CA1196085A - Method and apparatus for detecting defects in glass bottles using event proximity - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An inspection device for an apparatus for inspecting objects, such as glass bottles and the like, for defects includes an interface circuit connected between a source of data signals and means for processing information obtained from the object. The interface circuit receives the data signals, typically in digital series form from a photodiode camera and light source, and includes a latch for storing one of the digital signals, a pair of adders, and a storage means for a plurality of threshold signals. Each data signal is compared to the preceding data signal stored in the latch in one of the adders to generate a difference signal representing the difference in magnitudes between the two signals. Each difference signal is compared with a selected one of the stored threshold signals in the other adder to generate an event signal representing the difference in magnitudes between the two signals. The means for processing information includes a pair of control units and a master control means for alternately connecting the control units to the interface means, whereby one of the control units is receiving a group of the event signals representing one object while the other control unit is processing a preceding group of the event signals. Signals are also generated to identify the location of each event signal with respect to a corresponding photodiode and to identify during which vertical sweep of the object the event signal was generated to associate the event signal with a point on the object, The event signals are processed to identifiy defects. Events in proximity in the same sweep are identified as a string. Event magnitudes and totals in a string are compared with predetermined values to identify defects. Strings in proximity are identified as a blob.
Event magnitudes and totals and blob width are compared with predetermined values to identify defects. The event signals can be displayed as a two-dimensional representation of the surface of the object, as if it had been cut and unwrapped.
The operator can repeat the inspection utilizing different threshold values to optimize the defect detection performance of the inspection device. If the storage means is disabled and the threshold signals magnitudes are set at zero, the data signals will pass through to be displayed as the data signal magnitudes on one orthogonal axis and the Location of the associated points on the other axis.

Description

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¦ APPARATUS AND METHOD FOR DETECTING DEFECTS
¦ IN GLASS BOTTI,ES USING EVENT PROXIMITY

.BACKGROUND OF T~IE INVENTION

¦ 1. Field of _he Invention ¦ The present inven~ion relates .in general to sidewall ¦ inspection devices for containers and in particular to ¦ methods and apparatus for adjustiny an inspec-tion device, ¦ for detec-ting defects using event proximity, and for ¦ extracting signi~icant data with respect to defects from a ¦ sparse object, such as a glass bo-ttle.
¦ ~ D _ o~ tbo P~ur ~t ¦ The use of optical scanning devices for inspecting the l sidewalls of containers is well known. Numerous devices, .. . I such as those shown in U.S. Paten-t Nos. 3,708,6~0 and ¦ 3,716,136, have circuitry including means for receiving and ¦ interpreting light passed through or directed onto an item 15 ¦ und~.r inspect;.on. Such devices incorporate either a visua' display or comparison of the item or employ a device capable of producing a~resistance proportional to the intensity of .
light directed thereon. Whether the output of such a device is visual or electrical in nature, it is eventually compared against a model to determine if the item under inspection i5 suitable as to size and construct.ion and is without flaws/
cracks, or foreign ob~ects. Such devices are each intended to provide an automated inspection means for checking, as in . , .. _~.. ~:~.~=~I.~r~_~_~_____ .. ________.__.. ___.. _.. ___.__.. __ _.. ____.. _. _,,__._.. _ _.. ..... _.. _'._ __.. . _.. _ .. :_.. _ ____. _.. _ . . . .. . . _ __ _. __ a movin~ column of bottles, single or multiple o~ects in that moving column.
U.S. Patent No. 3,~77,821 discloses an apparatus having a scanning array that is serially interrogated to generate a train of pulses having amplitudes representing the light transmitted through an object under inspec-tion. Adjacent pulses are compared to generate pul~es having amplitudes which represent the diEference in pulse amplitudes. The difference pulses can be utili.zed to indica-te a defec~ in the object being inspected. U.S. Patent No. 3,942"001 di.scloses an appara-tus for de-tecting the presence of extraneous matter or cracks in translucent containers. A
spot beam of light is projected through the container to generate an inspection signal which is compared with an acceptance signal~ The acceptance signal amplitude i5 varied in accordance with the position of the spot beam with respect to the container.
U.S~ Patent No. 2r798,605 is representative of the prior art inspection circuits and utilizes a cathode ray tube to display the object being inspected. A scanning generator subassembly provides a vertical sweep circuit and a horizontal sweep circuit for the scanning element of a cathode ray presentation tube pro~ided in a monitor unit.
An iconoscope is provided for receiving a focused image of the bottle under inspection. The monitor is arranged to receive the ~video output of a selected camera unit and is controlled i:n its electrostatic deflection circuits by the same sweep vol'ca~e waves employed in the deflection circuits

