In the early days of barcodes, codes could only be read by lasers. Laser scanners use a laser beam as a light source and typically employ oscillating mirrors or rotating prisms to scan the laser beam back and forth across the barcode. A photodiode then measures the reflected light from the barcode. An analog signal is created from the photodiode, and is then converted into a digital signal.
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Despite being an older technology, laser scanners still offer some operational benefits. Laser scanners do not require an image processor. They are also fast, capable of conducting up to 1,300 scans per second. Finally, because they use lasers – collimated beams of light that essentially do not diverge no matter how far the light travels from the source – they can read 1-D barcodes from relatively long distances with the use of special optics.
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This does not mean that laser scanners do not have limitations. Among their crucial limitations is that they cannot read 2-D codes, which are becoming increasingly more prevalent than 1-D codes. Laser scanners also can have trouble with 1-D barcodes that are poorly printed, low-contrast, distorted, or damaged. Because the environment for code reading is rarely perfect, the number of misreads and no-reads are typically too high. The combination of highly reflective parts and light sources often create hotspots that confound laser scanners.
Code position is also critical to laser scanners because, with few exceptions, 1-D codes must be scanned from left to right. This can require additional fixturing or mechanical systems to make sure an object's barcode is consistently oriented in a single direction. Laser scanners also have an oscillating mirror, and moving parts can break, resulting in additional costs and time required to repair or replace. Finally, due to eye safety concerns, laser scanners must be shielded to protect nearby workers.
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