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Why can't the barcode be scanned if the barcode scanning gun is too close to it?

Release Time:2020-07-29

If we can't accurately grasp the distance of the barcode scanning gun from the barcode, it is easy to "scan the barcode" or "need to scan several times to scan. At this time, I believe many users will doubt whether there is something wrong with the scanning gun, or blame it on the poor scanning performance of the scanning gun. In fact, this is a wrong understanding.

It involves a professional term for scanning guns, called the best working distance. The barcode scanner has an optimal working distance for the highest resolution performance, the so-called focal length. The resolution of the barcode scanning gun is adjusted according to the focal length, which can also be said to be the ability of the barcode scanning gun to decode the narrowest strip width. For this reason, if the distance between the barcode scanning gun and the barcode changes, the narrow bar and blank area of the barcode may not be read correctly, so there will be a phenomenon that the barcode scanning gun cannot scan the barcode.

Let's take a look at the differences between the red bar code scanning gun and the laser bar code scanning gun.

1) Red bar code scanning gun:

In the camera, the barcode image on the red image sensor is captured through the lens based on the red barcode scanning gun. Therefore, if the captured image is not in focus or the barcode is blurred, it will be difficult to identify the barcode.

2) Laser barcode scanning gun:

The spot diameter is smallest at the focal length. At positions larger or smaller than the focal length, the spot diameter becomes large, and the barcode/blank area cannot be recognized. The resolution is highest at the focal position. Therefore, the barcode scanner may also recognize uneven printing density, dust and scratches as part of the barcode. Therefore, when reading barcodes with low printing accuracy or fibers (such as cardboard) on the background, we need to pay attention to matching the focal length and narrow strip width.