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1. 35 40 45 50 55 60 65 12 the scanning module 105 for the purpose of alerting the user to the completion of a successful decode attempt 4 3 3 Processor unit Processor unit 110 is preferably a solid state hand held electronic portable terminal for recording storing and trans mitting field data entered either through the scanning mod ule 105 via the interface cable 115 or from the user directly via the a keyboard 405 Processor unit 110 is provided with a microprocessor random access memory a gate array for implementation of all terminal logic a power management voltage regulation system of integrated chips and some analog circuitry for treatment of analog reflectivity data received from the scanning module 110 A customer replace able 32KB or 64KB EPROM custom application module is provided as an additional feature for changing the appli cation program 4 3 3 a Microprocessor Microprocessor is preferably of a type like the Hitachi 64180 This device is a Z 80 code compatible eight bit microprocessor with an on board memory management unit two UART s two sixteen bit timers an interrupt controller direct memory access circuitry and other features as dis closed in the Hitachi HD64180 Data Book January 1988 4 3 3 b Memory In one embodiment memory of three sorts is employed by the verifier of the present invention See Appendix C included in the parent application which issued as U S Pat N
2. Among the problems occurring as a result of faulty printing systems are insufficient contrast between bars and spaces collectively referred to in the art as elements of a bar code label unintentional bar width growth or loss due to ink spread or shrinkage ink voids or specs or other printing errors Bar code reading systems fail due to hard ware problems such as maladjusted or ineffective sensors emitters or processors in reading apparatus and in addition due to user mistakes such as improper positioning of the scanner relative to the bar code label of interest or improper programming of the processor in the reading apparatus For these reasons those who employ bar code systems often have need for a verification system which will effec tively identify existing or potential problems in the printing and reading systems thus allowing the user to adjust the bar code system to derive its maximum efficiency and perfor mance potential For example bar code printers might use a verification program as part of a quality control scheme designed to monitor print quality trends during the printing process and stop printing as bar codes begin to be printed out of specification Alternatively downstream bar code system users warehouse inventory managers for example might use information derived from a bar code verifier to alert him her to the need to print new labels for a group of products or to note bar code labels that will require sp
3. PRESS lt H gt FOR HELP STAT ILLEGAL BIT PATTERN PRESS lt H gt FORHELP FIG 8 FIG 8D SCAN MODULE 105 CONNECTOR 115 CPU EM 406 407 FIG 4B 5 504 315 Sheet 6 of 10 Apr 2 1996 U S Patent 313130 31Vadn j1V392 123135 1404 11035 140434 AULSNANI 140434 TVNINON SNOILVIA3Q SLN3W3HQSV3W 140434 LN3W313 140434 2ISV8 CEC SY J3l3IHJ3A U3LNIdd 1 41 0 51 0 f HOD Ges 0 SNOILdO JUVEWS SOIA 9vIV 8 SHVNW901 IISNV Ged Gel V1VI ISW NV3 I4N 69 6 9 8210 8002 A90108NWAS eS GIG VIVO A40 M3IA3H G 914 Scl v vi ISW NVP NV3 2dh 4v8vqgoo5 S2ILSON9VIQ 300930 GOS 1 981 5 504 315 Sheet 7 of 10 Apr 2 1996 U S Patent G09 GYVONVLS NOILYY9ITV AVY9 v9 914 009 JHV0ONV1S NOILVN8ITV2 MOVIE U S Patent Apr 2 1996 ANALYSIS SCREEN 1 10 11 89 10 38 AM Code 30f9 93 A ANALYSIS SCREEN 3A ELEMENT REPORT MIN AVG MAX WBAR 30 31 32 NBAR 11 12 14 WSPC 29 32 33 NSPC 10 12 14 PRESS lt H gt FOR HELP FIG 7C ANALYSIS SCREEN 4 XC EAGUREMENTS STI30F4 BAR SPC BAR SPC 12 15 12 43 15 12 Sheet 8 of 10 ANALYSIS SCREEN 2 BAR WIDTH RATI0 2 98 GROWTH LOSS 00 16 LMARGINRATIO GOOD RMARGIN RATIO GOOD PERCENT DECODE 100 CONTRAST 67 PRESS FORHELP ANALYSIS
4. SCREEN 38 ELEMENT REPORT MOD MIN AVG MAX RAT 1 2 14 16 2 26 28 302 00 3 40 42 443 00 4 54 54 54 3 88 PRESS lt H gt FOR HELP FIG 7D ANALYSIS SCREEN 5 DEVIATIONS STI3Z0F 4 Ben SPC BAR SPC 0 0 f 2 0 PRESS lt H gt FOR HELP FIG 7F 5 504 315 U S Patent Apr 2 1996 Sheet 9 of 10 5 504 315 FIG 9 200 U S Patent Apr 2 1996 Sheet 10 of 10 5 504 315 sweep FIG 10B 5 504 315 1 MEANS AND METHOD FOR NON CONTACT BAR CODE LABEL VERIFICATION This is a continuation of application Ser No 07 592 021 filed Sep 28 1990 now U S Pat No 5 218 190 TABLE OF CONTENTS BACKGROUND OF THE INVENTION 1 1 Field of the Invention 1 2 Description of Prior Art 2 SUMMARY OF THE INVENTION 3 BRIEF DESCRIPTION OF THE DRAWINGS 4 DETAILED DESCRIPTION OF SPECIFIC EMBODI MENTS 4 1 Overview of Verifier Operation 4 2 Functional Description 4 2 1 CALIBRATE 4 2 2 AUTO VERIFY 4 2 3 DECODE DIAGNOSTICS 4 2 4 REVIEW DATA 4 2 5 OPTIONS 4 2 6 USER ID 4 3 Hardware Setup 4 3 1 Scanning Module 4 3 2 Electrical Interface Cable 4 3 3 Processor unit 4 3 3 a Microprocessor 4 3 3 b Memory 4 3 3 c Gate Array 4 3 3 d Communications 4 3 3 e Analog Circuitry 4 3 3 f Other 4 4 Software Setup 4 4 1 Calibration 4 4 2 Software Generated Indices and Information 4 4 3 AUTO VERIFY Method 4 4 4 Reflectance Compensation for High Density Labels 5 CONCLUSION WHAT IS CLAIMED IS ABSTRACT 1 BAC
5. actually correspond to the bar code label area The bar code area is determined by the digital measurements and decode routine Bin wise contrast analysis is performed only on the analog data corresponding to the label itself Thus non bar code printing near the bar code label does not distort contrast ratings In general higher contrast levels correspond to better readability The high end of the contrast scale is represented by the contrast level derived by the scan of the black calibration standard There is low end contrast level below which the sensing means in the verifier scanning module is unable to reliably discern the difference in bars and spaces That level is represented by the contrast level recorded from the scan of the gray calibration standard Digital and Analog Processing An important aspect of verification is the ability of the verifier to accurately predict the readability of the bar code labels being tested Along these lines another feature of the present invention is a weighted index of five digital and analog factors that influ ence general readability of a bar code label Those five factors are Bar Width Ratio Percent Decode Margins and Digital Measurements Label Contrast The bar code label of interest is assigned a score from 0 to 100 for each of the factors In the index each of the five scores is weighted according to its absolute level Lower scores are more heavily weighted Table I Appendix
6. for a right to left or a left to right beam sweep along the laser path 1000 regardless of where in the beam path the bar code label 200 is placed Therefore without calibration the verifier has no way of distinguishing between a bar 20 mils wide placed six inches from the scan window 125 and a bar 40 mils wide placed twice as far away In addition as the dot sweeps back and forth the motor that drives the emitter varies in speed At either the left or the right end of the projected laser path 1000 the motor has zero velocity because it is turning around As it starts back toward the center of the laser path 1000 it accelerates to its maximum velocity before it reaches the middle of the scan beam 900 It begins to decelerate again before it eventually reaches a stop at the other end of the laser path 1000 This varying velocity further complicates the matter of absolute distance measurement without a calibration method The latter problem with non contact verification teach ing the verifier to properly measure contrast at a distance relates to the fact that incidental ambient lighting effects the way the verifier sensing means perceives light reflected from the bar code label Part of the rating of the readability of bar code labels depends on the contrast level the difference between the reflectivity level of the bars 205 and that of the spaces 210 that comprise the label 200 Contrast differences are frequently taken into account
7. in the design of the optical system in a verifier but the contrast problem can usefully be addressed in the calibration process as well In order to avoid inconsistencies in measurement of distances and contrast the present invention provides a software calibration method by which these two non contact problems are corrected At the user level calibration consists of selecting CALIBRATE MODE 505 and then scanning a black calibration standard 600 and a gray calibration stan dard 605 in response to prompts from the verifier Then internally to the verifier the distance by which the scanning module is removed from the bar code label is 5 504 315 15 determined by observing differences in the perceived widths and spacing of bar code elements on the black and gray calibration standards 600 605 all of which elements are or known equal size and placed at equal distances from one another The data points acquired by the calibration scan operations are divided into zones called bins 256 bytes comprising each bin which represent reflectivity data acquired in equi time sweep segments The true absolute widths or the calibration standard elements are stored in memory accessible to the processor In one embodiment each pair of adjacent transitions and therefore each bar or space is 30 mils wide Bins usually hold two or three transitions The conversion of bar code element data from time to distance units can thus be readily accomplish