-2-.. ~ ' ' .. .' ~ I ., . . _ . of the selec-ted Gamera unit, so -that it reproduces -the pic-ture image focused on the iconoscope~

The present invention concerns a method and apparatus for performing the setup of an inspection device for objects such as glass bottles ~nd for displaying an output of the inspection device. ~ di~itized video siynal representing a point oE inspection is ge~erated by a photodiode camera.
The digi-tized video si~Jnal is generated to an adder and to a latch in which is s-tored the digitized video signal from the . previous point of inspection. ~ signal representing the difference be~ween the present digitized signal from the adder and the previous digitized signal from the latch is generated and comparecl with a stored -threshold level for the current point of inspection. If the threshold level is exceeded, the difEerence signal is s-tored as an event signal.
When the entire bottle has been scanned, the stored . inEormation may be generated to a means Eor displaying the stored signals on a video screen. The signals are displayed in a two-dimensional representa-tion of the surface of the inspected object, as if the object had been cu-t through one side and unwrapped for display. The stored signals include . the location of each detected defect, thus enabliny the clisplay means to prope.rly pos.ition the de:Eect on the video screen relative to -the representation o:E the unwrapped object. By u-tilizi.ng the apparatus in this manner and Vary.incJ the tllreshold levels, the operator can determine .' ' ' ,.

what the proper threshold leve]s should be ~or inspecting the particular object.
The apparatus can also be utilized to monitor the ou-tput of the inspection device. The latch is disabled, the threshold signal is cleared to zero, and only one vertical inspec-tion sweep is made of the object. The data is then -transferred to a means for displaying the signals as a two-dimensional represen~ation of the signal magni-tude on one axis and the loca-tion of the point on the othex axis.
10~ By utilizing the apparakus in this manner, the operator can adjust the sensitivity of the inspectiorl device to the camera signals without using an oscilloscope or o-ther external device.
In a further embodiment, -the present inven-tion also con-cerns an apparatus for extracting on~y the significant data from an optical inspection of a sparse objec-t, such as a glass bottle.
A digitized video signal representing a point of inspection is generated by a camera and associated light source to an interface circuit including an adder and a latch in which is stored the digitized video signal from the previous point of inspection. A signal represen-ting the difEerence between the presen-t digitized signal and the store~d digitized signal from the latch is generated by the adcler and compared with a stored threshold level for the currerlt point of inspection.
IE the threshold level is exceeded, an event signal is generatecl and stored in the interface circui-t.
AEter the object has been scanned, the group of event sicJJlals is processed -to determine iE a deEect is present.

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mas-ter control uni,t means al-ternately connects a pair of control units to the interface, where~y one of the control units is reeeiving a group o~ event signals while the other control unit is processing a precediny group of event signals.
In ye-t ano-ther embodiment, -the present invention further concerns an apparatus and method for extracting data from a scan of a slasscontainer and utilizincJ the extracted data to de-termine the physical size and in-tensi-ty of localized defects to ascertain the acceptabili-ty of the container. A pho-todiode array and light source are utili7.ed to generate signals representing the amount o~ light received from points on the container.
Event signals are genera-ted when the magnitudes oE adjacen-t diode signals are clifEerent by an amount which e~ceeds a threshold level. The even-t signal magnitude and posi-tion are stored .in an inspection device interface and transferred to ei-ther a firs-t or second control unit, both of which are responsive to the event signals for determining whether to generate a rejec-t signal.
~ master control means alterna-tively connects one of the first and Isecond control units -to the interface, whereby the connected control unit receives the event signals from the interface wh.ile the other contro:l unit determines wh~ther to cJenerate a rejec-t signal by processing the event signals of a preceding bottle. In making this deter~ination, each even-t along a ver-tical sweep is checked to see if .it ca.n be linked to a preceding event by not exceecling a user-specified separation be-tween the associated .. ~5- ..

