FTA (изд-во). Flexography: Principles And Practices. Vol.1-6

Подождите немного. Документ загружается.

56 FLEXOGRAPHY: PRINCIPLES & PRACTICES

The EAN/UPC symbol

family of bar codes.

A Quick Course on

Common Bar Code

Symbologies

ccording to AIM International,

Inc., the worldwide trade asso-

ciation for the automatic iden-

tification and data capture

industry (see Resources),

there are approximately 225

bar code symbologies that have been pub-

lished around the world. However, only a

small fraction of these are being used in any

significant way, and fewer still have the wide-

spread acceptance of the familiar EAN/UPC

“product code” symbology.

Considered by many to be the genesis of

the modern bar code era, the EAN/UPC sym-

bol was formally introduced as a 12-digit

code in the United States by the Uniform

Code Council, Inc. (UCC) in 1973. In 1977,

the European Article Number Association

(EAN) adopted the U.P.C. product identifica-

tion system. The 12-digit code was expanded

to a 13-digit data structure to allow for its use

internationally. Today, the UCC and EAN

International manage the product identifica-

tion system together. There are over 820,000

member companies in 90 countries using

UCC/EAN identification numbering rules and

bar codes on countless products worldwide.

In fact, it is estimated that the EAN/UPC sym-

bology alone is involved in more than 5 bil-

lion product transactions a day on a global

scale. The numbering rules and bar code

specifications for the primary business appli-

cations (product identification, shipment

identification and coupon structures) en-

countered in the North American supply

chain are described today in a UCC docu-

ment called “Guidelines for Supply Chain

Identification’. Figure

shows the EAN/

UPC symbol family.

UPC-A

UPC-E

EAN-8

EAN-13

BAR CODES 57

A typical Code 3-of-9

(Code 39) symbol.

This system uses a

proportionally large

amount of space to

convey its information.

The EAN/UPC symbol belongs to the linear

family of symbologies, meaning it encodes its

data in a simple arrangement of bars and

spaces on a horizontal axis. Linear symbols

can then be scanned directionally and decod-

ed. This differs from the more advanced two-

dimensional bar codes which stack informa-

tion in multiple rows or in a matrix pattern

with both horizontal and vertical axes con-

tributing significant meaning. This type of

symbol requires more advanced scanning

techniques, but also delivers a large increase

in the capacity of information it is able to

encode.

The EAN/UPC is also considered to be a

continuous bar code symbology. Continuous

symbologies encode symbol characters with-

out any inter-character space between them.

In other words, as one symbol character

ends with a space, the next begins with a bar.

Compare this to discrete bar code symbolo-

gies, which treat each character indepen-

dently, separating them with loosely toler-

anced spaces (Table 11).

As manufacturers, distributors and other

supply chain members sought to identify

product configurations, shipments, compa-

ny assets, physical locations and product

attributes, new symbologies were intro-

duced. It is impossible to cover all the events

between the advent of EAN/UPC and today

regarding symbology development, but a

review of the major milestones can be cov-

ered fairly quickly.

In the late 1970s, the Committee to the

Department of Defense and the General

Services Administration recommended

Code 39 (also known as Code 3-of-9) for gen-

eral use (Figure

). Many commercial and

industrial businesses also picked up the

symbology for their applications. Named for

its distinctive encoding structure, Code 39

always features nine elements (five bars and

four spaces) with three of the nine elements

always being wide for each character encod-

ed. The symbology features a full alphanu-

meric character set and the ability to be vari-

able in length as required. It does, however,

use a significant amount of label space, mak-

ing it less desirable in certain applications.

Another popular symbology introduced in

the 1970s is ITF (Interleaved 2-of-5). ITF

(Figure

) is commonly encountered as

Table 11

ENDOCATION LENGTH

SYMBOLOGY TYPE DATA CONTENT METHOD ENCODING RESTRICTION

■ EAN/UPC FAMILY Numeric only Complex Continuous Fixed

■ CODE 39 (Code 3-of-9) Alpha-numeric Simple Discrete Variable

■ ITF (Interleaved) Numeric only Simple Continuous Fixed

■ Code 128 Alpha-numeric Complex Continuous Variable

CHARACTERISTICS OF SOME COMMON BAR CODES

58 FLEXOGRAPHY: PRINCIPLES & PRACTICES

the bar code specified for UCC/EAN prod-

ucts when they are packaged above the unit

level in corrugated cases (see ANSI/UCC6 –

Application Standard for Shipping

Container Codes). It is also used widely by

the airlines industry. As with Code 39, ITF

received its name from the way it encodes

its numeric-only character set. Each symbol

character contains five data elements (bars

or spaces), two of which are wide (2-of-5).

