بنام خدا کاربرد کامپیوتر در مهندسی صنایع (21774( Lecture 9 The barcode

Barcode SYMBOLOGIES

3 DEFINITIONS Symbol: A parallel arrangement of varying width (or height) bars and spaces that encode data Code: Active data contained in a symbol (e.g., part #, serial #) Symbology: Unambiguous rules specifying the way data is encoded into bar and space widths (e.g., CODE 39, UPC)

4 QUESTION How do bar code scanners read information? Bars  dark (little light) Spaces  light (lots of light) Redundancy built into height

5 Symbol Structure Check Character

6 Symbology Characteristics -- Discrete vs. Continuous-- Discrete Continuous Each character stands alone Each character has bar on each end Adv  variety of printing techniques easier to read Disadv  larger symbols No intercharacter gap Each character begins with bar and ends with space Adv  Smaller Symbols Disadv  harder to print.

7 Symbology Characteristics -- Two Width vs. Multiple Width-- Two Width Multiple Width Wide & NarrowWidth determined by modules

8 Two-Width Symbology CODE 39 (Most Popular) “N” Ratio between wide and narrow element widths Ranges between 2.0 – 3.0 As N gets larger, printing tolerance increases

9 MULTIPLE-WIDTH SYMBOLOGY Bars and spaces can assume several different width values Modular Usually continuous Often decoded using edge-to-similar-edge algorithms to cope with bar growth problems

10 Symbology Characteristics -- Encodation Pattern— Numeric Alphanumeric ASCII

11 CODE 39 CHARACTER SET

12 Example of Encodation Interleaved 2 of 5

13 Example of Encodation What Number is Encoded in the Above I 2o5 Symbol? Answer:

14 FIXED vs. VARIABLE LENGTH

15 X DIMENSION The “nominal” width of the narrowest element Measured in mils (0.001″) Referred as “Z” when examining an unknown symbol CODE 39 CODE 128

16 START/STOP CHARACTER Indicates where symbol begins Indicates scanning direction bidirectional *CODE* CODE 39 CODABAR

17 CHECK CHARACTER Placed in a predetermined position in a symbol Value is based on algorithm of the other characters in the symbol Used by the scanner for validating that the correct data has been recorded

18 CHECK CHARACTER 1. Add all numbers in the odd positions starting with the number system number 2. Multiply the answer by 3 3. Sum the numbers in the even positions 4. Add Steps 2 and 3 together 5. Add a number to Step 4 that makes it evenly divisible by The check digit is added to the last data character Modulo Ten Check Digit

19 QUIET ZONE CODE 39 Quiet Zone 10x the X Dimension 0.25”

20 Symbology Standards UPC CODE 128 CODE 39

21 Universal Product Code (UPC) Standard for Retail Grocery Clothing Magazines OTC Drugs etc. Symbology & Coding Scheme Numeric only Continuous Multiple Width Fixed Length

22 CODE 39 First Alphanumeric Broad Industrial Use Hospitals (HIBCC) DoD Standard AIAG Standard Self Checking 128 Full ASCII Set Two Width, Discrete 5 Bars + 4 Spaces = 9 elements, of which 3 are wide and 6 are narrow Default: No Check Character

23 CODE 39 Significant Parameters Minimum X Dimension: inches Minimum Ratio of Wide to Narrow Elements 2.0:1 Maximum Ratio of Wide to Narrow Elements 3.0:1 Quiet Zones > 0.25 inches, or 10 x X Dimension

24 Inter-character Gap Between one and three times X dimension or at least inches Disadvantage: Low Density Substitution errors If No check character If Poor print quality CODE 39 Significant Parameters

25 CODE 128 Alphanumeric Symbology Encodes 128 Characters Continuous Symbology Multiple Element Widths Character: 3 bars, 3 spaces, 11 modules Question: What is the (n,k)? Advantage ==> High Density Three Possible Character Sets

26 CODE 128 UCC & EAN Standard for Shipping Containers for Apparel Industry and Distribution Voluntary Interindustry Commerce Standards (VICS) Standard for all containers in distribution

27 Selecting a Symbology Physical area available for symbol Type of data to be encoded Alpha? Numeric? Alphanumeric? Type of Printer Standards to which must be adhered

28 Symbology Future Trends Symbologies with Looser Tolerances Especially in Manufacturing Currently dealt with by making symbol larger Symbologies that hold more information in small space Especially in retail

29 DESIRABLE CHARACTERISTICS Large character set High reliability and easy to decode Able to be decoded using inexpensive equipment Easy to print Simple physical structure Broad tolerances High data security High information density

30 VARIETY OF SUBSTRATES Labels Tags Pages Forms Packages End Item Metals

31 Marking Bar Codes Non-intrusive marking methods Printing: Ink jet, Silk screen, stencil Molding, casting Intrusive marking methods dot peening Laser engraving Chemical etching

32 Symbol Printing Offsite Printing Used for high volume, identical or sequenced symbols Printed for subsequent use Onsite Printing (Demand Printing) Create symbols at time & place of usage Produce unique symbols on demand Printed via keyboard or attached computer

33 Off-Site Printing

34 Demand Printers Dot Matrix Thermal Thermal Transfer Laser Ink Jet Direct Part Laser Etch Pin Peening Invisible Ink

35 Dot Matrix Movable printhead, traversing from side to side Prints one character at a time Overlaps adjacent dot to produce approx. to straight edged bars Two types  Serial and Line X Dim  15 – 20 mils NEW RIBBON WORN RIBBON

36 Dot Matrix Advantage Inexpensive Disadvantage Great care needed in selection/maintenance of media/ribbon

37 Dot Matrix Printing

38 Thermal Printers Label Printer Uses heat sensitive coated substrate Printhead in direct contact with thermal substrate Printhead comprised of linear array of heater elements (e.g., 320 elements, 10 mil square)

39 Thermal Printers Advantages High image quality Flexibility (symbols, graphics, human readable) Disadvantages Limited to indoor applications Susceptible to smear Printhead wear

40 Thermal Printers Portable model

41 Thermal Transfer Printers Most popular printer choice Thermal ribbon between labels and printhead Advantages High Image Quality Flexibility (Symbols, Graphics, Human Readable) Resists Smearing Plain Paper Disadvantages Limited to Label Printing

42 THERMAL TRANSFER

43 Thermal Transfer Printers

44 Ink Jet Printers (Bubble Jet) Advantages High Resolutions ( dpi) (Not an advantage for bar code symbol printing) Low Cost Direct Marking Capability Disadvantages Ink Spread on some substrates

45 Laser Printers An optical image is transferred to a photosensitive surface by a controllable laser beam Toner particles attracted to charged surface Advantages High Image Quality Toner Particles adhered, not absorbed High resolution (600 dpi) Disadvantages Potential for “bar growth” due to auto scaling Dirty printer

46 LASER PRINTER