8. mode 505 prompts the user to scan the bar code label of interest and subsequently presents a diagnostic report based on a data derived from that scanning attempt compared with b standard profile data e g data concern ing element widths margins tolerances number of transi tions etc for various bar code label classes Code 39 etc stored in the memory unit 407 FIGS 7 show the 5 504 315 9 series of screens that would be used to report diagnostic information derived from a bar code label scan The user may use the OPTIONS mode 525 choice to customize the information reported as well as the form in which it is reported It will be apparent from the discussion in subse quent passages how the verifier processor derives the infor mation reported in the diagnostics report from the digital and analog reflectivity signals FIG 7A shows the processor unit monitor Analysis Screen 1 on which the verifier reports The date and time of the analysis The symbology code type of the scanned bar code label The encoded data content of the scanned bar code label The scannability trend index STD a weighted value of readability based on fat thin element measurements percent decode and contrast and The American National Standards Institute ANSI speci fication grade assigned to the scanned bar code label FIG 7B shows processor unit monitor Analysis Screen 2 on which the verifier reports Ratio of wide to narrow labe
9. or orders to accomplish substantially the same results and objects Accordingly any description of arrangements of equipment and methods given in the following or preceding explanation should be understood to be illustrative and exemplary in nature and is not intended to be self limiting in any manner whatsoever An example of a verifier employing features of the present invention in one exemplary embodiment is the Laser Chek LI by Symbol Technologies Inc As an aid to understanding the present invention the User Manual for the Laser Chek is included as Appendix D in the parent application which issued as U S Pat No 5 218 190 hereby incorporated by reference Additionally source code for the Laser Chek II software is included as Appendix E in the parent application which issued as U S Pat No 5 218 190 hereby incorpo tated by reference 3 BRIEF DESCRIPTION OF THE DRAWINGS FIG 1 shows in general an exemplary specific embodi ment of the present invention FIG 2 shows an enlarged view of a bar code label FIGS 3A 3G show the effects of signal processing on the raw reflectivity signal derived by verifier sensing means FIG 4A shows generally an exemplary specific embodi ment of the present invention as arranged during operation FIG 4B is a block diagram of certain components of the embodiment FIG 5 shows an exemplary menu structure for the verifier of the present invention FIGS 6A amp 6B illustrate ge
10. such inaccuracies 10 15 20 25 30 35 45 50 55 60 65 4 When a target label is subsequently scanned for verifica tion a map of perceived widths of a target label is likewise generated the verification scanning is performed under ambient conditions similar to the calibration pattern scan and at the same standard distance Applying the previously computed correction factors to the information represented in the map results in a more accurate representation of the target label In one embodiment the verifier calibrates itself for arbi trary but constant lighting conditions affecting its operation The two bar code calibration standards used for measure ment calibration are of different contrast levels both levels known to the verifier software By scanning both calibration standard labels the verifier creates a contrast scale against which contrast levels derived in the normal operation of the verifier are compared Once calibration has been performed for a specific scanner module orientation distance and angle relative to the bar code label of interest the verifier is ready for operation in its normal mode Alternatively of course a single calibration standard may be used According to another feature of the present invention methods are provided for identifying and decoding bar code labels and subsequently issuing diagnostic reports charac terizing their readability A target bar code label sca
11. verifying a reflectivity characteristic of a target symbol when the target symbol is positioned at a substantial distance from the verifier apparatus the target symbol being of the type including a pattern of elements having less reflective areas and more reflective areas said method comprising the steps of providing calibration information to a verifier apparatus positioning the verifier apparatus including a radiation emitter and a radiation detector at a predetermined substantial distance from the location of said target symbol directing radiation from said emitter to a plurality of points on said target symbol comprising scanning a beam of radiation across said target symbol at a vari able scan rate receiving radiation reflected from said target symbol processing the received radiation to generate reflectivity data representing reflectivity conditions at a plurality of points on said target symbol using the calibration information to compensate the reflectivity data to provide compensated reflectivity data said calibration information including informa tion for compensating for said variable scan speed and processing the compensated reflectivity data to provide a measurement of said reflectivity characteristic 2 The method of claim 1 wherein the calibration infor mation comprises information for compensating for the predetermined substantial distance at which the target sym bol is positioned 3 The method of
12. A included in the parent application which issued as U S Pat No 5 218 190 hereby incorporated by reference shows the scheme for varied weighting of the factors Pseudo code Appendix B included in the parent application which issued as U S Pat No 5 218 190 hereby incorporated by reference reflects the weighting scheme 4 4 3 AUTO VERIFY Method As disclosed a verifier according to the present invention comprises a feature by which a bar code label is identified as belonging to a particular symbology and is decoded without a priori knowledge of the symbology type In the specific embodiment described heretofore this feature is called AUTO VERIFY mode 515 In AUTO VERIFY mode 515 the verifier automatically identifies a scanned bar code label as belonging to one of the known symbologies enabled for identification by the user The method used to identify the symbology of and decode a bar code characterized by binary digital data derived from a scan operation is implemented as a software function performed in the processor unit The method for AUTO VERIFY is 1 Locate bar code label data among scan data by identifying bar code margins 2 Count number of binary digital transistors between bar code margins and eliminate symbologies requiring dif ferent numbers of transitions and 10 15 20 25 30 35 40 45 50 55 60 65 18 3 Attempt to decode bar code character by character for symbol
13. CII data from any other peripheral device may be input into the built in UART in the microprocessor The analog reflectivity signal derived in the scanner module 105 is not handled by the ESID interface It is handled instead by analog circuitry in the terminal as described below 4 3 3 e Analog Circuitry According to one feature of the present invention means are provided for measuring reflectivity contrast characteris tics of bar code label 200 As previously described an analog signal which represents the non discrete reflectivity levels perceived by scan means is derived by the scanner module 105 That signal appears at one of the contacts coming down interface cable 115 and varies between zero and three volts peak according to the character and compo sition of the bar code label of interest 200 In the processor unit 110 this signal is called VIDEO The VIDEO signal goes from the interface cable 115 to a differential amplifier The differential amplifier configura tion effectively nulls out any common mode noise that comes into the processor unit 110 with the desired signal The amplifier multiplier function increases the amplitude of the signal by a factor of 1 5 so that an analog signal varying between zero and four and one half volts is directed into a digitizer chip A state machine drives the digitizer with the proper timing for sampling the analog input at the highest possible rate consistent with the microprocessor speed Da
