Barcodes. Why do barcodes have the thick and thin lines and numbers on them. Also, why are lasers used to scan them?
In: 0
The numbers are for humans, the bars are for the laser. The laser sweeps across the bars and a sensor looks for reflected laser light. The white reflects a lot and the black very little, and this “on” and “off” is converted into 1’s and 0’s. This makes a series of longer and shorter pulses, depending on the angle at which the laser sweeps across the bars. Good scanners sweep at many angles, hoping to get lucky. The relative length of the string of bits is used, more like Morse Code than traditional computer numbers, to detect the coded numbers.
The size of the bars or the gaps between bars represent numbers which can be read by the light by converting the bars into a long number the item can be identified.
What you are describing sounds like an EAN barcode which is standard for identifying products in the global retail business. Each product gets a unique number so that the sales system can tally up the total, print a correct receipt, and keep track of how many remaining items is in the store.
The barcode is made to be easily read by machines even in low lighting, out of focus cameras, partially visible or if printed badly. To do this each digit is converted to two lines. The width of the lines and the space between them depend on the digit. The scanner will compare the width of the lines to decode the digit. The “laser” is used to illuminate the barcode and give the user a guide to where the scanning area is. The scanner uses a digital camera specially designed for this kind of work and software will identify the barcode.
The numbers that are printed is a failsafe. If the barcode is really bad then the scanner may not be able to read it at all. But a human are much better at reading the numbers then the scanner. So you can manually enter the number into the system. Next time you are at a self service checkout look for the manual barcode entry field.
Barcodes date back to when smart image recognition was beyond the capabilities of cheap personal/company computers.
The numbers written under the barcode are for us humans to read.
The bars themselves represent the numbers in an easily machine-readable form. Think of a barcode as being something like morse code – each pattern of black lines and spaces represents a particular number:
https://en.wikipedia.org/wiki/Universal_Product_Code#Encoding
A laser scanner is typically used for reading because it’s simple… instead of using an entire photographic sensor, the scanner just has to shoot a laser beam at the code and then use a single “photo diode” to read back whether it’s seeing light or dark at any particular moment and to decode those patterns of light and dark back to their corresponding numbers.
Okay, so what do those numbers mean? Well, that depends on context. Barcodes are used in a lot of places, not just in stores. They’re also used in warehouses and shipping hubs and manufacturing processes. For simplicity’s sake, I’ll stick to the “UPC” barcodes used at stores: Some of the numbers have some actual meaning like who is the manufacturer of the product, but most of them are pretty unique to the product. This means that every product has its own unique code, and you can build a database to track what each of those products is and how many of them you have on hand. E.g.,
|Barcode|Name|Price|Qty. In Stock|
|:-:|:–|–:|–:|
|482674972492|Spumco Baked Beans, 355mL|$0.99|24|
|673987147214|Pants On Fire Frozen Boneless Chicken Wings, 2lb|$3.99|8|
|337592657321|Deez Beer Nuts, 600g|$2.99|20|
It’s like words for computers. Basically the laser scans it and sends back where there is black and white. This is really easy for computers to read because white reflects the most light and black the least of the colors, to put it simply. Then it can tell where there is black and where there is white.
An easy way to think about it is each pixel of black adds one more to the count. So if it’s 7 pixels long, then that bar means a 7. But barcodes are much more complicated and it puts all these little numbers and indications it gets from it to decode a message. Basically a series of numbers that the computer then links up to a product in its system.
There are some barcodes like Coca Cola that pretty much every computer has the same because it’s on a list of universal barcodes. If you get chicken from the butcher at your grocery store, then it’s a barcode that’s only assigned to that in that grocery stores system
Latest Answers