The “interleaved” reference comes from the

way the symbology takes digit pairs and

interleaves them into its symbol characters,

one in the bars and one in the spaces. This

simple structure dictates that an even num-

ber of characters must always be encoded.

Code 128 was developed in 1981, and its

name encompasses one of its primary assets

– the ability to encode the full 128-character

ASCII set (Figure

). Code 128 offers a

number of robust features that provide its

users with many options. It can encode vari-

able-length data and permits numeric data to

be encoded as two digits per symbol charac-

ter. This “double density” mode makes it one

of the most efficient symbols in widespread

use from the standpoint of the area it

requires for encoding numeric data. Code

128 is widely used by a host of industries

including healthcare, retail, food and grocery,

and transportation.

The UCC, in conjunction with EAN Inter-

national, licensed a unique subset of Code

128, called UCC/EAN-128, for the exclusive

use of encoding UCC/EAN-defined data. The

subset can be reserved because Code 128

encodes four special symbol characters

referred to as function characters (FNC1,

FNC2, FNC3 and FNC4). The UCC/EAN-128

symbology has a special double-character

start pattern consisting of either a start code

A, B, or C character as the first symbol char-

acter, and an FNC1 as the second symbol

character as shown in (Figure

). This

unique start code pattern tells the scanning

and decoding system that a UCC/EAN-128

has been scanned and the data should be

processed according to the UCC/EAN-128

“data dictionary” defined by UCC/EAN.

The ITF system codes

characters in sets of five

spaces and bars, thus

the moniker “2-of-5”

symbol.

By encoding two digits

per symbol character,

Code 128 is able to

communicate its data in

a relatively small space.

The UCC/EAN-128

symbology with a

special double character

start pattern consisting

of either a start code

A, B, or C character

as the first symbol

character, and an FNC1

as the second symbol

character.

The “8” in five bars

Start

Character

Stop

Character

The “3” in five spaces

(01) 3 00 12345 67890 6

FNC1

Start

Code C

(01) 3 00 12345 67890 6

Note: Some of the bars in Figure

are

shown in different colors for illustration

purposes only. Multiple colors or red colors

should NEVER be used in a UCC/EAN sym-

bol intended for actual use.

The UCC/EAN-128 “data dictionary” (for-

mally called ANSI/UCC4-UCC/EAN-128

Application Identifier Standard) is based on

using a series of two, three or four digit pre-

fixes in front of the actual data to be encod-

ed. These prefixes are called Application

Identifiers, or AI for short. For example, the

UCC/EAN specifies that the 14-digit product

identification number called UCC/EAN-14

(or SCC-14) has the AI prefix of 01 in front of

it to tell the scanning and decoding system

that the UCC/EAN-14 follows. This is very

much like the area code assigned to a tele-

phone exchange. Application Identifiers are

even put into parenthesis, like an area code,

when printed in the human readable text

associated with the UCC/EAN-128 symbol.

There are about 100 AI definitions and each

describe what type of data is encoded, how

long the data content is (fixed or variable

length fields), and what kind of data it can

contain (numeric versus alphanumeric). By

using AI prefixes, multiple identification

numbers can be concatenated (combined)

into one UCC/EAN-128 symbol. The scan-

ner/decoder system uses the AIs to deter-

mine the meaning and length of the data

behind each AI (by following the AI defini-

tions). Then the decoder strips the AIs out of

the data before it is sent to the business

application software. There is another

method of defining data called Data Identi-

fiers (DI) which is often used within Code 39

bar codes.

BAR CODES 59

60 FLEXOGRAPHY: PRINCIPLES & PRACTICES

he EAN/UPC and other symbol-

ogies are each considered to be

their own unique language, with

their own individual rules for

character encoding, decoding,

checking and other features.

But there are common features across the

spectrum of many bar code symbols that

illustrate a fundamental structure.

In their most common form, linear bar

codes are a series of alternating dark bars and

light bars (called spaces), in various widths,

which reflect light within an acceptable

reflectance tolerance as prescribed by specifi-

cations. Most linear symbols are bidirectional.

That means the symbol may be scanned left-

to-right or right-to-left with the same results.

EAN/UPC symbols are unique in that they can

also be scanned omni-directionally.