14. CODABAR IATA 125 D25 IATA 25 025 C93 UPC EAN JAN MSI SELECT CREATE UPDATE DELETE PRINTER VERIFIER MEMORY RS 232 SERIAL PORT BASIC REPORT ELEMENT REPORT MEASUREMENTS DEVIATIONS NOMINAL REPORT INDUSTRY REPORT 5 504 315 Sheet 1 of 10 Apr 2 1996 U S Patent 100 TERE aa 111119 EB Basen EB FIG 1 5 504 315 Sheet 2 of 10 Apr 2 1996 U S Patent 913 NI9u V W 3 1381 3009 4V8g n O X NI9UVIA U S Patent Apr 2 1996 Sheet 3 of 10 5 504 315 FIG Lali PT BAR CODE LABEL FIG 3C AU LWT DIGITAL SIGNAL uscocsqoooeo TIMED TRANSITION INTERVAL FIG BBall BAR CODE LABEL ss LU gee aoc sos 5 504 315 Sheet 4 of 10 Apr 2 1996 U S Patent 1 A184 elele esse FIG 4 U S Patent Apr 2 1996 Sheet 5 of 10 5 504 315 SELECT SYMBOLOGY gt gt CODABAR MSI CODE 11 DECODE DIAGNOSTICS SCAN CODE 3 OF9 TO BE ANALYZED INTERLEAVED 20F5 DISCRETE 20F 5 CODE 39 EAN JAN 8 FIG 8A FIG 8B CODE 30F9 01234567 CODE 3 OF 9 ONO4000 aec A A CHARACTER START STATUS G00D
15. HIT T LANE I UN US005504315A United States Patent Patent Number 5 504 315 Hardesty et al 45 Date of Patent Apr 2 1996 54 MEANS AND METHOD FOR NON CONTACT 4 795 281 1 1989 Ulinksi et al 235 432 BAR CODE LABEL VERIFICATION 4 860 226 8 1989 Martin et al w 364 552 4 894 790 1 1990 Yotsuya et al 364 552 75 Inventors John Hardesty Ervine Calif Edward x es v d xp SA 067 zybylowicz et al u en 5 194 720 3 1993 Reinnagel et al urnnnnnuns 235 437 Viejo Timothy ee Fi 5 218 190 6 1993 Hardesty et al 235 462 Ana both of Calif FOREIGN PATENT DOCUMENTS 73 Assignee Symbol Technologies Inc Bohemia 55 88172 7 1980 Japan N Y OTHER PUBLICATIONS Notice The portion of the term of this patent Quick Check 500 brochure Photographic Sciences 2 subsequent to Jun 8 2010 has been pages 1989 disclaimed Barkan Automatic I D News Author verifies the key to bar coding success Nov 1988 21 Appl No 59 252 Primary Examiner Robert A Weinhardt 22 Filed May 7 1993 Attorney Agent or Firm James H Beusse 57 ABSTRACT Related U S Application Data A portable conveniently usable and inexpensive non con 63 Continuation of Ser No 592 021 Sep 28 1990 Pat No tact bar code verifier permits testing of bar code labels at 5 218 190 some a
16. KGROUND OF THE INVENTION 1 1 Field of the Invention In inventory intensive wholesale and retail operations bar coding systems have become popularly employed in track ing the flow of products Bar coding systems frequently include not only printing and reading equipment but also means for verification Verification is a process by which a bar code label is analyzed to determine if it has been printed in accordance with print specifications dictated by the par ticular bar code symbology e g UPC Code 39 MSI Plessey etc and industry group e g ANSI LOGMARS IATA etc against which it was printed The present invention relates generally to optical scanning systems for use in bar coding systems More particularly the present invention relates to portable non contact bar code verifier arrangements and method by which the quality and readability of scanned bar code labels are measured ana lyzed and reported in a convenient and inexpensive way 1 2 Description of Prior Art The advantages of bar coding systems are well known In order for a bar code system to effectively handle inventory information it must comprise at least two properly func 10 15 20 25 30 35 45 50 55 60 65 2 tioning subsystems code printing system and bar code reading system It is the shortcomings in either or both of these two subsystems that often necessitate a third a bar code verification system
17. analog and digital data sets decodes and identifies the scanned bar code label and yields a plurality of indices characterizing its readability and print quality 4 2 Functional Description In operation a bar code verifier 100 according to the present invention functions as described hereinafter FIG 4A shows the bar code verifier 100 as connected and situated during normal operation The processor unit 110 interface cable 115 and scanning module 105 are function ally connected The scanning module 105 is preferably hand held by the user and means are provided for attaching the processor unit 110 to the user s belt for portability and convenience in use The trigger 120 is activated by the user and serves to initiate a scan operation once the scanning module 105 has been properly positioned above the bar code label 200 of interest An important feature of the present invention lies in the ability to make measurements at arbitrary but constant orientation of verifier scanner module 105 relative to the bar code label 200 of interest In order to assist the user in maintaining constancy of scanner module orientation a plexiglass scanner module trainer 400 is provided The scanning window end of the scanning module 105 fits into a receptacle slot 402 on the trainer 400 The base 404 of the trainer 400 rests on a surface in the same plane as the bar code label 200 of interest The trainer 400 provides a convenient way of maintaining a partic
18. ans The data series are stored in random access memory RAM using direct memory access DMA operations From RAM the data are accessible to the verifier processor and become the basis for a number of software functions performed and indices derived by the processor In accordance with the non contact feature of the present invention a method is provided by which the verifier software calibrates its measuring parameters to compensate for an arbitrary but constant distance and angle of the scanner module comprising emitter and scan means rela tive to the bar code label of interest Calibration is accom plished by scanning one or two calibration standard patterns of known element bar and space size and print quality Notably the verifier analyzes the reflectivity data received from scanning a calibration standard pattern under then ambient conditions at an arbitrary standard distance to determine reflectivity data corresponding to a plurality of points on the calibration standard pattern The verifier uses the calibration standard data to develop a map of the perceived widths of the various bars and spaces comprising the calibration standard pattern These perceived widths can be rendered less than optimally accurate by e g variations in scanner motor speed The actual widths of the calibration pattern bars and spaces are known however this enables the verifier to compute appropriate correction factors to com pensate for
19. ar code readability under various reading conditions affecting noncontact type readers Sec ond analysis of quality and readability of bar code labels in prior art verifiers has not been as descriptive and instructive as often desired Third prior art verifiers have not had the added capability of being usable as bar code readers Fourth prior an laser based verifiers have generally not been con veniently portable due to their large size Fifth prior art verifiers have been expensive due to their large number of components required for signal processing Finally due to the use of separate technology for verification and reading bar code verifiers have not been accurately predictive of a reader s ability to read a particular bar code label 5 504 315 3 2 SUMMARY OF THE INVENTION The present invention overcomes some of the drawbacks of the prior art A portable conveniently usable relatively inexpensive non contact bar code verifier is provided which will test bar code labels removed some arbitrary but con stant distance from the verifier The bar code verifier can calibrate its operation according to the distance by which it is removed from the bar code label being analyzed The calibration approach helps compensate for variations e g the motor speed of the verifier scanner subsystem and other verifier characteristics Further according to the present invention means are provided for analysis of print contrast quality
20. aracterizes the relative spatial relationships between bars and spaces comprising the bar code label of interest 200 As explained previously this signal is timed in the terminal to determine relative temporal relationships between bars and spaces which relationships can later be converted to abso lute spatial relationships using data acquired during calibra tion The analog VIDEO signal is the analog reflectivity signal exactly as it comes from the scan means Terminal processing of the analog VIDEO signal is described below under Analog Circuitry The start of scan edge signal originates in the scanning module 105 and is used to mark the start of a left to right or right to left laser beam sweep This signal is vital to proper terminal interpretation of the digital and analog reflectivity data coming from the scanning module 105 The trigger signal is used by the scanning module 105 to signal the processor unit to turn ON the laser beam in response to depression of the trigger 120 by the user The laser beam enable signal originates in the processor unit 110 in response to the receipt of the trigger signal from the scanning module 105 This signal enables the laser beam for a bar code label scan in response to depression of the trigger 120 by the user The decode LED signal originates in the processor unit 110 and is used to control a light emitting diode LED on 10 20 25 30
