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

Barcode SYMBOLOGIES

3 LASER PRINTER

4 Bar Growth WRONG RIGHT Restrict scaling on the X dimension Undercut bars and grow spaces equally

5 Dirty Laser Printer CLEAN DIRTY Will not read OR Substitution Errors (CODE 39)

6 Bar Code Printing Future Trends Direct Part Marking Ink Jet Dot Peening Laser Etching

7 DPM Bar Code Reader n Laser to Illuminate n CCD to Read

8 Invisible (IR) Inks

9 IR Reading

10 Selecting a Bar Code Printer Environment Indoor vs. Outdoor Clean vs. Dirty Media Labels, Direct Marks, Paper Ruggedness Symbol Size Flexibility

Bar Code Reading

12 Definition Bar Code Reader A device used to extract the information that is optically encoded in a BCS and convert it into computer-compatible digital data Two devices: Reader & Decoder (sometimes packaged together as one) DATA PROCESSOR ELECTRO-OPTICAL SYSTEM SCANNING MEANS A/D CONVERTOR Reflected Light Illumination

13 READER FUNCTIONS 1.Find the correct elements 2.Determine the widths of each symbol’s bars and spaces 3.Quantize the element widths into the number of levels appropriate to the symbology used 4.Ensure that the quantized element widths are consistent with all of the encodation rules for the symbology 5.If necessary, reverse the data order 6.Confirm that quiet zones exist 7.Confirm that any check characters are consistent with decoded data

14 Electro-Optical System Light source creates “spot” on symbol Reader Captures and measures reflectivity Bars: Low Reflectivity Spaces: High Reflectivity LIGHT SOURCE TRANSMITTING LENS SYMBOL PHOTO DETECTOR APERTURE RECEIVING LENS (Focused Illuminator Design)

15 Analog-to-Digital Converter

16 Symbol Orientation Picket Fence vs. Ladder

17 Wavelength Reflectivity varies at different wavelengths Wavelength Match between Reader and Symbol Most Common Bands 633 nm 900 nm (infrared)

18 Specular Reflection Print symbols on diffuse, non-shiny, matte surface (e.g., paper) Avoid shiny surfaces (e.g., windows, laminates) Specular Reflection Diffuse Reflection

19 Specular Reflection SPECULAR REFLECTION

20 Avoiding Specular Reflection Do not print on mirrors or shiny surfaces Scan at an angle (<), not perpendicular to surface ( ) Quick Test: Hold symbol at shallow angle; bright reflection from Overhead light?

21 Bar Code Scanner (Most Commonly Used) Input Devices Wands Lasers CCD Fixed Mount