- It is an electronic device that can read and output printed barcode to a computer.
- In June 1974, one of the first UPC scanner, made by NCR Corp, was installed at Marsh's supermarket in Troy, Ohio. On June 26, 1974, the first product with a bar code was scanned at a check-out counter.
- It was a 10-pack of Wrigley's Juicy Fruit chewing gum.
Types:
- Pen Type Scanner:
- It contains no moving parts and is known for its durability and low cost.
- It has to remain in direct contact with the bar code, must be held at a certain angle and has to be moved over the barcode at a certain speed.
- Slot Scanner:
- It remains stationary and the item with the barcode on it is pulled by hand through the slot.
- Slot scanner are typically used to scan barcodes on identification cards.
- CCD Scanner:
- CCD scanner is a better read range than the pen wand and is often used in retail sales.
- Typically, a CCD scanner has a "gun" type interface and has to be held no more than one inch from the bar code.
- A disadvantage of CCD scanner is that it can't read a bar code that is wider than it is input face.
- Image Scanner:
- It is also called a camera reader, uses a small video camera to capture an image of barcode and then uses sophisticated digital image processing techniques to decode the bar code.
- It can read a barcode from about 3 to 9 inches away and cost is less compared to laser scanner.
- Laser Scanner:
- It is either hand-held or stationary, does not have to be close to the barcode in order to do its job.
- It uses a system of mirrors and lenses to allow the scanner to read the barcode regardless of orientation and can easily read a barcode upto 24 inches away.
- To reduce the possibility of errors, a laser scanning may perform up to 500 scans per second.
Working:
- Let's assume that barcodes are simple on-off, binary patterns with each black line corresponding to a one and each white line a zero.
- Scanning head shines LED or laser light onto barcode.
- Light reflect back off barcode into a light detecting electronic component called a photoelectric cell. White areas of the barcode reflect most light, black area reflect least.
- As the scanner moves past the barcode, the cell generates a pattern of on-off pulses that correspond to black and white stripes. SO for the code shown here, the cell would be "off off off on off on off off".
- An electronic circuit attached to the scanner converts these on-off pulse into binary digits.
- The binary digits are sent to a computer attached to the scanner which detect the code as 11101011.
- In reality sanners don't detect zeros and ones and produces binary number as their output, they detect sequences of black and white strips, but convert them directly into decimal numbers giving a decimal number as their output.
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