The technology used to read barcodes is relatively uncomplicated, but there's little info designed for the novice. That is intended to be an introduction to the scanning, processing and presentation of barcode facts.
Scanners
A scanner is a device that converts the image of a barcode into electrical pulses. You can find four simple methods for doing this: contact wands, active non-contact (AKA laser scanners), and passive non-contact, which is often cameras or linear CCDs (charge coupled devices). Most of these devices have comparable outputs, strings of electrical pulses that mimic the white/dark and width from the bars. Apart from cameras, a scanner will invariably contain a light source, either LED or laser.
Wands will be the simplest, but have the most limitations. A wand has a light source, focusing lens along with a light detector. It has no moving parts, that makes it probably the most rugged of scanners, but it also indicates the operator should move the wand on the code. This takes some practice. The 2nd important limitation: the wand have to touch the barcode. A barcode within plastic case or an overly-thick wrapper cannot be read with a wand.
Laser scanners have moving parts that are quickly damaged. They include a laser light, some mirrors and a detector. One or more of the mirrors moves, which allows the laser beam to scan a code. Several mirrors can redirect the beam in many directions. A lazer is very thin which allows the scanner to learn barcodes at long distances. They can also make multiple scans of the identical code in very short periods. These properties make them ideal for stores and factory use the location where the distance between your barcode along with the scanner can incredibly from scan to scan.
CCD scan engines will contain a light source (usually LED), lenses along with a linear CCD. The barcode is illuminated and also the lenses focus the image on the CCD. Scanning is performed by reading the reading the charge levels on each one of the CCD elements. CCD detectors can have 1024, 2048 or even more elements. Being a wand, a CCD scanner has no moving components. These scanners do not make get in touch with using the barcode, for them to function at a distance. Due to the really need to focus the barcode's image about the CCD strip, the distances inside which a CCD scanner works is a lot more limited than for a laser scanner.
Camera scanners use an array of CCDs and lenses, plus some them add a light source. They've lower-resolution detectors, which limits their use to unique 2D matrix barcodes, unless close-up focusing can be an choice about the camera. Webcams and cellphones can be utilized in this way.
Light to data
The output of a scanner is really a string of electrical pulses. Typically two voltages are used for the pulses, a high-state and zero. If viewed using the appropriate equipment, the high & low states would map directly to the black & white bars of a code. The conversion is done by the main reader, or perhaps in some applications by way of a keyboard wedge.
The pulse string is processed in many methods. The very first is a appear at the lengths with the pulses. Many barcodes use constant width bars and spaces, however the most common barcode, the UCC/EAN code, uses four widths. Every barcode type includes a font. A lot of them also have guard bars, which indicate the location where the code starts and stops. The guard bars might also give a clue regarding the direction with the scan. The UPC barcode uses three bars at the ends and five at the center. The guard bar patterns are not employed for numbers or characters. So by noting the locations of the guard bars, the scanner can certainly combine scans with the left and proper sections to produce a complete code.
Once the type of barcode may be identified, the pulse string is broken into groups of bars that form characters. When decoding a UPC, each character is four bars: 2 black, 2 white.
Once each and every character may be identified, there might be a check sum calculation to ensure the complete code is valid. The UPC barcode performs a calculation determined by every digit's position and compares that towards the last digit from the code.
Data to details
The converted information is now in the digital form. This might be a coding pattern like ASCII or it might be keyboard codes. The former is standard for stand-alone readers, the second far more common in point-of-sale or office use.
Keyboard wedges that connect scanners to computers will use keyboard codes, therefore the computer accepts the input as though someone were typing the code.
A wireless reader can either store the digital codes or transmit them to a central system. Several handheld, portable readers contain small amounts of memory that can store 100-150 barcodes before they need to be connected to some type of computer to download. Connections can be via USB or a serial port. In almost all cases, specialized software is required to see the data. Wireless readers that transmit to some central system don't need data storage, but you are limited inside their range. This really is most useful in just a warehouse or even a factory.
Utilizing the data
If a barcode is just not routed to a central computer, it needs to be displayed inside a human-readable format. Devices that may do this are classified as portable data terminals (PDT).This can be a bad term, because only the portable part is true. A portable data terminal is really a free-standing barcode-reading system.
A PDT will contain a scanner, a processor, memory, storage along with a display. Frequently, they are actually laptop or palm computers that a scanner continues to be added. A few are purpose-built and optimized to see barcodes and translate that to useful, human-readable form. A PDT can contain tables or databases which allow it to find information about scanned codes and tell the consumer what they represent and how several there are.
A PDT is often incredibly expensive, since it has a lot of capabilities. Those based on laptops may cost many thousand dollars. Even palm devices can be $600-$1000 dollars once the scanner has been added. Businesses can integrate PDTs to their inventory systems, and several of the lower-cost devices can be put in the hands of all of their field personnel. Items utilized though servicing customers' equipment can be scanned on site and the info loaded in to the main inventory system later for billing and inventory management.
Some purpose-built PDTs are small enough and inexpensive enough for use as consumer devices. Given a scanner, storage and a display, consumers are able to use these devices to inventory their music, movie and book collections.
The inventories can be stored on their home computers or stored remotely, or both. Websites that appeal to collectors can frequently convert barcodes to far more useful data like titles, authors and composers. Small, pocket-sized devices created for portability can actually be carried at all times, and utilized to check new purchases against items already collected, simply by scanning codes.