21. arbitrary but constant conditions under which it will verify bar code labels in normal operation state Finally a normal operation state is provided for scanning bar code labels of interest In normal operation flight reflected from a subject label 200 is sensed by scan means located in scanning module 105 behind scanning window 125 Conventional signal processing occurs locally to the scanning module 105 and in the unit 110 and results in twenty eight series of data points each series corresponding to a binary digital representation of the light reflected from the bar code label during one emitting means sweep FIG 3A illustrates the step by step effect of processing on the raw reflectivity signal derived from scan means An analog to digital converter located in the scanning module converts the analog signal into a binary signal Subsequently in the unit 110 that binary digital signal is converted to a time based count of relative per ceived transition widths That is a clocking digitizer creates discrete data points corresponding to the perceived time spacing between reflectivity level transitions Only a repre sentative number of points are shown in FIG 3A for illustration It will be understood that one data point will be created by the clocking digitizer for each transition per ceived It will further be appreciated that the series of data labeled Time Transition Intervals is representative of the relative distance between reflec
22. claim 1 wherein said steps of providing calibration information and using the calibration informa tion comprise the steps of placing at least one calibration standard at the location of said target symbol said calibration standard including a pattern of elements having less reflective areas and more reflective areas directing radiation from said emitter to a plurality of points on said calibration standard receiving radiation reflected from said calibration stan dard 20 30 40 45 50 55 65 20 processing said received radiation to produce measured characteristics of said calibration standard comparing said measured characteristics of said calibra tion standard to known characteristics of said calibra tion standard generating correction factors based on said comparison using the correction factors to compensate the reflectivity data 4 The method of claim 3 wherein one said measured characteristic of said calibration standard is the distance between two elements i 5 The method of claim 3 wherein said measured charac teristics of said calibration standard are the same character istic measured at different positions along said calibration standard and said correction factors include correction factors for different positions along said target symbol 6 A method of measuring a characteristic of a target symbol which is positioned at an arbitrary distance from a verifier apparatus the target symb
23. d to scan bar code labels of interest and subsequently generate information characterizing them In AUTO VERIFY mode 515 the verifier automatically dis criminates between symbologies currently enabled for searching and issues a diagnostic report on the type content teadability and print quality of the scanned bar code label DECODE DIAGNOSTICS mode 510 is used to derive similar information when the user already knows the sym bology of the bar code label of interest In REVIEW DATA mode 520 the verifier is functional to review saved analysis sessions performed under AUTO VERIFY mode 515 OPTIONS mode 525 functions to allow the verifier user to select certain verifier features of diagnostic considerations and actual contents of the diagnostic reports USER ID mode 530 allows the user to select create or delete specific user identification codes 4 2 1 CALIBRATE According to the non contact feature of the present inven tion bar code label 200 may be scanned by the scanning module 105 removed some arbitrary but constant distance and oriented at some unknown but constant angle relative to the label 200 Calibration of the verifier for the arbitrary conditions is accomplished by means of a calibration routine in which one or more calibration standard bar code labels of known element bar and space dimensions and spacing and print contrast is scanned In order to ensure the accuracy of bar code diagnostics reporting the user calibrates th
24. dices and Information Once the verifier software has been taught via calibra tion how to measure distances and contrast levels against 10 15 20 25 30 35 40 45 50 55 60 65 16 known standards a number of indices that characterize quality and readability of bar code labels can be calculated for scanned bar code labels of interest In AUTO VERIFY or DECODE DIAGNOSTICS mode the verifier acquires twenty nine series of data twenty eight digital and one analog which represent the reflectivity levels perceived by the sensing element in the verifier scanning module Ideally the twenty eight digital sweeps should contain identical measurements In reality chances are that they will vary slightly from one to another The first twenty six data series are used strictly to derive percent decode as shown herein after The next data series the twenty seventh and twenty eight are used for all other digital calculations The final data series the twenty ninth is the analog series and is used for contrast analysis as disclosed hereinafter Software routines derive a plurality of indices from the digital data analog data and a combination of analog and digital data Digital Processing Binary digital reflectivity data yield the following indices and information about the bar code label of interest Absolute widths of elements bars and spaces Average absolute widths of wide and narrow elements bar
25. e label of interest and subse quently to scan the bar code label As before the verifier compares scanned data from the bar code label with standard profile data for various bar code label classes stored in the memory unit 407 FIG 8A shows the screen that so prompts the user FIG 8B prompts a scan operation which may be initiated by the user If the bar code label scan is successful the verifier will issue a diagnostics report as shown in FIG 8C That report indicates the code type of the bar code label the encoded data content and a general readability index of the label In the event of an unsuccessful decode attempt the verifier may issue a partial diagnostics report as shown in FIG 8D which delineates as much of the diagnostics data as possible and indicates why the decode attempt failed 10 20 30 35 40 45 50 55 60 65 10 Possible reasons for a DECODE DIAGNOSTICS decode failure include No start stop character Bad check digit Margin out of specification Bad character placement Minimum Reflective Difference contrast below read ability Incorrect number of data characters 4 2 4 REVIEW DATA A REVIEW DATA mode 520 selected from the verifier main menu allows the user to review diagnostic reports from previous AUTO VERIFY scans To make the diagnostic reports available for review by REVIEW DATA mode 520 the verifier internal memory must be enabled through the OPTIONS 525 main menu c
26. e verifier before its first use and subsequently re calibrates whenever the verifier orien tation distance and angle relative to bar code labels of interest is changed In one embodiment when CALIBRATE mode 515 is selected the verifier prompts the user to scan first the black calibration standard 600 shown in FIG 6A followed by the gray calibration standard 605 shown in FIG 6B Alternatively the verifier control software may be designed so that only a single label is scanned Once this is done the verifier calibration for that scanning orientation is complete Scan distance and angle must remain relatively constant in subsequent scans performed in AUTO VERIFY mode 515 or DECODE DIAGNOSTICS mode 510 Scanner module trainer 400 may be employed as one way of ensuring this Upon repositioning the scanner must be re calibrated for the new scan distance and angle Software components of the calibration system will become apparent hereinafter 4 2 2 AUTO VERIFY A verifier according to the present invention operating in AUTO VERIFY mode 515 performs diagnostics tests based on reflectivity information derived from the scan of a particular bar code label of interest If calibration has not occurred choosing AUTO VERIFY 505 from the menu leads directly to the unit monitor 410 displaying a prompt message requesting that the user calibrate before diagnostic scanning can occur After calibration has occurred the verifier operating in AUTO VERIFY