When scanned by an omni-directional

scanner, the EAN/UPC symbol can be read

by the reader at any orientation in which its

bars are presented to the scanner’s pattern

of scanning beams. The symbol design

requires that the height of the bars be some-

what greater than the width of any decod-

able segment of a symbol. This “over-square”

geometry guarantees that a scanner’s beams

will intersect all the required bars and

spaces to decode a symbol on a single pass

across the scanner. EAN/UPC symbols con-

sist of one or two decodable segments,

depending on the version. The most com-

mon versions of the EAN/UPC symbols con-

sist of two decodable segments that are

read as a single symbol. This symbol design

feature, when combined with special scan-

ning patterns used in checkout scanners,

speeds the checkout process in high volume

applications.

The key measurement in bar code symbol-

ogy is called the “X” dimension. Quite sim-

ply, X is the width of the narrowest bar or

space element in the symbol, and it sets the

parameters for the corresponding bar

widths, symbol length and sometimes height

of the printed bar code. Bar code application

standards (standard based on where the bar

code will be used) typically specify an

acceptable range for the X-dimension and

may also specify a nominal (or target) value.

The range specified correlates to the scan-

ners typically used in the application and the

type of scanning conditions that are encoun-

tered. For instance, some scanners scan very

small X-dimensions and require the symbol

to be in near-contact with the scanner, while

other scanners can scan symbols with large

X-dimensions from across a room. Some

scanners are operated by humans who can

find the symbol and adjust scanning

angle/distance while other scanners are

mounted to a conveyor and expect to see

symbols in a predictable location with a pre-

dictable X-dimension.

Another factor to consider for “two-width

symbologies” (symbols with only two ele-

ment widths

) is bar-width ratio. Bar-width

ratio is the relationship of wide-to-narrow

Symbol Structure,

an Overview

ITF and Code 39 are two width symbols. EAN/UPC, UCC/EAN-128 and Code

128 are not.

BAR CODES 61

Quiet Zones are print-

free areas that help the

scanner locate the bar

code symbol.

Guard bars (the twin

narrow lines shown in

red), divide the bar

code into left and right

segments.

elements, such as 3:1 or 2:1, where 1 is the X-

dimension (narrow element width). For two

width symbologies, the width of the wide ele-

ment grows in a fixed proportion to the size

set for the X-dimension (narrow element

width). The application standard (based on

where the bar code will be used) must take

the X-dimension and the bar width ratio into

account for two-width symbols. The bar-

width ratio may be specified as a nominal

value accompanied by an allowable range.

For instance, when the ITF symbol is speci-

fied by the UCC for use on shipping contain-

ers, it has a nominal bar width ratio of 2.5:1

and an allowable range of 2.25:1 to 3:1. These

application specifications for the minimum

X-dimension and bar-width ratio provide the

bar code designer and printer with the range

of bar code sizes that must be used.

Quiet zones are another common element

shared by most bar code symbologies

(Figure

). Quiet zones are print-free

zones, frequently measuring 9 or 10 times the

X dimension, that are used to separate the

bars and spaces from any surrounding graph-

ics or text. They are used to help the scanner

locate the symbol. These zones normally pre-

cede and follow start and stop patterns that

enable the scanner to decode the symbol.

These bar and space patterns, which are

unique to each symbology, identify the begin-

ning and end of a decodable segment of the

symbol, as well as the direction of reading.

In the EAN/UPC symbology, the start and

stop patterns are referred to as guard bars.

For UPC-A, EAN-13, and EAN-8 versions of

the EAN/UPC symbol family, the guard bars

are formed by twin narrow elements at the

beginning, center, and end of the symbol as

shown in (Figure

). They divide the sym-

bol into left and right decodable segments

that are then combined by the scanner into a

single symbol. For the UPC-E version of the

EAN/UPC symbol family, the guard bars are

formed by twin narrow elements only at the

beginning and end of the symbol and create

only one decodable segment. More details

can be found at the UCC web site in the doc-

ument ANSI/UCC5 – Quality Specification

for the U.P.C. Printed Symbol.

Note: Some of the bars in Figure

are

shown in different colors for illustration

purposes only. Multiple colors or red colors

should never be used in a UCC/EAN symbol

intended for actual use.

Beneath the black and white lines, many

bar codes maintain an acknowledgement to

those of us who are not machines. The

“human-readable text” as it is often called,

contains text characters that, when entered

manually into a system, can also unlock the

same encoded data referenced in the symbol.

The symbology specifications or application

standards set out how many text characters

Quiet Zones

62 FLEXOGRAPHY: PRINCIPLES & PRACTICES

are associated with the encoded data, the

spacing between text characters, and even

where the text should be located. There are

often text characters that are not encoded in

the bars and spaces, such as the parenthesis

around UCC/EAN Application Identifiers.

