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

Barcode SYMBOLOGIES

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

Wands Advantage Low Cost Disadvantage Low Read Rates Acceleration QZ violation Scanning fast Scanning slow Hand Held, Contact Reader Scanning motion provided by operator Illuminates with light focused through aperature (spot), then reflected back

Laser Hand Held or Fixed Reader Most Popular Scanning provided by internal electromechanical system Fast Scan Times (< 1 sec.) High Read Rates (> 40 scans/sec)

Long Range Scanner Long Range Scanner

CCD Scanners (Charge-Coupled Device) Scans the received light path as a whole Image of BCS is optically transferred to a linear array of multiple adjacent photodiodes At least two photodiodes are covered by one narrow element (one Z length) Scans by electrically scanning each individual photodiode in a sequential manner

CCD Array of Photodiode Sensors Advantages Disadvantages Linear or Matrix Advantages No Moving Parts (Rugged) Less Expensive than Laser Smaller than Laser Disadvantages DOF < 1’’

2D CCD Reader

Fixed Mount, Moving Beam Scanners Used in untended environment (auto sortation, Mat. Handling) Internal scanning (40-100 scans/sec) Factors to control for 4-5 complete scanning opportunities Scanning line length Scanning rate Bar height Symbol orientation Conveyer speed

Fixed Mount Scanner

Reader Selection Criteria Number of Readers Cleanliness of Environment Cost Basic Reader Requirements Recommendation: Test various readers Read Rate - Read Time Ruggedness - Ergonomics

Two Dimensional Symbologies Module 6

Linear Symbologies Scan Path: Single Continuous Line Length = f(x, amount of data) Standard height equals 15% of the symbol’s length Problem: Required data exceeds physical space 4-20 characters “License Plate” Error Detection

Two-Dimensional Symbologies MaxiCode DataMatrix PDF417 High data capacities Space efficient Stores data file rather than lookup key Error Correction Currently over 24 2-D symbologies

Premise of 2-D Symbologies “To encode and print the largest amount of machine readable information in the smallest possible area”

2-D Main Issues How to keep track of rows. How to handle scan lines that cross between rows. How to detect and/or correct localized errors.

Structure --Stacked-- Data encoded in Linear Fashion Multiple Rows Often Rectangular Shape Scanned with Conventional Scanners S T A R L 1 O P d n-1 n-2 c k-1 k-2 QUIET ZONE ERROR CORRECTION AREA LEFT ROW INDICATORS RIGHT ROW DATA CODEWORD AREA

Structure --Matrix-- Represent binary code Array/Checkerboard Pattern Square in shape Perimeter Border/Center Target Read by determining color of each cell Uses CCD Reader Technology

Structure --Composite- Short and long messages The linear symbology decoded by conventional laser scanners the 2-D component decoded by CCD or rastering laser scanner Two different components of the overall symbol are linked

2-D Symbologies --Features-- Data Capacity Error Correction Orientation Independence Edge Independence

Data Capacity May contain up to 1800 characters in much smaller symbol

Error Correction Allow up to 50% of the symbol to be destroyed Typically utilize Reed-Solomon Algorithms for Error Correction

Orientation Independence Read at any angle (Matrix Symbologies only)

Edge Independence Do not depend on element thickness Allows printing/reading tolerances to be reduced Can print at microscopic level

2-D Symbology Standards MaxiCode DataMatrix PDF417 Currently over 24 different 2-D symbologies

MaxiCode Developed by UPS for Automatic Sortation & Tracking 1 in. square array with bullseye Finder Pattern 92 Characters: Fixed length, 596 bit with substantial redundancy Read Rate ==> 14 symbols/second Conveyor Speeds ==> 500 ft/min.

PDF417 Defacto standard for most hand held 2-D scanning applications Capacity: 3 to 90 rows; 1 to 30 char/row; 1,850 alphanumeric Characters Error Correction: Eight Levels Scan Time: < 1 second for many applications Used when Symbol Size is less of an issue

Typical PDF417 Applications Driver License Registrations U.S. Military ID Cards EDI Transactions Quality Conveyance Configuration Management Material Safety Data Sheets Warranty Claims

DataMatrix Checkerboard Arrangement of Black & White Squares Perimeter Border to id. symbol, cell location, orientation Can be read with contrast as low as 20% Two versions: ECC 000-140 and ECC 200 ECC 200: a 144 module square holds either 3116 digits or 2335 alpha chars Used for Small Component Marking Standard for the electronics industry

Commonly Asked Questions Are 2-D symbologies really useful? Do they, or will they, make linear bar codes obsolete? What are the 2-D symbologies good for?

Attributes of 2-D Symbologies Symbology PDF-417 Maxi Code Data Matrix AIM Standard Yes In Process ANSI MH10.8 Selected   Configuration Rectangle Square Element Magnification Variable Fixed Error Detecting Yes, strong Error Correcting Selectable or Fixed S, 9 levels S, 13 levels Data Capacity 1850 A/N 93 A/N 2335-3116 A/N Minimum Printed Element Size 0.0075² 0.0035² 0.006² Min. Etched Element Size 0.001² Label Printer Yes, many

Attributes of 2-D Symbologies Symbology PDF-417 Maxi Code Data Matrix Fixed Scanner Yes H-Held Scanner Yes, many Prototype Auto-distinguish with linear codes Yes, demo Design Focus Port. Data File General Purpose Handheld Scanning Sortation Small Components Strength AIM std. Strong Sponsor Exclusive for HH 30² DOF 500 ft/min Installed App. Recent Improv. Weakness Not for short data Not best suited for automatic scanning Fixed size Fixed Capacity No strong corporate sponsor