LASER OR IMAGER?

Logistics Insight Asia, 1/5/2008

Deciding which bar code scanning technology – laser scanning or digital imaging – is right for your application requires careful consideration of a variety of factors.

Over the past few decades, bar code scanning has become the data capture technology of choice, enhancing processes in virtually every industry and market. Low-cost scanning solutions improve performance and reliability in a wide range of enterprise activities, and reap tremendous business benefits, including increased worker productivity, improved task efficiency, and reduced operationalcosts.

As scanning technology evolves and new bar code symbologies appear, industries have more choices in data capture solutions. Two competing, and sometimes complementary, data capture devices are the laser scanner and the digital imager.

When implementing a data capture system, technology customers should weigh the options carefully and give thoughtful consideration with respect to the needs of the application. Both laser scanning and area imaging are powerful technologies that afford numerous benefits for their appropriate markets.

LASER SCANNERS
In a laser scanner, the scanning optics system generates a laser beam and uses a lens to focus the beam. An oscillating scan mirror moves the beam back and forth rapidly across the target bar code to create a laser line which illuminates the bar code.

The collection optics system then retrieves the laser light reflected off the bar code and concentrates that light onto a photodetector. The collection optics also enables the scanner to reject external light that can interfere with the laser light.

Next, a photodetector transforms the reflected laser light into an electrical analog signal and converts the analog signal to digital data. The scanner’s decoder processes the digital data and applies a symbology algorithm to interpret the data. It then verifies the information via a check digit, typically the last digit of a bar code that tells the scanner whether it scanned the data correctly, and sends the data to the connected host.

Laser scanners offer a number of advantages for a multitude ofapplications:

• Laser scanners can effectively read bar codes even when the scanner or the bar code is in motion, enabling them to achieve excellent scanning productivity. For this reason, laser scanning is the preferred technology in high-throughput areas and in hand-held scanning scenarios.

• Laser scanners are generally less expensive than comparable imagers. The combination of low price and high productivity often makes laser scanning the better option in applications that don’t require reading 2D bar codes.

• Laser scanners can project a beam of light a long distance without diverging, achieving 50 percent more range than more expensive area imagers. This is advantageous in applications that require scanning range flexibility, such as forklift operations where packages are often located on high shelves or hard-to-reachareas.

• The laser line represents exactly what the scanner’s sensor sees, so the operator can intuitively aim the scanner properly to achieve quick decodes.

DIGITAL IMAGERS
A digital area imager projects LED light that illuminates the target bar code. Then, like a digital camera taking a picture, a lens projects the image of the bar code (and the area surrounding the bar code) onto a 2D array, and the light is converted to an electrical signal to construct the digital image.

Decoder software in the imager locates the bar code within the image, and processes its data using advanced decoding algorithms. Then, like the laser scanner, the imager verifies the bar code data via its check digit and forwards the information to the connected host. Among the benefits of digital area imagers in data capture situations:

• In addition to 1D bar codes, area imagers can read 2D bar codes, which can accommodate significantly more data. This is beneficial in situations that require symbols to encode more information, such as transportation and logistics, and tracking applications.

• Area imagers enable omni-directional reading of bar codes, eliminating the need to reorient labels to accommodate the scanning device.

• In addition to bar code decoding, some high-performance area imagers can capture and transfer images, enabling signature capture and other imaging applications like scanning documents.

• Area imagers can also read Direct Part Marking (DPM), a method of permanently marking a product or component so it can be tracked throughout its life.

Note: the class of products known as “linear imagers” capture only a single row of pixels within the image, which allows them to decode a 1D bar code, but not entire images or 2D codes.

MAKING CHOICES
Almost every market can benefit from the use of data capture technology. Following are just a few of these target markets and applications, some in which laser scanners prove advantageous, others more suited for digital imagers, and still others that canprofit by using either or both.

MANUFACTURING
The manufacturing market entails all the activities required to construct a product, including assembly, work in process, and error proofing of items ranging from tiny circuit boards to jumbo jets.

As serialization of unique parts becomes more popular as a method of tracking items from cradle to grave, manufacturers are turning more and more toward Direct Part Marking (DPM).

Serializing each component with DPM eliminates the human error factor, because with a quick decode workers know not only what product the part belongs to, but specifically where within the product (for example, a rubber sealing strip for a left rear car door). Area imagers are the technology of choice for all the various DPM manufacturing applications.

In light assembly applications, component manufacturers label parts with tiny 1D bar codes. Workers scan each serialized component when assembling the overall product for parts tracing, ensuring a customer order includes all requested features. Here the technology of choice is the laser scanner, for the ability to read small 1D bar codes, and for their motion tolerance for rapid picking and scanning of parts.

WAREHOUSE
Advanced data capture technologies have gone far in optimizing warehouse operations. Bar code scanning monitors product flow by collecting and transmitting information to a central database, which in turn provides visibility into the status of warehouse material.

At the receiving dock, employees unload packages and cartons and quickly scan their bar code labels to update package status. The item is then delivered to a staging area or directly to an outbound dock, where it is scanned again as it is loaded. This process enables real-time package tracking, allows delayed or missing items to be located immediately, and lets dispatchers predict when outbound trailer loading will complete. Laser scanners are suited to the warehouse floor, where motion sensitivity and long range scanning are issues as workers perform duties from forklifts. However, as traceability becomes more important in tracking packages and merchandise from cradle to grave, area imagers are necessary in decoding DPM or the 2D symbol that contains an item’s required historical data. Area imagers also allow workers to capture pictures of damaged packages for proof of sub-standard condition.

RETAIL
The retail industry was an early adopter of data capture technology throughout its multitude of applications. Because the amount and variety of retail merchandise is virtually limitless, automating processes is a must. Bar code technologies have helped accomplish this, from simplifying back-room inventory management to fostering speedy and more efficient checkout lanes.

In the back room, operators scan inventory to obtain a quick status of the quantity sold and on hand, so shelves can be restocked in a timely fashion. This significantly reduces the labor costs and errors associated with performing physical inventory, and, of course, yields greater customer satisfaction.

Here, laser scanners are the technology of choice, for their low cost and high performance in decoding UPC/EAN and other 1D bar codes used in retail. However, area imagers should be used if your situation requires capturing images for proof of condition, such as in delivery applications.

At the point of sale, checkout personnel use scanners to accomplish transactions accurately and efficiently with little training. The aim is to increase worker productivity and enhance the customer experience as checkout lines move swiftly and smoothly.

Omni-directional laser scanners can quickly scan bar coded items of all sizes and shapes, and cashiers can use cordless hand-held scanning devices to for heavy or bulky items right in the cart. Area imagers can take pictures of customers for ID membership cards. Hence, laser scanners are preferred for their motion tolerance in checkout, and area imagers should be used if the application requires image capture or decoding 2D bar codes. Laser scanners are the primary technology for portable shopping scenarios and price checker kiosks.

Based on information from Motorola (www.motorola.com), a supplier of both laser scannersand digital imagers.