Barcode scanner types
A barcode scanner (also referred to as a barcode reader) is an electronic device that reads printed barcodes. Like a flatbed scanner, it consists of a light source, a lens, and a light sensor that translates optical impulses into electrical ones. Additionally, nearly all barcode scanners contain decoder circuitry that analyzes the barcode's image data provided by the sensor and sends the barcode's content to the scanner's output port. There are three types of barcode scanners: 1 dimensional (1D) and 2 dimensional (2D) are the most common types of barcode readers; omni-directional scanners (the third type) are less prevalent.
- Laser (1D)
Laser type barcode readers/scanners consist of a light source (laser beam) and a photodiode that are placed next to each other in the read head and typically use either a reciprocating mirror or a rotating prism to scan the laser beam back and forth across the barcode. The photodiode is used to measure the intensity of the light reflected back from the barcode. The light emitted by the reader is tuned to a specific frequency and the photodiode is designed to detect only this modulated light of the same frequency. - Camera-based (2D)
2D imaging scanners are the newest type of barcode reader currently available. They use a small video camera to capture an image of a barcode. The reader then uses sophisticated digital image processing techniques to decode the barcode. Video cameras use the same CCD technology as in a CCD barcode reader except that instead of having a single row of sensors, a video camera has hundreds of rows of sensors arranged in a two dimensional array so that they can generate an image. This scanner also has no moving parts which tends to make them more robust and reliable. - Omni-directional
Omni-directional scanning uses series of straight or curved scanning lines of varying directions in the form of a starburst, a lissajous pattern, or other multi-angle arrangement are projected at the symbol and one or more of them will be able to cross all of the symbol's bars and spaces, regardless of the orientation. Almost all omni-directional scanners use a laser. Unlike the simpler single-line laser scanners, they produce a pattern of beams in varying orientations allowing them to read barcodes presented to them at different angles. Most omni-directional scanners use a single rotating polygonal mirror and an arrangement of several fixed mirrors to generate their complex scan patterns.
Housing types
- Handheld scanner - Has a handle and typically a trigger button to switch on the light source.
- Pen scanner (or wand scanner) - A pen-shaped scanner that is swiped.
- Stationary scanner - Wall- or table-mounted scanners that the barcode is passed under or beside.
- Fixed position scanner - An industrial barcode reader used in a fixed position such as conveyors and Product Flow Controllers (PFCs).
Resolution
Barcode scanner resolution is measured by the size of the dot of light emitted by the reader. If this dot of light is wider than any bar or space in the barcode, it will overlap two elements (two spaces or two bars) and may produce wrong output. On the other hand, if a too small dot of light is used, then it can misinterpret any spot on the barcode, making the final output wrong. The most commonly-used dimension is 13 mils (0.3302 mm). As it is a very high resolution, it is extremely important to have barcodes created with a high resolution graphic application.
Considerations and cost
Barcode scanner cost can range from several hundred dollars and up depending on the make, model, type, and features. Cost will always be a component of the scanner purchasing decision, but by no means should it be considered the determining factor.
Here are some important factors to consider besides cost when deciding to purchase a barcode scanner:
- How will the material be labeled?
- How will the PCB be labeled?
- Footprint required for barcode location?
- Will 1D suffice or must 2D be used?
- Laser-etched barcodes versus the more common printed label barcodes?
- Pen, handheld, or fixed mount scanners?
- Resolution requirements
- Are the barcodes able to withstand the environment to which the will be exposed (Baking, Reflow, Wave Solder, Water Wash)?
- Connection type
- Scanning distance, character length
- Ability to program a prefix and suffix
Barcode scanner technology and selection
The following tables outline some of the pros and cons related to 1D and 2D barcode scanners.
1D technology pros and cons
| Pros | Cons |
|---|---|
Far greater scanning/read distance than 2D | Requires a large footprint on the product being labeled |
Considerably cheaper scanner cost over 2D | Typically constrained to numeric or alphanumeric characters |
| Labels usually contain human readable content on the barcode 2D | Will not read/scan a 2D barcode |
| - | Scanners contain moving parts and tend to be less robust in handling |
| - | The smaller you make the footprint generates a less reliable scan |
2D technology pros and cons
| Pros | Cons |
|---|---|
| Small footprint | More expensive than 1D scanners |
| Can contain a vast amount of information | Not always compatible with 1D |
| Not limited to alphanumeric characters | Scanning distance is typically very short |
| No moving parts so tend to be more robust | - |
| Scanners can have a very tight scanning window | - |
| Better suited to laser-etched barcodes | - |
Scanner selection
A matrix of all available barcode scanners, manufacturers, and specifications is outside the scope of this guide. After you determine the symbology (1D or 2D) to use and the desired price point, we recommend you evaluate barcode scanners thoroughly before making your selection.