poin-ts on the container. A string is formed when -two or more events are in proximi-ty to each o-ther. The app~ratus checks for excess string magnitude as one basis for bottle rejection. If a bottle is not rejec-ted on a string, the strings are checked to see if they Eorm a blob. A blob is a plurality of strings in proximity -to each o-ther. If -there is no blob rejection, a final check is made -to see if the number of events forming the blob is sufficien-t to exceed a small defect threshold.
According to the present inven-tion, then, there is provided an inspection device in an apparatus for detect-ing defects in successive objects and for providing a plural-ity of pixel signals each representing the magnitude of light received from a corresponding point on an object, the in-spection device comprising an interface means responsive to the pixel signals for comparing successive adjacent pixel signals and generating an event signal when the comparison indicates the presence of a defect, the in-terface means storing a readable group of characteristic signals representing the total number of event signals generated by a corresponding objec-t, each characteristi.c signal including a firs-t signal indicating the magni-tude of a corresponding even-t signal and a second signal indica-ting the loca-t:ion oE the point on the objec-t from which the event signal is generated; and first and second control means respecti.vely responsive to successlve groups of charac-teris-tic signals corresponding -to successive objects for processing the characteristic sig-nals and providlng a reject signal to discard the corresponding object when one of the firs-t and second control means indica-tes that a rejectable defect is presen-t.

According to a fux-ther aspect of the present invention, there is also provided a method for detecting defects in an object being inspec-ted by an apparatus providing a plural-ity of pi~el siynals each represent:ing the magnitude of ligh-t received from a corresponding point an an object, comprising the steps of (a) generating an event signal when the absolute value of the difference between the magnitudes of adjacent pixel signals exceeds a predetermined -threshold value associ-ated with the location of a corresponding poin-t on the object indicati.ng the presence of a defect at that point; (b) storing a readable group of characteristic signals, representing the total number of event signals generated by a corresponding object, each characteristic signal including a first signal indicating the magnitude of a corresponding event signal and a second signal indicating the location of the point on the object from which the event signal is generated; (c) processing a group of characteristic signals to identify the presence of a defect in a corresponding object; and (d) providing a reject signal to discard the object when a reject-able defect is identified.
Embodiments of the present invention will now be describedin greater detail and will be better ~mderstood when read in conjunction with the following drawings in which:
Figure l is a block diagram of an apparatus for detec-ting de:Eects in objects according to the present inven-tion; and Figure 2 is a block diagram of the inspection device interface o:E the apparatus :Eor detecting de:Eects of Figure 1.
ReEerring now to the drawings, there is illus-trated in Figure 1 a block diagram of an apparatus for detecting defects in objects according -to the present invention. ~n object, such -6a-...~

as a glass bottle Inot shown), is scanned by a camera 10.
The camera 10 generates a plurality of signals proportional in magni-tude to the amount of light received from the glass bottle. In the preferred embodiment of the invention, a light source (not shown) directs a beam of light through the glass bottle under inspection and into the camera 10.
The camera 10 includes a plurality of photosensitive devices, such as photodiodes, which are vertically arranged in a linear array. It has been found that a linear array of two hundred fifty-six photodiodes yields satisfac-tory resul-ts.

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¦The photodiode is a variable reslstance device that will pass a voltage proportional to the amount of ligh-t fclllinc3 thereon~
~ach photodiode receives light which has passed through different !se~ments or ~or-tions oE the bo-ttle under inspection. If a flaw, ¦crack, or foreign ohject i5 contained in the bottle, then the ~light passing through that por-tion of the bottle will be partially !blocked or reElected and the corresponding photodiode will regi-¦s-ter a lesser intensity of light than had no deEect been present.
¦ The signals Erom -the photodiodes of the camera 10 are suppli-led to a sampler 14 on a p]urality of lines 12. Each of the ~photodiodes is sampled in sequential order, producing a series of pixel signals on a line 16 which represent the amount oE light which passed through the bottle under inspection along one ver-ti-Ical sequen-tial sweep oE the pho-todiodes. ~he sampler 14 is a ¦device ~ell known in the art. By rotating the bottle ~nder inspection relative to the camera 10, a plurality of different sweeps can be made, each sweep inspecting a diE~erent portion of ¦the bottle. It has been found that about three hundred seventy-¦fi~e to four hundred sweeps will suE~iciently cover an average ~0 ¦bo-ttle and ensure an accura-te inspection. Thus, the sampler 1 generates a plurality of series oE pixel si~nals on line 16 representing the amount oE light passiny through the inspected portions of the en~ire bot-tle.
I The pixel si~nals from the sampler 14 on line 16 are an ¦input to an inspection device interEace 18. The interface 18 ¦rapidly extxacts si~n:ific~lnt data Erom a sparse objeck, such as a ¦~lass bott:Le, in a mannex suitable Eor computer analysis. When a bottle :is reacl~ to be scanned, the interFace 1~ i5 enabled to ~receive and store data concernin~ tha-t bottle. I~hen no bottle is ready to be scanned~ the interEace :L~ stor~s the data concerning . .

