Scan a barcode. Sounds simple — but before you can scan, there are many decisions to be made. Let’s start with selecting the right data capture technology for the job. Here are your choices:
- Laser Scanners
- Linear Imagers
- Area Imagers
- RFID
Laser Scanners
Pluses:
• Excellent for long range scanning
• Very bright, coherent spotting beam
Minuses:
• Oscillating mirrors make them less reliable
• Not as effective in reading damaged or poorly printed labels
Best Applications:
• Scanning linear codes on high shelves in warehouses and distribution centers
Standard laser scanners read bar codes with a laser beam in conjunction with oscillating mirrors to automatically move the beam back and forth across the code. Laser engines come in a variety of configurations (e.g. standard range, wide angle, high density, long range, and high visibility) to meet the needs of different applications. The major advantage of laser scanners is range: they can read bar codes from several feet away. In fact, if the symbol is printed large enough, the laser can read it from as far as 35 feet (10.7 meters). For applications involving a forklift operator in a warehouse, the ability to read a bar code without having to repeatedly get off the forklift is a distinct advantage.
On the downside, lasers tend to be more expensive than linear imagers and have moving parts (the oscillating mirrors) that wear out, often necessitating the replacement of the entire scanner. Laser scanners are available in handheld or fixed-position models. Handheld units generally operate at the lower end of scanning speeds (35-100 times a second) because the symbol being scanned is usually stationary. Fixed position scanners for conveyors operate at higher speeds (600-1800 times a second) and are fast enough to read the label before or as it moves past the scanning area.
Linear Imagers
Pluses:
• Reliable, solid-state performance
• Excellent for reading poorly printed and damaged labels
Minuses:
• Cannot scan at extremely long ranges
Best Applications:
• Retail POS
• Inventory management and order picking
• Production line replenishment
The underlying technology of a linear imager is a charge-coupled device (CCD). These state-of-the-art components appear in a wide variety of products from simple scanners and image-capture devices, such as fax machines, to highly sophisticated devices such as video and digital cameras. In a linear imager, the CCD captures different levels of reflected light from the bars and spaces of a bar code and converts them into a video signal.
A linear imager’s light source is provided by LEDs (light emitting diodes). Their low power consumption and long life means that the light can be on all the time, eliminating the need for a trigger— although some scanners do incorporate triggers and sleep/wake modes for power saving, especially when connected to battery operated devices.
Since linear imagers are solid state with no moving parts, they are inherently more reliable than laser scanners, which use fast-moving mirrors to move a beam across the code. To read a bar code, a linear imager illuminates it with light from the LED and uses a lens to focus the image of the bar code onto the CCD component. The simplest reading process identifies the peaks and troughs in the signal and applies decode algorithms to retrieve the bar code data. This is performed by the scanner’s analog-to digital converter and software running on the processor. The speed of the processor and efficiency of the software largely determine how fast this happens and how “snappy” or responsive the scanner feels to the user.
Area Imagers
Pluses:
• Provide omni-directional reading of codes (eliminates the need to reorient labels to read them)
• Reads virtually any symbology, including 2-D codes
• Captures signatures, proof of delivery
• Can take pictures of damaged cartons for proof-of-condition claims
Minuses:
• Cannot scan at extremely long ranges
Best Applications:
• Shipping and receiving from 3PL carriers
• Work-in-progress
• Field service and parcel delivery
• Insurance
An area imager captures a “picture” of two-dimensional or linear codes and processes them using advanced decode algorithms. Area imagers provide omni-directional reading of linear bar codes, so reorienting the label for scanning is unnecessary.
Additionally, area imagers are the appropriate scanning technology for reading two-dimensional (2-D) codes. Two-dimensional codes carry much more information in a smaller space than linear bar codes, making them ideal for space-limited applications like printed circuit board manufacturing, healthcare, and parcel delivery. Area imagers can be produced using either CCD technology or more sophisticated CMOS technology, which uses far less power while providing advanced performance. CMOS-based area imagers are ideal for applications like portable data collection in warehouse, manufacturing, and distribution applications, where changing or recharging batteries in mid-shift reduces productivity.
Because area imagers capture an actual picture (e.g. a signature or damaged cartons), they are ideal for field service, proof-of-delivery, and shipping/receiving applications.
RFID
Pluses:
• Delivers truly automated, hands-off data capture
• Does not require line-of-sight to read tag
• Acts as a portable, dynamic database that can be read and updated anywhere along the supply chain
Minuses:
• Cost of tags
Best Applications:
• Cross-docking
• Inventory management
• Tracking along the supply chain
• Parts traceability/product genealogy
• Asset management
• Access control
RFID is currently a complementary technology to bar codes, but has the potential to replace them in certain supply chain applications. In the short term, combination bar-code scanners/RFID interrogators allow workers to work with both technologies using one device. RFID is similar in concept to bar coding, but instead of a printed label with static
information that requires line-of-sight scanning, RFID tags acts as a dynamic portable database. RFID does not require line of sight to read tags, speeding the process of data collection. Also many tags can be read with one sweep of the read field. RFID tags/labels can be attached to virtually anything—from a vehicle to a pallet of merchandise. In addition, because the technology is difficult to counterfeit, RFID provides a high level of security.