There are also symbol characters that may

not be included in the human-readable text,

such as symbol start/stop patterns and inter-

nal symbology check characters (module 103

for Code 128 and UCC/EAN-128).

Another major feature shared among most

bar codes is a method of error checking built

into the code. There are actually two ways a

bar code data carrier may be checked. The

first method, called self-checking or parity

checking, uses the graphic design of the

symbology itself to verify if a character is

encoded properly. One example of this

would be a symbology which requires that

there be an odd number of narrow bars in

every properly-encoded character; another

example would be a symbology which must

always have an even number of dark mod-

ules for each character. These symbol-

checking arrangements are joined by a sec-

ond method of checking called check digits.

Based on algorithms, check digits are calcu-

lated based on strings of numbers encoded

within the symbol, then the check digit is

encoded as part of the symbol as well. When

scanned, they allow the code inside the sym-

bol to be verified as a valid combination of

characters. This adds greatly to the high con-

fidence factor enjoyed by bar code users.

A final feature that is found on bar codes

such as the ITF symbol is bearer bars. The

UCC specifies bearer bars surround the ITF

symbol to reduce the probability of misreads

when the scanning beam is skewed in rela-

tion to the symbol. The bearer bars also pro-

vide printing plate support when the symbol

is printed directly on packaging materials

such as corrugated. When the symbol is

printed directly on the packaging material,

the UCC specifies the bearer bar completely

surround the symbol as shown in Figure

A bearer bar (the bar

encasing the bar code

symbol) reduces the

probability of scanner

error.

3 0 0 1 3 4 5 6 7 8 9 0 6

BAR CODES 63

Bar Code Design

Considerations and

Flexographic Printing

reparation for bar code design

and production begins with the

selection of the proper symbol.

Each symbology is clearly identi-

fied with its own applications.

The bar code used depends on

where and how the code it carries will be

scanned. Scanners used at the retail POS

(point of sale) checkout counter often differ

dramatically from scanners used in large dis-

tribution centers. There are even significant

differences among family members within the

same symbology. For instance, EAN symbols

used outside North America cannot yet be

scanned at many retail locations in North

America, but UPC symbols used in North

America can be read anywhere in the world.

Symbologies, including the EAN/UPC, ITF,

Code 39, and Code 128 are specified by sym-

bology specifications. The symbology specifi-

cations for all major symbologies (other than

EAN/UPC) are available from AIMUSA

. The

EAN/UPC specifications are available from

UCC

(ANSI/UCC5 – Quality Specification

for the UPC Printed Symbol). Beyond the

raw specifications for the bar and space

dimensions and encodation patterns, stan-

dards bodies closely regulate application

standards that govern where and how bar

codes are used to meet a business require-

ment. These application standards may even

specify a symbology subset such as

UCC/EAN-128 (ANSI/UCC4 – UCC/EAN-128

Application Identifier Standard). Designers

and printers should obtain the symbology

specifications and application standards gov-

erning the bar codes they create directly from

the source. The printer’s customer may also

be required to apply for a part of the identifi-

cation number itself. For example, the

Uniform Code Council and EAN Inter-nation-

al are the two coequal standards bodies which

oversee the global UCC/EAN system. Anyone

wishing to employ any symbols in this world-

wide network must first receive a company

prefix by making application to the UCC, the

EAN or one of their 90 affiliated numbering

organizations worldwide. The UCC publishes

a collection of symbology specifications and

application standards within the Art of

Producing Bar Codes Tool Kit for UCC mem-

bers and their suppliers. The Tool Kit naviga-

tion system is based on the UCC/EAN flagship

document for the design, preparation and pro-

duction of its symbologies called Guidelines

for Producing Quality Symbols. By following

the membership application process and

adhering to the symbology production proce-

dures outlined by the UCC, the integrity of the

system as a worldwide enabler of commerce

is assured.

19, 20

See Appendix at the end of this chapter for contact information.

64 FLEXOGRAPHY: PRINCIPLES & PRACTICES

lmost all packages require

either a barcode or UPC sym-

bol for pricing, identification

and inventory information.

FIRST and ANSI have specifi-

cations that should be fol-

lowed. The difficulty for a designer who has

to use the UPC code in package design is

that the specifications for creating these

symbols are very strict and UPC codes

rarely, if ever, add to the appeal of an overall

design. So, not only do bar codes become a

necessary evil, but they also have a very

strict set of tolerances that must adhered to

by the designer and separator.

SIZE MATTERS

Some symbols are constrained by permis-

sible aspect ratios, especially those intended

for use with omni-directional scanners. Due

to the nature of this type of scan, these sym-

bols have a fixed relationship between their

height and width. When one dimension is

modified, the other dimension should be

altered by a proportional amount.