3~ 1 the last scanned bot-tle ~ntil a new bottle is ready to he scanned.
The operation o-E the int~rface 1~ is more full~ explained below.
The interface 1~ is ~ means for yenera-tiny groups of siynals ¦
Irepresenting the charac-teristics o~ the bottle u~der inspection.
IThe output of the interface 18 is ed to a control circuit for ¦generatincJ a reject signal whenever a defective bo-ttle is detect-ed. The control circuit includes a first control un}t means 20 and a second control unit means 22, which receive the output Isignals from the interEace 18 over lines 24 and 26 respectivel~.
IThe first control unit 20 and the second control unit 22 are each ¦responsive to the groups of signals representing the charac-teris-tics of the bottles under inspec-tion or determining whether to generate a re~ect signal.
I The ~irst control unit 20 and the second ccn~rol unit 22 are ¦
jconnec-ted to a master control uni-t means or processor 28 b~ lines 30 and 32 respec-tively. The master processor ~8 also provides inputs to the interface 18 over a plurality of lines 34 to allow an operator to set certain tolerance limits, as will be more ~ully Idescribed below. The master processor 28 alternately connects lone of the first and second control units 20 and 22 to the inter- ¦
Iface 18 to receive yroups of signals representing the ch~racteris-tics o a bottle while the other of the first and second control units 20 and 22 determines whether to generate a reject signal based upon the plurality oE signals representing the characteris-tics o~ a precediny bottle. ~hus, while the Eirst control unit 20 .~s readiny da-ta ~rom the inspection interface 18 concerning a bottle which has just been scannedl the second control unit 22 is ¦
processing data obtained on a priox scan to determine whether to qene~ate a ej~ct s ~ndl 'or the preceding bottle.

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The master processor 2~, the first control unit 20, and -the t second control uni-~ 22 can all be micxoprocessors, such as a ¦ model. 6B00 manufactured by ~o~orola which is conventional and well known in the art~ The ma~ter processor 28 has an i.nput device 36 by which an op~rator can program the s~s-tem and set ~arious tolexance parameters, The input device 36 i5 connected to the master processor 28 by a line 38. ~he master processor 28 is also connec-ted by a line 40 to an output device 42, such as a video displa~, so as to permit an operator to monitor or calibrate the system. Alternatively, the device 42 can be a means xespon-.
sive to a reject signal generated by the master processor 28 ~or .
rejecting a particular bottle which has been determined to be ¦ defective. A fur-ther input to the master processor 28 is a gauge ¦ 44, The gauye 44 is provided to generate a signal on.a line 46 ¦ when a bottle is in the proper position to be scanned, The interface 18 can receive data so long as the gauge 4~
¦ signals that a bottle is in the proper scannin~ position. When. .
the gauge 44 ceases to senerate such a s1ynal, as during the . ¦ period when the inspected bottle is removed and an uninspected I bottle is moved in, the collected information is stoxed in the .inter~ace 18. The master processor 2~ prevents intexferellce between the irst and second control units 20 and 22 b~ selecting one of the units to receive the data held in the interface 18~ .
When all of the data has been transferred to the first control .
unit 20, fox example, the interface 18 is free to receive new . data on the next bottle as soon as the signal fxom the gauge is restored. The ~irst control unit 20 processes the data in . orde.r to determine whether to generate a reject signal, ~hen scanning :is completed on the next bottle and the gau~e ~4 ceases ~ to generat its si~nal, the accum~lated Cid ta i5 sto~ed in the '. ' '.' ' ',_ ~
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interE~ce 18. Tlle Tnaster proceSsor 28 the~- sel.ects the second con-trol un:it 22 to receive the ciai a while the first Gon-trol unit . 20 continues to process tihe origin~ll inorm~-tion. Thus, each o~ ¦
the control units 20 and 22 has -iwo full c~cles of -ihe gauge 44 to process the dat~ concerning each bo-ttle to det~rmine whe-ther ¦or not to generai`e a reject signal. By providing parallel pro-¦cessing paths, the control circuit increases the speed and ef~-ciency of the inspec-tion apparatus. .
Referring now to Figure 2, there is illustrated a block Idiagram of the details of the inspection device interface 18.
The interface 18 is a means for rapidly extrac-ting si~nificant !data from a sparse object, such as a glass bottle, in a manner isuitable for computer analysis. The samp]er 14 can generate digi- .
!tal si~nals, or analog signals to an analog-to-digital converter, representing the magnitude of the light receivecl by the camera .
lO. Line 16 presents the plurality of signals to an event ~detector 48 including a data latch 50 and an adder 52~ The latch lis a means for storin~ one o the plur~lity of signals. In the ¦illustrated em~odiment, the preceding pixel signal is stored in !the latch 50 and is presented to the complementary input of adder 52. Thus, the adder 52 is a means for generating a signal which ¦represents the diffe.rence between the ma~nitude of the stored preceding pixel signal in the latch 50 and the successive pixel ~ signal presen-ted on line 16. The output of the adder 52 is a signal representing the difference in the magnitudes of adjacent . pixel signals. When the difference signal is generated by adder . 52, the present pixel sign~l is stored in latch 50 to be compared with the next pixel signal. ~ con-trol logic unit 54 of the interface 18 generates a command over a L~TC~I NEXT PIXEL line to cau~,e th- latch 50 to 9 toxe tbe present pixel signal available on . . ~ ~