27. ecial handling as they move through the system An article by one of the present inventors on the subject of bar code verifica tion is instructive in pointing out potential bar code prob lems and potential verification solutions See Opinion by Tina Barkan at Automatic News November 1988 Previously two types of verifiers both requiring contact of the scanner with the bar code label have been employed The first a contact wand uses a light emitting source at the end of a pencil looking wand which is guided manually over the bar code label by the user Light emitted from the light source is reflected by the bar code label pattern and received by a detector also in the wand This type of verifier requires a single pass of the wand over the bar code label to check the label and acquire the appropriate information A second type of prior art verifier is the laser based verifier which also requires contact between the head of the scanner unit and the bar code label However the laser based verifier checks the bar code label multiple times as the laser beam sweeps rapidly back and forth across the label The known optical scanning verifier systems have not proven to be altogether satisfactory for a variety of reasons First contact type verifiers are inconvenient Furthermore by virtue of the fact that they am designed to block out ambient lighting conditions contact type verifiers are not accurately predictive of b
28. ecify a particular industry group standard which will be applied to the bar code diagnostics analyses performed in AUTO VERIFY or DECODE DIAGNOSTICS mode Clock Through this choice the user may initialize the time and date so that diagnostic reports can include time and date of testing Reports Through this choice the user can customize the form of the diagnostic reports issued by the verifier operat ing in AUTO VERIFY mode 515 Any of the Analysis Screens shown in FIGS 7A 7E can be selectively enabled disabled by the user Output Through this choice the user is allowed to select the destination of the diagnostic report output Available choices include output port 415 printer port 420 and internal memory 4 2 6 USER ID In USER ID mode 530 a verifier operating according to the present invention allows the user to select create or delete user identification passwords for storing and retriev ing individual customized verifier options selected in a session 4 3 Hardware Setup 5 504 315 In one embodiment of the present invention a bar code label verifier 100 comprises a scanning module 105 for directing a beam of radiation at a subject bar code 200 and for receiving reflected radiation representative of the con stituency of the bar code label 200 Verifier 100 further comprises a processor unit 100 operatively connected to scanning module 105 by means of an electrical interface cable 115 The processor unit 110
29. ed by the processor As an example a particular bin might contain two adjacent transitions which are 150 data points data points being acquired at equi time intervals apart Since it is known that the transition to transition width should be 30 mils a conversion factor of 150 to 30 or 5 to 1 data points to mils is calculated for that bin The conversion factors different for each bin are stored for use in normal operation AUTO VERIFY or DECODE DIAGNOSTICS modes Once the verifier has been calibrated for a particular scan distance it converts data characterizing temporal relation ships it acquires through the sensor into data reflecting spatial relationships and further into absolute distance data by use of this conversion scheme In addition contrast levels perceived by the scan means during the calibration scan operations can be compared to expected contrast levels for the known black and gray calibration standards 600 605 and subsequently measure ment sensitivity can be adjusted for the ambient lighting conditions affecting the verifier scan means Contrast levels are measured for the calibration standards 600 605 by again dividing the scan sweep into zones or bins each com prising 256 bytes and finding the difference between the darkest least reflective and the lightest most reflective points in each of the bins The black bars on the black calibration standard 600 represent absolute black or as close to it as is po
30. ence level As known in the art security levels reflect the confidence a decoder can have in the accuracy of a particular decode attempt With higher security level codes the decoder has a greater level of confidence that if the bar code is decoded to yield particular data contents those contents are correct Therefore the user can have a greater degree of confidence in the final answer If a character cannot be decoded using the conventions of a particular symbology that symbology is abandoned and the verifier software moves on to check the next symbology in the security level table In the event of a decode attempt still unsuccessful after all possible symbologies have been exhausted the verifier reports an unsuccessful decode attempt and lists as much information about the label as is possible It will be recognized that at the completion of this three step AUTO VERIFY routine the software will have not only identified the symbology of the scanned bar code label but also decoded its data contents 4 4 4 Reflectance Compensation for High Density Labels The accuracy of scan data can be reduced if the width of an element bar or space of a bar code label is less than the spot size of the laser beam because the radiation reflected from such an element is less than from e g an element that is wider than the spot size In an embodiment of the present invention this factor is taken into account by increasing the computed reflectance
31. et al issued Jan 30 1990 The laser beam sweeps back and forth rapidly in a motion horizontal to the long axis of the rectangular scanning window 125 shown from the side FIG 2 shows generally a bar code label 200 As emitted laser light impinges on a remotely located bar code label 200 it is reflected to varying degrees by the bars 205 and spaces 210 comprising the bar code label 200 Refiected light is detected by a radiation sensitive scan means also located behind scanning window 125 Said scan means functions to produce an analog electrical signal proportional to the intensity of radiation impringing upon it In order to calibrate verifier operation for the unknown distance and angle of the emitting means and scan means relative to the subject bar code labels a calibration routine is executed which entails the user scanning two calibration standard labels of known characteristics The perceived widths and contrast of bars and spaces constituting the calibration standard labels are compared to previously stored known widths and contrast in order to derive conversion factors to be used subsequently in relating relative scan data to absolute distances and contrast levels Three states of operation are provided for verifier opera tion A programming state is provided for use in allowing verifier users to alter and customize verifier operational parameters A calibration state is provided by which users will calibrate the verifier for the
32. f margins rating Calculation of weighted scannability index A verifier processor unit is preferably equipped with output means including a display screen printer terminal and a scrim output port Input means comprising a keyboard are also provided Processor software functions are menu driven to enable the user to determine the mode of operation of the verifier Additional hardware features of the present invention include a scanner gun trainer for standardizing scanner orientation relative to bar code labels of interest visible laser based diode emitter means use of direct memory 5 504 315 5 access hardware internal to microprocessor to acquire laser scan information digital and analog use of custom application modules for switching applications Additional software features of the present invention include downward application of the verifier as a bar code reader certain software generated print quality and read ability indices which are new to the art Information derived by the verifier of the present inven tion may be stored and or employed in control and analytical functions related to bar code system quality as commonly recognized in the art These and other features of the invention will become apparent hereinafter It will be understood that the present invention comprises many separate novel features which can be employed individually or in combination and can be arranged in various configurations
33. gions to either side of the bar and space sequence in a bar code label are shown in FIG 2 According to the various symbology specifications they are set at certain absolute or relative widths but are always wider than any other bar code elements by some set mul tiple Margins are identified by the software of the present invention as positions where there is a wide to narrow ratio of adjacent elements that exceeds 6 to 1 Percent decode is standard index reflective of probability that a single scan of a bar code would result in a successful decode In a well designed bar code scanning system that number will approach 100 Percent decode is determined by attempting to decode each of the first twenty six digital data series and then determining the percent of those attempts ending with a successful decode 5 504 315 17 Analog Processing Analog processing consists con trast analysis Analog reflectivity data are analyzed bin wise as in the calibration operations for the highest and lowest reflectivity level in each bin The contrast is the difference between the highest and lowest reflectivity value The perceived contrast in each bin is converted to actual contrast using the scale and method outlined above The average of the bin wise contrast is the contrast for the entire bar code label In order to avoid inaccurate contrast ratings due to periph eral label print the verifier analyzes only analog data that