The EAN/UPC symbols are one such exam-

ple. Because of this relationship, EAN/UPC

symbols have a nominal height and width

specification. There is also a range of allow-

able sizes for the symbol, in this case from

80% to 200%. When specifying on purchase

orders, indication of size is generally referred

to as the symbol’s “magnification factor.”

Note: Temptation is everywhere. In order

to decrease the amount of space some sym-

bols take up on a design; designers may be

tempted to specify a decreased symbol height

without a corresponding reduction in

width. This process, called truncation, is not

permitted within the EAN/UPC symbologies,

as well as many others, and it should be

avoided.

It should also be noted that the allowable

magnification range can depend on how the

bar code will be used. For example, when

EAN/UPC symbols are used in conveyorized,

fixed-mount scanning environments (e.g.,

shipping and distribution) as well as at the

retail point-of-sale, the minimum magnifica-

tion allowed is increased from 80% to 160%.

An example of a point-of-sale product that

might also be used as a shipping container

would be a carton used for a large appliance,

(e.g., a television or microwave oven).

Finally, before the first ink is applied in

the pressroom, every press that will run bar

codes should be characterized. Press char-

acterization (or fingerprinting) is a prerequi-

site for producing quality bar code symbols.

Printers need to determine the minimum

size bar code a particular press can produce

with repeatable quality. They should ascer-

tain the correct bar-width reduction (BWR)

for bar codes in order to account for the

normal ink spread encountered during the

printing process. Once established, a printer

should not attempt to print bar codes out-

side these specified ranges.

For many years, printers used the

Printability Gauge illustrated in the UPC

Film Master Verification Manual, repro-

Bar Codes

in the Design Stage

BAR CODES 65

duced in Figure

. The Printability Gauge is

a series of dark bars arranged in a specific

pattern and is used to determine the range of

print gain. The range of press variance is

used to determine the minimum bar code

size (magnification) and the midpoint in the

range is used to establish the amount of

BWR (bar width reduction) that should be

made to the EAN/UPC symbol in prepress.

Both factors are determined based on a set

of tables that exist in ANSI/UCC1-1995:

U.P.C. Symbol Specification Manual.

Today, many companies have established

guidelines based on the process characteriza-

tion studies they have conducted with the

assistance of a film master manufacturer.

However the process of press characteriza-

tion may still be necessary in some cases. For

instance, a company may begin printing bar

code symbols for the first time or they may

begin utilizing new technology in design, film-

making, platemaking or printing. In cases like

these, they may choose to use the traditional

Printability Gauge method or a proprietary

method, but the basics remain the same. If

the printer chooses the print gauge method,

the printer needs to establish a range for bar-

width growth (press variance) and relate this

range to the bar-width tolerances specified in

the symbol specification. This will establish

the minimum size symbol they can produce.

They should then use the midpoint of the

range they encounter to make bar-width

reductions in the design stage.

COLOR IT BLACK

Color choice can be crucial. The optimum

color combination for bar codes is carbon

black bars with a white background. This

provides the highest degree of reflective dif-

ference between the bars and spaces, pro-

ducing an optimum read rate. Other colors

may be used but, in general, red is the color

of the scanner beam or light source most

often used to illuminate a symbol’s bars and

spaces, that in turn facilitates the decoding

or reading of a bar code. Whenever a scan-

ning beam reads a bar code symbol, it deter-

mines the presence of a bar or a space by

detecting whether or not the red light from

the scanning beam is being reflected from

the surface being illuminated by the beam. If

the beam illuminates a light color such as

white, or a color near the visible red spec-

trum such as orange and red, the area illu-

minated will reflect most of the red light and

will be decoded as a space. If the beam illu-

minates a dark-colored surface such as

black, dark blue, dark brown or dark green,

very little of the red beam will be reflected,

and this area will be decoded as a bar. That

is, there must be a sufficient contrast

between the reflected light from the dark

bars and light spaces.

The following guidance is provided for use

on opaque substrates:

• Bar code symbols require dark colors

for bars (e.g., black, dark blue, dark

brown or dark green). Red is an unac-

ceptable color for bars.

• The bars should always consist of a sin-

gle line color and should never be print-

ed by multiple imaging tools such as a

combination of process colors.

• Bar code symbols require light back-

grounds for the quiet zones and spaces

The Printability Gauge

contained in the UPC

Film Master Verification

Manual. The dark bars

are arranged in a

specific pattern, and are

used to determine the

range of print gain.