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¦line 16. rrhe con-tents of ~1le latch 50 c~n be cle~red to zero by a command from the m~ster processor 28 over a CI,EAR IJ line.
The dif~erence signal from ~he adder 52 c~n be either posi-1 tive or ne~a-tive, dependincJ upon ~he magnltudes of the present 1land previous pixel signals. Because only the mayni-tude of the ¦¦difference between adjacent pixel signals is relevant in the de-tection of defec-ts, it is convenien~ to feed the difference 1 signal to a means for generating the absolute magnitude of the ¦¦diEference siynal. As illustrated, the output fxom adder 5~ is 11 fed to an absolute ma~nitude circuit 56. The circuit 56 can be ~¦ con~tructed of a plurality of exclusive OR gates, as is well ¦known in the art. The C~RRY output of adder 52 controls the -¦
1 absolute magnitude circuit 56 such that the output is always ¦ positive. Rectificatio1l o~ the difference signal prevents mis- ¦
15 I leading com?arison readin~s in the even~ detector 48.
I The event detector 48 includes a means for storing a thres-¦ hold siynal. In the preferred embodiment, a threshold random j access mernory (RAM) 58 is provided ox s-toring a plurality of 1 threshold signals. Each -threshold signal stored in the threshold ¦ R~M 58 corresponds to a specific pixel difference signal generated b~; the adder 52. The means for selecting the individual threshold signal from the threshold R~M 58 which corresponds to the pxesent difference signal is a diode counter 60. The diode coun-~er 60 1 can be cleared to zero by a command from the control logic 54 over a CLEAR DC line and can be incremented by a command over an INCREMENT DC line. The diode counter 60 provides the threshold ~M 58 with the memory addre~ss of the proper threshold signal~ ¦
The desired threshold signals can be loaded into the threshold I RAM 5~ from the mast~r processor 28 o~er ~ LOA~ DAT~ line. The 30 ~ output f the diode counter 60 is al50 conneoted to an internal !
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i ,' data bus 62.
The sictrlal from the threshold ~M 58 is prese~ted to the Icomplementary inpu-t of an aader 6~ where i-t is combinecl with ~he ¦signal from the absolute magnitucle circuit 56~ The adder 64 is a !
¦means for generating cven-t signals when the difference signal ob~ained from the absolute magnitude circuit 56 differs from the Ithreshold signal obtained from the threshold R~ 58. Even~
¦signals are generated, over an EVE~T line to the con~rol logic ¦54, indicating the detection of a defec~ and over a MAGNITUDE
¦line to the internal data bus 62, inaicating by how mu~h the ¦difference signal difEered from the threshold signal ~ Upon receiving a signal ~rom the ~auge 44 that a bottle is ¦ready to be scanned, the mastex processor 28 generates a signal ¦over a GAUGE line to the control logic 54. In response to that ¦ signal, the control logic 54 generates a signal over a CLEAR SC
line to ~ sweep counter 66. The contents of the sweep counter 66 ¦
I are tnus cleared to zero before each bottle is scanne~. The ¦ output of the sweep counter 66 is connected to the internal data ¦ bus 62.
20 ¦ T~ initiate a sw~ep, the master procescor 28 genera~es a signal over a START SWEEP line to the control logic 54. In response to that signal, the control logic 54 increments the sweep counter 66 by generating a signal over an INCR~UENT SC
line. The control logic 54 also clears the contents of the diode counter by yenerating a signal over the CLEAR DC line~ The control logic 54 further generates a sicJnal over a C1E~R EC line to clear an event counter 68. These three initialization func-tion~ prepare the inter~ace 18 ~or the receipt o~ d~ta. The output oE the event counter 68 is connected to the internal data 30 ¦ bu6 6Z. T evFnt ooun`-r 68 generat~s a si~nal ~n an OVERFLOII

