Barcode scanning: short range vs. long range

The job of a bar code reader is comparatively simple: to detect the characteristics of the white space between the dark bars. Bar code readers shine a light (usually a red light or red laser light) onto a bar code and detect the light reflected back. There are a number of bar code reader technologies with different levels of resolution and sensitivities at various distances.

Most bar code readers are not cameras but use a lens and a light sensor (although some are actually cameras). Most of the time, bar code readers sense only light and dark. They need motion to enable them to sense an entire bar code. The motion can be supplied by a hand movement, by a movement of the sensor, or by the movement of a subject passing in front of the sensor driven by a conveyor.

Short-range vs long-range barcode scanning

The wand or pen scanner was the first kind of hand-held scanner. The wand was moved across the bar code to generate a dark on or off sequence. Illumination came from one or two red light-emitting-diodes (LEDs) that had to be held in contact with the barcode. 

Modern short-range bar code readers are usually hand-held devices that can read bar codes within a few inches from the scanner. These may be illuminated by rows of low powered LEDs paired with CCD light sensors. The scanner heads move across the code returning a dark on or off pattern signal which is software translated into the alpha-numeric reading. 

Long-range scanners may use a single red laser as a light source. The light from the laser is expanded into a line-pattern using an oscillating mirror so that an entire bar code can be covered. The light source may also be a row of high intensity LEDs. Typical LED or low-powered laser scanners can read bar codes at about 18 inches distant. Increase the power of the laser and the reader may be sensitive at ranges in the 20 foot range.

Some long range scanners, called "full imagers" use high intensity LED lights with camera-like light sensors that can make a "snapshot" of the bar code. These can read more complex two-dimensional bar codes as well as one-dimensional bar codes. 

Supply Chain Services is an award winning provider of barcode data collection solutions.  Please contact us to determine which barcode scanner is right for your operations.

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