About how bar code works.

1. BARCODE AND BARCODE SCANNER

2. Presented By
Name ID
Sarker, A.S.M. Imrul Hasan 13-24714-2
Hossain, MD Alamin 13-24757-2
Ahammod, Moeen Uddin 14-27450-2
Momen, Mahfuza 14-26494-2
Instructor : Rethwan Faiz

3. What is Barcode
 A machine-readable code in the form of numbers and a pattern of parallel lines of varying
widths, printed on a commodity and used especially for stock control.
 A barcode system is a network of hardware and software, consisting primarily of mobile
computers, printers, handheld scanners, infrastructure, and supporting software.

4. How Barcode Represent 0-9
Each digit in a barcode is represented by seven equal-sized vertical blocks. These are colored in either
black or white to represent the decimal numbers 0-9. Each block has been designed so that, even if
you turn it upside down, it can't be confused with any other.

5. BARCODES CAN BE QUITE LONG AND THAT'S BECAUSE
THEY HAVE TO REPRESENT THREE DIFFERENT TYPES OF
INFORMATION.
THE FIRST PART OF A BARCODE TELLS YOU THE COUNTRY
WHERE IT WAS ISSUED.
THE NEXT PART REVEALS THE MANUFACTURER OF THE
PRODUCT.
THE FINAL PART OF THE BARCODE IDENTIFIES THE PRODUCT
ITSELF. DIFFERENT TYPES OF THE SAME BASIC PRODUCT.

6. Sensor and Converter
 A photo detector senses the reflected light and generates an analog signal with
varying voltage. The voltage fluctuates based on whether the sensor sees the
reflected light from the white spaces because the black bars absorb the red
light.

7. Barcode scanners scan across a bar code and measure the intensity of the
reflected light. The light variation is converted into a digital signal.
A BARCODE SCANNER CONTAINS TWO BASIC SECTIONS. THE FIRST SECTION IS
A SCANNER THAT CONVERTS THE IMAGE INTO A DIGITAL REPRESENTATION.
THE SECOND SECTION IS A DECODER, WHICH COMBINES THE BINARY DIGITAL
SIGNALS INTO A SERIES OF CHARACTERS. THE DECODED INFORMATION IS SENT
TO THE COMPUTER VIA KEYBOARD OR SERIAL INTERFACE.

8. Input Device
 An input device accepts the reflected light and converts the
optical reflection into digital/analog signals.
 There are two major methods used for input; laser beam
and CCD (charge-coupled device). CCD scanners can be
very small, but they have less depth of field than laser
scanners.

9. Decoders
A decoder interprets the symbolic information and passes it to a host computer or
stores the information in memory. A decoder accepts the digital signal from the
input device and converts it to bars and spaces. Then it quantifies the element
width and decodes the signal.
Finally, it performs character checks. After the decoding process is complete, it
transmits the data to a host computer.
Decoders can be divided into two categories: on-line decoders and portable
decoders. The on-line decoder uses the power from an AC adapter or a computer
and the latter uses a battery.

10. Trimmers
Trimmers are located in the laser diode driver
and are used to bias and adjust the feedback of
the amplifier.

11. How does a barcode scanner work
 Scanning head shines LED or laser light onto barcode.
 Light reflects back off barcode into a light-detecting electronic component
called a photoelectric cell. White areas of the barcode reflect most light; black
areas reflect least.

12. As the scanner moves past the barcode, the cell generates a pattern of on-off pulses that
correspond to the black and white stripes. So for the code shown here ("black black black white
black white black black"), the cell would be "off off off on off on off off.”
An electronic circuit attached to the scanner converts these on-off pulses into binary digits
(zeros and ones).
The binary digits are sent to a computer attached to the scanner, which detects the code as
11101011.

16. The End
Thank You