34. hoice as can be seen from FIG 5 Selecting REVIEW DATA mode 520 from the main menu immediately calls up to the processor unit monitor 410 the first screen of the diagnostic report for the last label scan performed under AUTO VERIFY mode 515 Other diag nostic report screens may be retrieved by the user by appropriate input commands issued through the processor unit keyboard 4 2 5 OPTIONS An OPTIONS mode 525 selected from the verifier main menu allows the user to customize the operation of the verifier in regard to the symbologies recognized the indus try group standards to be applied to the diagnostic analyses clock operation form of diagnostics reports and selection of diagnostic report output Symbology Through this choice the user may define which symbology types and variants will be diagnosed by the verifier operating in AUTO VERIFY or DECODE DIAGNOSTICS mode If the symbology is a variable length code the user may specify the lengths to be diagnosed Legal symbologies might include but not be limited to UPC EAN JAN CODABAR IATA 125 D25 C39 C93 C128 For UPC code types for example after choosing the symbologies the user is prompted to choose among the following UPC variants UPC A UPC E EAN 8 EAN 13 SUPP 2 or SUPP 5 Similarly having selected a multi length symbology the user is prompted to selectively enable or disable the various code lengths available Industry Group Through this choice the user may sp
35. in bar code labels Additionally a bar coder verifier is provided that can also function as a bar code reader Also according to the present invention means are pro vided for verifying a bar code label using a wavelength of light and scanning technology similar to those that will subsequently be used by reading apparatus Additionally means are provided for determining the absolute dimensions of bar code label elements The present invention includes bar code label verifier apparatus for use in measuring and analyzing the quality and readability of printed bar code labels target labels The apparatus includes means for acquiring digital and analog information characterizing a bar code label sometimes referred to herein as reflectivity data coupled with means for processing and analyzing that information and for reporting bar code label readability and print quality indices as derived from the analog and digital information Visible laser light emitted by verifier emitter means is reflected from a series of white comparatively more reflective spaces and black comparatively less reflec tive bars comprising a bar code label and subsequently is received by verifier scan means Raw signal processing means yield a series of data corresponding to analog reflec tivity levels as measured by said scan means and other series of data corresponding to binary digital reflectivity levels as measured by said scan me
36. l elements bars and spaces Element growth loss deviation from expected widths Left and right margin status Percent decode the number of expected successful decodes of the label in 100 attempts and Minimum reflectance difference contrast FIG 7C shows two possible processor unit monitor Analysis Screens 3 labeled 3A and B on which the verifier reports wide narrow element attributes The contents of this report might vary according to the symbology of the bar code label of interest as can be seen on the two different example screens FIG 7D shows processor unit monitor Analysis Screen 4 on which the verifier reports absolute bar space measure ments for each character FIG 7E shows processor unit monitor Analysis Screen 5 on which the verifier reports deviations from average for the element widths each character In the event of an unsuccessful decode attempt in AUTO VERIFY mode 515 the verifier issues diagnostic reports like those in FIGS 7 that indicate failure of the verifier to read the label and as much other information as is possible 4 2 3 DECODE DIAGNOSTICS In DECODE DIAGNOSTICS mode 510 a verifier accord ing to the present invention analyzes reflectivity data gath ered during a scan of a bar code label of known symbology and issues the user a general diagnostics report After selecting DECODE DIAGNOSTICS mode 510 from the verifier main menu the user is prompted to select the symbology of the bar cod
37. may be a solid state hand held electronic portable terminal for recording stor ing and transmitting field data entered either through the scanning module 105 via the interface cable 115 or from the user directly via the keyboard 405 Alternatively the pro cessor unit 110 and scanning module 105 may be con structed as an integral unit 4 3 1 Scanning Module The scanning module 105 is preferably a derivative of the publicly available LS 2000 scanner gun manufactured and distributed by Symbol Technologies Inc the assignee of this invention aspects of this scanner gun are described in the aforementioned U S Pat No 4 897 532 Portable Laser Diode Scanning Head by Swartz et al modified scanner board allows scanning module 105 to acquire analog reflec tivity data and transfer it to the processor unit 110 via interface cable 115 So the scanning module 105 although it has extra hardware operates as a regular scanner as well 4 3 2 Electrical Interface Cable Interface cable 115 is a standard 10 pin cable assembly used to conduct signals from the scanner module 105 to the processor unit 110 and visa versa In one embodiment the cable transmits the following signals digital bar pattern analog VIDEO start of scan edge trigger decode LED laser beam enable power supply and ground The digital bar pattern signal constitutes the digital reflectivity data derived from the scan means The signal ch
38. nerally the appearance of black and gray calibration standards FIGS 7A 7F show exemplary analysis report screens used to report various information derived by a verifier operating in so called AUTO VERIFY mode FIGS 8A D show exemplary analysis report screens used to report various information derived by a verifier operating in so called DECODE DIAGNOSTICS mode FIG 9 shows the orientation of the laser scan beam emitted by the verifier relative to the bar code label of interest in normal operation FIG 10 shows differing possible placements of the veri fier scanning means relative to the label of interest which are illustrative of the need for calibration 4 DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 4 1 Overview of Verifier Operation 10 20 25 30 35 45 50 55 60 65 6 Turning now to FIG 1 a bar code label verifier 100 constituting one illustrative embodiment of the present invention is shown A scanning module 105 is operatively attached to a processor unit 110 via an electrical interface cable 115 A trigger 120 functions to initiate a scan operation by the scanning module 105 Laser light is emitted in a beam from an emitting means located behind a scanning window 125 The scanning window 125 and associated components e g laser emitter components and optical components may be of a design similar to that shown in U S Pat No 4 897 532 Portable Laser Diode Scanning Head by Swartz
39. ng LCD select real time clock keyscan write protection interrupts laser DMA and output latches for some communications and RS 232 signals The gate array also generates the I O select signals for controlling latches and tri state buffers located external to the device In addition the gate array generates the run time system RTS and Custom Application Module CAM EPROM enable signals as well as RAM select signals for the various RAM memory devices 4 3 3 d Communications 5 504 315 13 RS 232 board is provided for communication between the processor unit 110 and host computer The RS 232 board contains the necessary voltage convertors and drivers for true RS 232 level signals An external serial interface device ESID connector is provided to accommodate use of any one of a plurality of existing contact or non contact scanners including the LS 2000 laser scanner that is part of the LaserChek II Symbol Technologies Inc bar code verifier designed according to this invention Data output to this interface is output through a UART located in the 64180 microproces sor Signals are provided which allow the terminal software to determine which peripheral device is attached to the prot and so adjust its response accordingly Data input from the peripheral to the interface is directed to an I O controller and to the UART in the microprocessor Data input from a wand or scanner will be input through the I O controller AS
