

Handy scanner

Another new generation of so-called cell phone scanners. There are a number of mobile phone applications that make it possible, 1 - or 2- dimensional codes to capture and bar code with the digital camera of the mobile phone and the user display more information. In addition to the phone's camera is on the phone to an image processing application is necessary, which is responsible for the evaluation of the camera images. An example is the app Barcoo, which among other things based on the barcodes of food products represents the related nutritional information in the form of traffic lights (food traffic light).

Data transmission

The decoded data can be transmitted over different interfaces to the superior system then.

• A common use is the looping into the keyboard connecting cable of the computer usually by means of intermediate connector ( keyboard / wedge emulation). This has the advantage that no software changes are necessary because the computer does not recognize whether it is a manual or a read-in data entry. Note are only keyboard layout and the operating system used.
• Or the transmission is another external interface of the computer, a serial interface such as RS232 or RS485, a USB port or similar instead.
• Or the reader are an integral part of a data acquisition device, which relays the data, for example in a radio network (WLAN).
• As more wireless data transmission, in addition to proprietary radio technologies often also used Bluetooth.