BAR CODE READER

TABLE OF CONTENT

No Title Page

1 Introduction 3

2 Function of Barcode Scanner 4-7

3 How to read Barcode 7

4 Type of Barcode Scanner 8

5Comparison of Barcode Scanner reading

method 9

6 Application 9-10

7 Electrical wiring diagram of Barcode Scanner 11

8 Conclusion 12

9 References 12

10 Appendix 14

INTRODUCTION

What is barcode reader?

A barcode reader also called a price scanner or point-of-sale (POS ) scanner is a hand-held or stationary

input electronic device used to capture and read information contained in a bar code . Like a flatbed scanner,

it consists of a light source, a lens and a light sensor translating optical impulses into electrical ones.

A barcode reader consists of:-

a scanner ,

a decoder (either built-in or external), and

a cable used to connect the reader with a computer.

Nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the

sensor and sending the barcode's content to the scanner's output port. Whereby, a barcode reader will

captures and translates the barcode into numbers and/or letters, the data then is sent to a computer so that a

software application can make sense of the data. Barcode scanners can be connected to a computer through a

serial port , keyboard port , or an interface device called a wedge .

Figure 1: One of the Barcode Scanner Printer Magstripe PDA Integrated All in One 

FUNCTIONS OF BARCODE SCANNER

How do Barcode Scanners operate?

There are 3 functional parts to the barcode scanner itself,

the illumination system,

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the sensor / converter, and the decoder.

The simple way of barcode reader function

Barcode scanners begin by illuminating the code with red light. The sensor of the barcode scanner detects

the reflected light from the illumination system and generates an analog signal with varying voltage that

represent the intensity (or lack of intensity) of the reflection. The converter changes the analog signal to a

digital signal which is fed to the decoder. The decoder interprets the digital signal, does that math required to

confirm and validate that the barcode is decipherable, converts it into ASCII text, formats the text and sends

it to the computer the scanner is attached to.

Figure 2: How does a supermarket barcode scanner work

Each functional part of a barcode scanner in detail:

Illumination Systems - The illumination system is the method by which the bars and spaces on the barcode

are illuminated. There is a variety of illumination systems commonly used in barcode scanners:

Single Point LED - This technology is exclusive to the barcode pen reader and the barcode slot reader. The

illumination of the barcode comes from either a single or pair of LED's and is focused through a single ball-

type opening.  This technology requires the ball to physically touch the barcode being scanned.

 

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Figure 3: Barcode pen reader

 Since the illumination is on a single point, the operator has to provide motion to the barcode past the light

source. In the case of a barcode wand, the operator drags the illumination ball across the barcode. For swipe

or slot readers, the barcode is typically printed on a credit-card like media. The operator pulls the card

through a fixed slot, past the illuminating head. 

Slot and wand readers are inexpensive, and can accommodate any length of barcode. There are several

disadvantages of the single point illumination method. Slot and wand readers require the operator to control

the speed at which the barcode passes in front of the illumination head. Because barcodes must be in contact

with the illumination head to read, the barcode can easily be damaged by abrasion of the head on the media

that hosts the printed barcode. Although the illumination head is hardened, it will wear out and must be

replaced regularly.

Figure 4: CCD barcode scanner

Linear Multiple LED - Expanding on the single-point illumination system, placing multiple LED's in a line

give the ability to light the entire width of the barcode. This type of illumination is used in CCD scanners

and Linear Imagers.

When used in CCD scanners, the LED's are paired with a line of photocells to detect the reflected light from

the barcode Since the LED's are relatively low in power, and the photocells are low in sensitivity, the range

of CCD barcode scanners is generally limited from being in contact with the barcode to 1" away.

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Figure 5: Laser Image scan

Laser - This type of illumination method uses a single point red laser diode similar to a laser pointer. The

point of light is expanded into a line by oscillating the laser into a stationary mirror, or projecting the point

into an oscillating mirror.  This illumination method is very popular because of the working distances

typically achieved are superior to the point illumination or linear LED illumination methods. Typical

working distances are from 1" to 18". By increasing the power of the laser and decreasing the angle of

oscillation, ranges of over 20 feet can be obtained.

LED Imager - The linear and full imager is very similar to the CCD device, with some important changes.

In linear imagers, the amount of illumination is increased by using high light LED's, and the sensing

photocells are more sensitive. Linear imaging technology mimics both the range and focus of laser scanners.

In full imagers, high-intensity LED's illuminate a square scanning "target". The light sensors in full imagers

are very similar to the light sensors in monochrome cameras. The sensors search the scanning square target

for a valid barcode. By pairing the target square with sensors that search the target square for a valid

barcode, LED full imagers are receiving signal from directional - you don't have to line up the barcode in

any way in order for it to be decoded. The target / snapshot method give LED imagers the ability to read 2-

dimensional barcodes as well.

Regardless of the method used to illuminate the barcode, the illumination method is causes reflected light to

return to the scanner head and be seen by the sensor.

Figure 6: Light reflection from barcode scanner

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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.