40. nned by the verifier is classified as a member of a certain symbology e g C39 C93 UPC etc by an application of the following three step method 1 Identify the target label s boundaries by locating its margins 2 Check the number of transitions bar to space or space to bar because certain symbologies can have only certain numbers of transitions and 3 Attempt a character by character decode of the sym bologies passed by step 2 According to another feature of the invention the verifier can be limited in the possible symbologies it recognizes and attempts to analyze That is a user may specify that the verifier is to assume that the target label of interest belongs to a certain symbology or group of symbologies According to another feature of the invention means are provided for analysis of print contrast and quality of bar code labels Software processing of both analog reflectivity data and digital reflectivity data yield a plurality of functions and indices reflecting print contrast and quality respectfully Functions performed and indices produced by the verifier processor using digital and analog data in normal operation include Identification of symbology and data content of label Calculation of label print contrast index Characterization of label print quality rating as measured by bar width growth loss element absolute widths and width ratios Calculation of percent decode index Calculation o
41. o 5 218 190 hereby incorporated by reference for an address map Read only memory ROM in the form of a 64KB run time system RTS erasable programmable read only memory EPROM is used to store the run time terminal operation program A 32KB or 64KB customer replaceable EPROM also known as a custom application module CAM is provided for application programs The verifier application resides in the CAM The run time system EPROM will determine which size CAM is inserted and make appropriate arrange ments The CAM is preferably accessible to the user for example under a battery compartment cover Notably by replacing the CAM with a suitably programmed CAM in the conventional manner the user may operate the verifier as a bar code reader thus getting double duty out of the verifier apparatus The verifier of the present invention uses CMOS static random access memory RAM chips A verifier might be equipped with for example 128KB or 256KB RAM depending on the number of populated RAM chip sites 4 3 3 c Gate Array According to one stated advantage of the present inven tion over the prior art a bar code label verifier according to the present invention is more conveniently portable and less expensive than prior art verifiers In large part these advan tages are related to the use of a custom gate array to handle most of the terminal control functions That custom gate array handles osm of the I O functions includi
42. of spaces and decreasing the com puted reflectance of bars The following table shows a convenient set of adjustment values as explained below Narrowest element size Percentage increase decrease 57 mils 36 8 mils 34 9 mils 32 10 mils 26 11 mils 22 12 mils 19 13 6 The reflectances of the elements read in a bar code label are 5 504 315 19 adjusted in accordance with the width of the narrowest element read For example if the narrowest element scanned is 9 mils the reflectance of the spaces is increased by 32 while the reflectance of the bars is decreased by 32 This compensates for lower amplitude of the analog signal for high density labels due to a larger spot size Above 14 mils in width such a correction may be omitted 5 CONCLUSION The present invention provides means and method for non contact bar code label verification Features new to the art may be combined to produce a verifier able to measure absolute label dimensions at an arbitrary distance and additionally provide instructive new indices about the read ability and print quality of the label as well as discern print contrast Bar code verification information may be stored and or used for a variety of control and analytical functions as recognized in the art The foregoing description of the present invention is illustrative and is not intended to limit the invention to the precise form disclosed What is claimed is 1 A method of
43. ogies not eliminated in step 2 In the first step bar code margins are identified Accord ing to symbologies specifications there is to be a large amount of white space off either side of a bar code label In order to identify these margins and thereby locate the bar code data among the scan data the verifier software looks at transition widths of the binary digitized scan data acquired by the scan operation margin is identified by the software as a wide element adjacent to a narrow element with wide to narrow ratio between them of at least 6 to 1 Having identified both margins the verifier software knows which of the scan data characterize the bar code itself those data between the margins Having properly discerned the bar code margins and thereby the bar code region the software proceeds to eliminate certain possible symbologies by counting the number of binary transitions high to low and low to high in the bar code region Only certain numbers of transitions are allowed for certain symbologies For instance for Code 39 each data character must have ten transitions except for the last one which must have nine Accordingly a bar code label with a number of transitions other than 19 29 39 etc cannot possibly be a Code 39 label Similar restrictions apply to other symbologies Finally a character by character decode attempt is made for each remaining possible symbology in order from high to low security or confid
44. ol being of the type including a pattern of elements having less reflective areas and more reflective areas said method comprising the steps of manually positioning the verifier apparatus including a manually actuatable radiation emitter and a radiation detector at a distance from the location of said target symbol manually directing a radiation beam from said emitter to points on said target symbol by scanning the beam across the target symbol at a variable scan speed receiving radiation reflected from said target symbol to said apparatus processing the received radiation to generate test data representing a parameter related to a measurement of a characteristic of said target symbol providing calibration information to compensate the test data said calibration information including informa tion for compensating for said variable scan speed and processing the test data with said calibration information to provide a measurement of said reflectivity charac teristic 7 The method of claim 6 wherein the calibration infor mation comprises information for compensating for the distance at which the target symbol is positioned 8 The method of claim 6 wherein said step of providing calibration information comprises the steps of placing at least one calibration standard at the location of said target symbol said calibration standard including a pattern of elements having less reflective areas and more Teflective areas direc
45. rbitrary but constant distance from the verifier Means 511i pt o oe ace ota GO6K 7 10 are provided for analog analysis of bar code label contrast 52 U S 235 462 235 437 levels and for derivation of new instructive indices char 58 Fi ld 5 NU MNA M REN 235 462 472 acterizing the readability and print quality Additionally a Hed B 5 463 466 375 432 436 437 438 new method for determination of absolute bar code label 3 64 571 04 552 5 63 dimensions is disclosed The method of calibration for arbitrary scanning distance and angle standardizes not only the verifier s ability to measure absolute dimensions at 56 References Cited unknown distances but also its ability to discern contrast U S PATENT DOCUMENTS under arbitrary lighting conditions and scanning equipment This is accomplished by employing calibration standards of asa abe rue as Pa 364 571 04 known characteristics Bar code verification information 4 360 798 11 1982 Swartz et al 235 463 may be stored and or employed for a variety of control and 4 369 361 1 1983 Swartz et al 235 462 analytical functions as recognized in the art 4 508 686 4 1985 Shaber et al 235 466 4 705 939 11 1987 Ulinski 364 563 9 Claims 10 Drawing Sheets DECODE AUTO REVIEW OPTIONS USER CALIBRATE DIAGNOSTICS VERIFY DATA LD 505 510 515 520 525 530 INDUSTRY gies SYMBOLOGY GROUP CLOCK REPORTS OUTPUT C93 UPC EAN JAN MSI
46. s or spaces and wide to narrow ratio Average width of bars and spaces Number of transitions Size of bar code margins Percent decode Absolute widths of bars and spaces are determined by the application of the calibration conversion factors derived for each bin during the calibration step Transition widths are measured in time not distance as disclosed in Overview of Verifier Operation The temporal relationship between tran sitions is converted to a spatial relationship using the con version scale calculated during calibration Average widths of wide and narrow elements whether _ bars or spaces are calculated from binary digital reflectiv ity data by averaging the absolute widths of transition high to low to high or low to high to low The ratio of the average width of wide elements to that of the narrow elements is calculated The average absolute width of bars and the average absolute width of spaces are calculated from binary digital data A bar is identified as a bar by virtue of its lower reflectivity level Indices corresponding to the average width of bars and the average width of spaces are calculated by applying the calibration generated scale for temporal to spatial conversions The number of transitions high to low or low to high is calculated by counting the number of changes in digital level in the series of data characterizing the digitized reflec tivity levels Bar code margins 215 the re
