Scanning and Barcodes

Codabar, Code 39, Code 93, Code 128, Industrial 2 of 5, Interleave 2 of 5, Matrix 2 of 5, MSI, Pharmacodes, Plessey, RSS14, Telepen, and UPC/EAN are a few of the standardized codes. Some of these are standardized under ISO. Others are not standardized within a particular industry. The symbologies vary by each standard. 1D, or linear codes, are read across, in a scanned line. Barcode symbologies use black bars and white spaces to encode a value. 2D, or matrix codes, are read as symbols in a matrix. CipherLab scanners and mobile computers read most of the standardized barcodes. For non-standard systems, our engineers will analyze your implementation to see what solution you need. For more information on a particular barcode symbology, there are many good sources on the Internet.

A scanner reads the code using light reflected from the code and a detector that senses the light and dark areas of the code. These physical characteristics are then processed into a code value, which is stored in data memory. If the reader is a scanner, the device it is attached to compares the value to a database and finds the item information. If the device is a mobile computer, it compares the value to data it contains in its own memory, or sends it to a server via a network. The information is processed based on the application the device is used for, such as checkout, warehouse inventory, etc. In summary, the code is scanned, interpreted into a value, then either transmitted to a computer for comparison to a database, or compared internally in the device. Finally, the data is processed by an application the data was originally intended for.

The scan engine is the part of a scanner or mobile computer that reads and interprets a barcode. When considering a scan engine, look at the following:
• Types of barcodes you'll be scanning, 1D or 2D
• Type of scanning technology, optical or laser
• Distance to the scanned object
• Physical environment
• Power consumption
• Ambient light and the size of the barcode

Laser scanning engines consume slightly less power than a CCD. For example, our 1166 BT Scanner (CCD) draws as much as 250 mA on full power, compared to the 1266 BT Scanner (laser), which draws only 15o mA on full power. Of course, other parts of the scanner draw power, and the lower power a battery operated scanner draws, the longer it will run between recharges.

1D, or linear scanning, scans a line across a barcode, such as a UPC or Code 39 code, detecting the reflected light differences of the bars. The barcode is simply a number or combination of letters and numbers that is an index to an item in a database; the barcode itself has no intelligence. 2D, or matrix, codes are arranged in a grid and can carry additional data, such as a description, manufacturer, date of birth, delivery address, etc. Intelligence is often built into the 2D code. The reader in the scanner is classified as a 1D or 2D reader that uses either an optical imager or a laser.

Performance. For short distances indoors, both technologies perform equally well. Outdoors the laser technology is a better choice, because of the laser's greater light intensity. For long distances, the laser is the only choice.

Function. Both technologies detect the reflected light intensity from the different characteristics of the target (barcode). Optical imager technology uses an LED (light emitting diode) to project light onto the target, while the laser uses a more intense laser beam. The scanning engine interprets the different reflected intensities as a code.

A laser is an intense, focused point of light. So, the laser scanning engine uses a rotating mirror to create a laser line that scans across the barcode. A detector in the scanner senses the changes in light intensity at the exact light frequency of the laser. This filters out other light sources that can cause misreads. The rotating mirror may require more frequent service or repair.

The optical imager scanning engine is constructed as an array of photo detectors (CCDs). An LED illuminates the code. A mirror inside the scanner gathers the reflected light from the code and projects it onto the CCD inside the scanner. With no moving parts, a CCD scanning engine requires little service.

Depth of field (DOF) specifies the closest to farthest distance a scanning engine can accurately read a code based on the size of the barcode. CipherLab laser scanning engines have greater DOF than the linear imaging engine. For example, our 1166 BT Scanner (CCD) has a DOF of 2 to 33 cm (0.8 to 13 in.), while the 1266 BT Scanner (laser) has a DOF of 1 to 63 cm (0.4 to 24.8 in.). Only laser scanners accurately read across longer distances. CipherLab offers both long range lasers (DOF 5 cm to 2.3 m/ 2 in. to 7.6 ft) and extra-long range lasers (DOF 15 cm to 13 m/16 in. to 43 ft.) in our mobile computers. Of course, the further the distance, the larger the barcode must be in order to accurately detect the code.

Resolution applies to optical imagers and indicates the density of the CCD array across its length. This determines the smallest barcode it can read. For example, the CipherLab 1100 Handheld Scanner uses a linear imager with 3648 pixels across its length, while the 1090+ Handheld Scanner imager has 2048 pixels. The 1100, with its denser linear imager can read smaller barcodes: 3 mil for the 1100 versus 4 mil for the 1090+.

The Print Contrast Signal value is a measure of reflectance of light between the black bars in a barcode and the white spaces between the bars. For a scanner, it indicates the minimum value required to accurately read barcodes. CipherLab scanners can accurately read a PCS of about 40 percent or better.

Ambient light can degrade a scan engine's ability to detect the reflected light from barcodes. This becomes more of a challenge with optical imagers, which are designed to detect the lower light levels of an LED, compared to laser scanners, which detect the more intense light of a laser. With optical imagers, sunlight essentially floods the light detectors.

These related characteristics determine how fast the scanner can capture accurate data. The scan rate depends on how fast the light can be detected by the laser or linear imager. The decode rate depends on how fast the scanner's computing technology can convert the detected light levels into information, such as an item number (from a 1D scanners) or the encoded information (from a 2D imager). Scan rate is typically specified with a particular decode rate in mind. read them.

PDA/Smart Phones/Mobile and ultra-mobile computers can scan barcodes if equipped with an image/barcode scanning engine and decoder tool. As demands for mobile use increase, we expect the scanning engine will soon be integrated into a single device, so workers have all the tools they need in their hands to get any job done.