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Barcode Scanner


WHAT IS BARCODE SCANNER?

Many different types of bar code scanning machines exist, but they all work on the same fundamental principles. They all use the intensity of light reflected from a series of black and white stripes to tell a computer what code it is seeing. White stripes reflect light very well, while black stripes reflect hardly any light at all.


MANUFACTURING PROCESS

Hologram disk:

The first step in the manufacturing process is to mass produce the hologram disk. This disk is replicated from a master hologram. All the disks, master and reproductions, are sandwiches made of plastic "bread" with DCG filling. Master disks are made in sections, one wedge for each different reflection angle required in the final disk. A typical point-of-sale scanner will have between 7 and 16 wedges on a single disk. Holographic recording is done with two laser beams that intersect at the surface of the DCG sandwich, creating the holographic pattern. Adjusting the angle at which the two beams meet will change the reflective properties of each hologram. Each wedge created in this way will act like a mirror that is turned in a different direction. Once all the required wedges have been recorded, they are assembled and glued down on a single transparent plate, which can then be replicated. The glue used has optical properties that will not distort the hologram image, such as glycerin-based adhesives will. There are many ways to replicate a hologram, but the most common for DCG holograms is optical replication. The master disk is placed close to, but not touching, a blank DCG sandwich disk, and a single laser beam is used to illuminate the master from behind. This transfers the pattern onto the blank.

Lenses, mirrors, laser:

Other components—lenses, mirrors, laser, etc.—are usually purchased from an outside manufacturer. Lens, mirror and scan window properties are specified during the design process. The manufacturer tests all of these components as they arrive to confirm that they meet specification. Motors and lasers are tested for proper operation, and some are lifetime tested to make sure that the bar code scanner will not fail within a reasonable period of time.

Housing:

Housing can be purchased from a metal job shop, or it can be fabricated by the manufacturer. The size and exact shape of the box is specified in design, and manufacturing converts those specifications into realizable sketches.

Final assembly:

Finally, the hologram disk is assembled with the spinning motor drive and tested. Scanning pattern, direction, and speed are all examined. The spinning disk is then assembled with the optical system (the laser and mirrors). Placement of the laser often depends on space considerations: the laser can be aimed directly at the spinning disk, or at a mirror that guides the beam to the disk, if this makes the package smaller. The disk and optical system are tested as a unit. When the assembly passes inspection, it is mounted permanently inside the housing and sealed with the scanning window.

Quality Control:

There are several stages to quality control in bar code scanner manufacturing. To begin with, there are several test criteria that are defined within the bar code industry and that must be specified by all manufacturers. These include:

  • First Pass Read Rate (FPRR)—the percentage of time that a code can be read the first time it passes the scan window

  • Rejection Rate—the number of scans per million which simply won't be read

  • Read Velocity—the range of speeds with which a code may be passed over the surface of a scanner

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DISCLAIMER The information is provided by Tecquisition for general informational and educational purposes only and is not a substitute for professional legal advice. If you have any feedback, comments, requests for technical support or other inquiries, please mail us by tecqusition@gmail.com.


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