47. ssible with printed labels The gray bars on the Fay calibration standard 605 represents the lightest bar coloring reliably readable by the verifier sensor Specifically contrast is read from the analog reflectivity data as the difference between the intensity of light reflected by spaces and that of the light reflected by bars So on a contrast scale with levels 1 10 an eight is a high contrast level and a two is a low contrast level Now black and gray calibration standards 600 605 are printed at known contrast levels one with high contrast and one with low contrast as previously shown During calibration a contrast level for each bin on each label is derived Now for each bin there exists a high contrast level index derived from the black calibration standard 600 and a low contrast level index derived from the gray calibration standard 605 Thus a calibration scale relating perceived contrast levels to actual contrast levels is derived for each bin in the measuring sweep The scale can be illustrated graphically by imagining a graph on which the x axis represents perceived reflectivity levels and the y axis represents actual reflectivity levels A line is defined between the two points derived in calibra tion a dark and a light standard Linear interpolation can be used to derive an actual contrast level relative to the known standards for any label for which a perceived contrast level has been found 4 4 2 Software Generated In
48. ta from the digitizer are stored directly into RAM using the direct memory access DMA port on the microprocessor The state machine coordinates data transfer to RAM 4 3 3 f Other To accommodate the lower output voltage of NICAD batteries where used a low resistance HEXFET transistor is used in a voltage regulator circuit The gate voltage of the HEXFET is controlled by a CMOS op amp which compares the regulated voltage to a reference voltage When the power is on the op amp s negative supply becomes a diode drop above 10V When the battery voltage drops below that needed to maintain the desired regulated voltage the output of the op amp will go to its negative rail This will result in the largest IV and therefore the smallest possible voltage drop across the HEXFET The processor unit 110 uses all CMOS technology An eight line by twenty character 64x120 dots graphics Supertwist display is used to provide low power consump tion Printer port 420 consists of a six pin connector and is compatible with for example the PDT III printer port 4 4 Software Setup 5 10 15 20 25 30 35 40 45 50 55 60 65 14 A verifier according to the present invention includes software means for the implementation of a plurality of functions related to calibration to labe identification or to analysis of readability and print quality 4 4 1 Calibration In accordance with the non contact feature of
49. the present invention the orientation of the verifier scanning module 105 relative to the bar code label 200 of interest is assumed to be unknown Part of the software function of the proces sor is to calibrate the measurement scheme of the verifier for a particular scan distance and angle Two challenges are introduced by the non contact feature of the verifier 1 teaching the verifier to measure dis tances widths of bar code elements etc at an arbitrary but constant scanning distance and angle and 2 teaching the verifier how to measure contrast at an arbitrary but constant scanning distance and angle The former problem how to measure distances relates to the fact that the verifier sensor measures reflectivity versus time as opposed to reflectivity versus distance The emitter means produces a scan beam across the bar code label This scan beam 900 is illustrated in FIG 9 in relation to a bar code label 200 being scanned Of course the image of the laser light emitted by the emitter means actually looks like a small dot the continuous beam image 900 is due to the fact that the dot is sweeping side to side at a rapid pace FIG 10 illustrates how placement of a bar code label 200 at an unknown distance from the emitter means of the scanning module 105 will render the verifier unable to discern abso lute widths of bar code elements It will be apparent in view of this disclosure that a certain time te is required
50. ting radiation from said emitter to a plurality of points on said calibration standard receiving radiation reflected from said calibration stan dard processing said received radiation to produce measured characteristics of said calibration standard comparing said measured characteristics of said calibra tion standard to known characteristics of said calibra tion standard generating correction factors based on said comparison using the correction factors to compensate the test data 9 A method of measuring a characteristic of a target symbol which is positioned at a fixed distance from a verifier 5 504 315 21 22 apparatus the target symbol being of the type including a processing the received radiation to generate test data pattern of elements having less reflective areas and more reflective areas said method comprising the steps of er ee ann on i 5 providing calibration information to compensate the test said fixed distance from the location of said target data for said variable scanning speed and symbol scanning a radiation beam from said emitter across said target symbol with the scanning speed varying along jo m said symbol in the scan direction teristic receiving radiation reflected from said target symbol to said apparatus edes representing a parameter related to a measurement of a characteristic of said target symbol processing the test data with said calibration information to provide a meas
51. tivity level transitions detected by scan means These data are placed in random access memory RAM storage by direct memory access DMA operations Immediately thereafter the scanning module 125 acquires another series of data this series corresponding to analog reflectivity levels detected by the 5 504 315 7 scan means during emitting means sweep FIG 3B illustrates this step by step effect of signal processing on the raw reflectivity signal derived from scan means digitizer creates discrete data points corresponding to the analog refiectivity levels perceived by the scan means and further amplified by a differential amplifier The digitizer and the differential amplifier circuitry are disclosed further in the section Hardware Setup It will be appreciated that the series of data labeled Digitized Analog Signal is repre sentative of the reflectivity level detected by scan means Again this series of data is transferred into RAM in the processor unit via DMA operations as disclosed hereinafter With all 29 sets of data in place RAM the scanning operation is complete A processor like a Hitachi HD64180 in the processor unit 110 accesses the data in RAM storage as needed in the software performance of functions and calculation of indices to be specified hereinafter It will be appreciated that the Hitachi HD64180 is also equipped to execute the DMA transfers of scan data into RAM Subsequent processing of the
52. ular scanning module orientation relative to bar code label 200 after the verifier has been calibrated for that orientation As shown in FIGS 4A and 4B the portable processor unit 110 is equipped with a keyboard 405 for receiving user input at appropriate times during verifier operation a central processing unit CPU 406 for performing various control and computation program functions described herein a memory unit 407 accessible to the CPU 406 for storing program instructions and data which of course may com prise DRAMs SRAMs ROMs etc in various combina tions as desired and a monitor 410 for issuing menu choices and decode reports to the user at appropriate times during the verifier operation A host computer port 415 for connecting to a host computer and printer port 420 are available for use in the corresponding output modes In one embodiment the processor unit 110 is battery operated In operation the verifier is menu driven FIG 5 shows the menu structure representing verifier function choices avail able to the user in one embodiment In CALIBRATE mode 5 10 15 20 25 30 35 40 45 50 55 60 65 8 505 the functions to set the maximum minimum contrast limits and adjust the verifier measuring parameters for a given scanning module 105 orientation distance and angle relative to the bar code label 200 of interest AUTO VERIFY mode 515 and DECODE DIAGNOSTICS mode 510 are use
53. urement of said reflectivity charac

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