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This article discusses two types of competing and sometimes complementary devices - a laser barcode scanner and an imager scanner (a scanner that uses image scanning technology).

Recently, bar coding is increasingly entering various industries. As new barcode symbols appear every year, users have more and more choices for data collection. Bar code symbols can be called bar code languages.

Each symbology has its own method of reading the black and white stripes/spots of transmitting digital or alphanumeric information. Laser scanners and imagers perform the task of decoding this information. They can decode UPC/EAN symbols used in most grocery stores or ISBN symbols placed on books, as well as 2D 2D symbols, including PDF 417 or QR codes.

Laser Barcode Scanners or Digital Imagers

Laser Scanning Technology

How do laser scanners actually “read” a bar code? These scanners employ two optical systems to help with the task.

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 photo-detector. The collection optics also enable 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.

Advantages of laser technology

• 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 that require motion insensitivity, such as supermarkets, where users can rapidly swipe item after item over a fixed scanner. This motion tolerance also pays off in hand-held scanning, where the user can quickly and effortlessly move from one bar code to the next. In both situations, the laser scanner allows operators to achieve high productivity.

• Because laser scanners have been around for awhile, the technology has been refined to the point where many of these scanners are 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 2-dimensional bar codes. Because laser scanners can, however, read PDF417, a 2D-like symbology, they can also be a cost-effective option in PDF417 applications.

• Laser scanners can project a beam of light a long distance without diverging, or spreading out, as light from other sources do, enabling them to decode high density bar codes over wide ranges. This proves advantageous in applications that require scanning range flexibility, such as forklift operations where packages are often located on high shelves or hard-to-reach areas. In these cases, laser scanners can achieve 50% more range than more expensive area imagers.

• Because the laser is emitted from the line of sight of the scanner’s sensor, accurate scanning is easy. 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 Imaging Technology

Digital image scanning technology uses a different approach to scanning, but with the same goal of efficiently reading barcodes. There are two types of image reading technology.

Area Imagers

Digital area imagers use a different approach to decoding bar codes, but with the same end result in mind – to quickly and efficiently read the bar code. The area imager projects LED light that illuminates the target bar code. 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. Digital area imagers present many benefits when used 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 re-orient 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. This eliminates the need for additional equipment, such as flatbed scanners, saving counter space and reducing capital and maintenance expenses. This is also useful for proof of delivery, and in field service and shipping and receiving applications for recording images of damaged cartons for proof-of-condition claims.

• 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. The growing popularity of DPM has enabled serialization for unique parts to ensure product quality, and improved tracking efficiency in areas such as the pharmaceutical market to help achieve compliance with traceability regulations.

Linear Imagers

Linear imagers capture bar code data in a similar way as area imagers. Linear imagers project LED light onto a bar code, and a lens focuses the bar code image onto a CCD or CMOS sensor. A decoding algorithm analyzes the peaks and valleys of the signal and collects the bar code’s data. However, unlike area imagers, linear imagers use their sensors to capture only a single row of pixels within the image. This allows linear imagers to decode a 1D bar code, but not entire images or 2D bar codes as an area imager can. And because economical laser scanners facilitate intuitive aiming, have better motion tolerance, and are typically as reliable and rugged, they are a better choice than linear imagers for almost all 1D scanning applications.

Common Misconceptions

Regarding Bar Code Decoding Technologies

Misconceptions often arise when attempting to select the best technology to simplify and increase efficiency in business applications and lower operational overhead. We’ll address a few of these misunderstandings now.

Misconception #1:

Digital Imaging and Laser Scanning – One Technology is More Reliable Than the Other

When it comes to data capture technology, manufacturers of digital imagers or laser scanners typically promote their technology as being more reliable. Rather than generalize the superior reliability of one, customers must carefully analyze their individual data capture situation and then determine which method best suits their needs. Today’s high-performance laser scanners use frictionless elements that enable them to ship with a lifetime warranty because of their dependability. Digital imagers, on the other hand, also boast outstanding reliability based on their solid-state construction due to a lack of moving parts. In retail establishments, you’ll often see digital imagers or laser scanners that are 10 to 15 years old operating as efficiently as ever.

So when choosing a data capture technology, be sure to apply thoughtful analysis to both the present and future needs of your enterprise, and consult the experts. This planning will pay off in application efficiency and worker productivity.

Misconception #2:

Linear Devices Support Imaging

While linear devices such as CCDs (Charged Coupled Devices) are often called “linear imagers”, this misnomer fosters the mistaken idea that such devices are capable of imaging. Linear devices use CCD or CMOS sensors to process bar code information in the same manner as area imagers. However, linear imagers use the sensors to capture a thin slice of an image (i.e., a single row of pixels), while area imagers use sensors with pixels arranged in a 2-dimensional grid (multiple rows). While this allows linear imagers to decode a 1D bar code, it does not result in a useful image for anything else.

Misconception #3:

MEMS Scanners Outperform Other

Laser Scanners

Micro-electromechanical system (MEMS) based scanners are often incorrectly understood to yield performance superior to other laser scanners, based on the replacement of a single design element, the scanning mechanism. This new element enabled a frictionless scanning system. And although we know frictionless means more reliable, there had already been other types of frictionless scanners on the market for years. However, it is also important to understand that in a complex laser scanner system, there are several things that affect performance. Merely replacing the scanning mechanism to increase scan speed will not provide the superior scanning ability many users expect. In reality, increasing the scan speed reduces signal quality, which often results in decreased working range and poor performance in decoding degraded bar codes, offsetting the benefit of the increased speed. Sensitivity to bright ambient light conditions further degrades signal quality for MEMS scanners. To balance out these negative consequences and achieve its desired working range, a MEMS scan engine must increase the size of its optics, resulting in a much larger engine. Engine size plays a key role in scanning device ergonomics, where a smaller engine efficiently allows an optimized housing design. MEMS engines fall short in this area. A well-designed, high-performance scanner, such as those based on Symbol’s LP engines, uses the appropriate technology and thoughtfully integrates system components in a way that maximizes scanning range and performance on both high quality and damaged bar codes.

Data Capture Markets

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 can profit by using either or both.

Conclusion

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