Bernard Silver, a graduate student use this code but silver failed a patent application .
The first attempted at an industrial application of automatic identification was begun in the late 1950's by the Association of American Railroad.
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.
The barcode standard adopted by the automotive industry ,the Department of defence.
COMPARE WITH OLD TECHNOLOGYErrors occur in both data collection and keyboard entry of the data when it is accomplished .The average error rate of manual keyboard entry is error per 300 characters.
Time factor. Manual methods are inherently more time consuming than automated methods.There is a time delay between when the activities and events occur and when the data on status are entered into the computer .
Labor cost.The full attention of the human workers is required in manual data collection and entry ,with the associated labour cost.
A barcode is an optical machine-readable representation of data relating to the object to which it is attached.
Originally barcodes systematically represented data by
varying the widths and spacing of parallel lines.
The barcodes give the numerical values or variables.
Barcodes can be two types .
1. One dimensional or linear barcode.(fig.
2. Two dimension barcode. (fig. b)
Types of barcodes:
Linear barcodes are mostly used automatic identification and data collection technique .
The 1 -D barcodes are in two forms :
a) Width -modulated b) Height -modulated
different kind of 1-D barcode
a) Height-modulatedIn this kind of barcode the symbol consists of evenly spaced
bars of varying height.
The only significant application of this kind is in the U.S. Postal Services for ZIP code identification.
Here the symbol consists of a sequence of wide narrow coloured bars separated by wide and narrow spaces.
The colour bars are usually black and the spaces are white for high contrast.
The pattern of bars and spaces is coded to represent the numeric or alphanumeric characters.
Mechanism The barcode reader has a light source like Laser and a
Photodiode on the head. The light source emits light which reflects back from the
space between the bar codes. The Photodiode measures the intensity of the reflected back
light when the head crosses each bar and the space between the bars.
The Photodiode generates a waveform corresponding to the width of the bars and spaces in the label. The light passes across the barcode label, the dark bands absorb light while the white spaces reflect light.
So the voltage waveform generating will be similar to the bar and space patterns.
The decoder translates the waveform into corresponding data.
Data collection process of 1-D bar code in the form of electric signals
Scanning of the 1-D data
fig. shows the different symbol and their significance example shows letter ‘i’
BARCODE READERS:Bar code readers come in a verity of configurations, some require a human to operate them and others are stand alone automatic units.
They are usually classified a Contact or Non contact readers.
The wand tip must be in contact with the barcode or very close proximity during the leading procedure .
This kind of readers are fixed in any position .
Contact barcode reader:
This kind are hand held wands or light pens operated by moving the tip of the wand quickly past the bar code on the object.
Non contact bar code readers:This kind of readers focus a light beam on the bar code and a photo detector reads the reflected signal to interpret the code.
The reader probe is located a certain distance from the bar code during the read procedure.
Non contact readers are classified as fixed(use fixed beam) and moving beam scanners(use highly focused laser beam .
2-D bar codes The first 2-d barcode was introduced in 1987.
Two-dimensional (2D) barcodes look like squares or rectangles that contain many small, individual dots.
A single 2D barcode can hold a significant amount of information and may remain legible even when printed at a small size or etched onto a product.
The area is reduced in compare to the one dimensional barcode.
Types of 2-D barcodes:2-D Barcodes
stacked bar codes matrix symbolise
Different kinds of 2-D barcodes:
a) Stacked 2-D bar code:
First two dimensional bar code was a stacked bar code.
It was developed in an effort to reduce the area required for a conventional bar code .
A stacked bar code consist of multiple rows of conventional linear bar code stacked on top of each other.
The data density of the stacked barcode is 5 to 7 times that of the linear bar code.
The encoded data in a stacked bar code are decoded using laser type scanners that reads the lines sequentially. EX:PDF417
b):Matrix symbologies:This was introduced around 1990.
It consist of 2-d patterns of data cells that are usually square and are coloured dark (usually black) or white.
Their advantage over stacked bar codes is their capability to contain more data .
This symbologies contain data 30 times to the linear barcode.Example:ECC200
Scanning of the 2-D barcode:
Drawbacks of the 2 -d barcodes:
Keeping track of the different rows during scanning .
Printing defects are possible.
Matrix symbology is more complicated .
For reading the data of the code require a sophisticated
machine vision system specially programmed machine.
Reduced Labor Costs.
A barcode reader can process barcodes from anywhere in the
Keyboard data entry creates an average of one error in 300 keystrokes. Barcode data entry has an error rate of about 1 in 3 million.
Fast and Reliable Data Collection.
Take small area.
Advantages of the barcodes:
Disadvantages of barcodes:If a barcode is ripped or damaged there is no way to scan the product.
Only readable .
Stores less data.
Can only be read individually.
In laser scanning durability and cost are two disadvantages.