The technology used in the sensor can vary depending on the illumination method. The output is always the

same - a voltage wave form with peaks for the white spaces, and troughs for the black spaces in the barcode.

In an imaging barcode scanner, the sensor covers the entire scan target and generates a 2-dimensional wave

form. In both cases, this analog signal is sent to the converter. The converter changes the analog signal to a

digital signal. This signal is the digital representation of what the sensor detected from the reflected light.

Now that the barcode scanner has a digital signal, the signal is transferred to the barcode scanner decoder .

HOW TO READ BARCODE

A bar code consists of white and black bars. Data retrieval is achieved when bar code scanners shine a light

at a bar code, capture the reflected light and replace the black and white bars with binary digital signals.

Reflections are strong in white areas and weak in black areas. A sensor receives reflections to obtain analog

waveforms. The analog signal is converted into a digital signal via an A/D converter. (Binarization) Data

retrieval is achieved when a code system is determined from the digital signal obtained. (Decoding process)

TYPE OF BARCODE READER

There are five basic kinds of barcode readers -- pen wands, slot scanners, Charge-Couple Device ( CCD )

scanners, image scanners, and laser scanners.

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A pen wand is the simplest barcode reader. It contains no moving parts

and is known for its durability and low cost. A pen wand can present a

challenge to the user, however, because 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 bar code at a certain speed

A laser scanner, either hand-held or stationary, does not have to be close

to the bar code in order to do its job. It uses a system of mirrors and lenses

to allow the scanner to read the bar code regardless of orientation, and can

easily read a bar code up to 24 inches away. To reduce the possibility of

errors, a laser scanning may perform up to 500 scans per second.

Specialized long-range laser scanners are capable of reading a bar code up

to 30 feet away

A slot scanner remains stationary and the item with the bar code on it is

pulled by hand through the slot. Slot scanners are typically used to scan

bar codes on identification cards.

A CCD scanner has 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. Each time the

bar code is scanned; several readings are taken to reduce the possibility of

errors. A disadvantage of the CCD scanner is that it cannot read a bar

code that is wider than its input face.

An image scanner, also called a camera reader, uses a small video

camera to capture an image of the bar code and then uses sophisticated

digital image processing techniques to decode the bar code. It can read a

bar code from about 3 to 9 inches away and generally costs less than a

laser scanner.

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COMPARISON OF BAR CODE SCANNER READING METHODS

Advanced scanning

CCD Laser Pen

Features Poor quality and remote label reading Fast reading Impact resistance

Fast reading Impact resistance

Remote and wide label reading

Inexpensive

Disadvantages - Does not read remote labels well

Low impact resistance

Practice required for operation Remote reading not possible

APPLICATION

I. Sales

Portable POS system Description:The Portable POS system can read a bar code for sales goods to display merchandise information such as the product name and sales price. Combined with a pocket printer, the system can also issue a receipt.

Advantages:The portable POS system allows speedy sales operation.As it is portable, POS can be realized in a vehicle, train or temporary shop.Sales performance data is processed at a host for sales analysis

Merchandise replenishment system Description:Have the merchandise replenishment system read the bar code for the merchandise to be replenished and enter an ordering quantity. Send the accumulated ordering data to the host to complete order placement.

Advantages:The merchandise replenishment system allows detailed merchandise inventory control.Merchandise can be accurately and quickly replenished.

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II. Logistics

Warehouse shipping/receiving control system

Description:The warehouse shipping/receiving control system can read bar codes attached to shipping/receiving products to perform checking on the spot.

Advantages:The warehouse shipping/receiving control system allows real time delivery status control.Delivery time can be accurately managed

Package tracking control system Description:The package tracking control system can read bar codes of package slips to control delivery status. Data from the delivery destination can even be sent via PHS data communication.

Advantages:The package tracking control system allows real time delivery status control.Delivery time can be accurately managed.

III. Manufacturing

Operation process control system Description:The operation process control system reads bar-coded worker numbers, part numbers, process numbers, etc. before and after operation.

Advantages:The operation process control system facilitates progress supervision, which leads to quality improvement.Operation hours per process can be analyzed to achieve optimal line allocation.

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ELECTRICAL WIRING OF BARCODE READER

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CONCLUSION

As a conclusion, we know that a barcode system is a network of hardware and software sensor that we can use for with using a lens and a light sensor translating optical impulses into electrical ones. By using these systems, it can make our life simpler regarding controlling the data that we have in our systems. We also have so many choices to choose what barcode system that we can use.

REFERENCESS

1. http://whatis.techtarget.com/definition/0,,sid9_gci857995,00.html >, Taken from What.com on Definition of Barcode Scanner. Access on 18 Oct 2010

2. http://www.carolinabarcode.com/how-barcode-scanners-work-a-69.html, Taken from Caroline barcode.com for How barcode scanner works. Access on 18 Oct 2010

3. http://en.wikipedia.org/wiki/Barcode_reader >, Taken from Wikipedia for barcode details. Access on 19 Oct 2010

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