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' . ' ' -l~_ line to the data bus 62 ~hen -the con-tents oE the register excee~d its limits. The even-t count~r 68 is incremented by the control . jlo~ic 5~ over an INCREMI.~N~r EC line each time that -the event ~¦de-tector ~8 signals ~hat an event has occurred.
¦ The in-terface 18 includes a means for storing the even-t ¦¦signals. An interface random access memory ~R~) 70 is provided for reading and s~oriny the signals available on the data bus 5~. 1 I! The first con~rol unit 20 and the second control.unit ~2 alterna- ¦
- l¦tively read the accumulated data from the interface RAM 70 ¦I through the data bus 6~ and lines 24 and 26 respectively. Da-ta ¦¦is stored in the inte:rface RP~I 70 when the control logic 54 generates a signal over a W~ITE line. The interace RA~ 70 also generates a signal OII an OVERFLOI~ line to the data bus 62 when the contents of the recgister exceed its limits. A RAM counter 72 ¦I provides the interface ~M 70 with memor~ address locations. The RU~I counter 72 can be cleared to zexo by a command from the ¦ control. lo~ic 5~ over a CLEAR RC line and can be incremented by ¦ the control logic 54 by a command over an INCREMENT RC line..
¦ The interface 18 also includes a means for deEining a range .

¦ for extracting data. In the illustrated embodiment, a window generator 74 is provided to limit the number of sweeps over which data can be extracted. A lower sweep limit is entered by an operator through the input device 36 to the master pxocessor 28.
. The instruction is sent over a LO SET line to a low sweep com-parator 76. ~he output of the sweep counter 66 is also an inputto the low sweep comparator 76. When -the number in the sweep counter 66 e~uals or exceeds th~ number ge.nerated over the hO SET ¦
line, the low sweep comparator 76 generates a signal over a SET
line to a :El:ip~flop 78. The flip-flop 78 generates a signal over ¦
an EN~BLE lille to the con:rol logic 54, i.n.tructing it to process ~

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61.`~35 the inCOminCJ data. Si~nals received by the i~terface 18 on sweeps taken of a bottle be~ow the lot~er s~eep limit are ignored ¦
¦ to preVent erroneous data assoc;ated with the initial sweeps from ¦ bein~ processed. Similarl~, ~he operator can enter a high sweep ¦ limit value to cause the interface 18 to stop processing data aEter a certain number of sweeps. The mast2r processor 28 sends the instruction over a H:~ SET line to ~ high sweep comparato~ 80.
The output of the sweep coun-ter 66 is also an input to -~he high il sweep comparator 80. When the number in the sweep counter 66 ¦¦ equals or exceeds the number generated over the III SET line,-the ¦ high sweep comparator ~0 generates a signal over a RESET line to ¦ the flip-~lop 78. The flip-flop 78 thus ceases to generate the ~ signal over the ENABL~ line, causing the control logic 5~ to i~ ignore all subsequen-t data.
1~ Prior ~o utillzincJ the apparatus for detectinc~ deec-ts, the operator will enter the parameters ~nder which the machine wiLl ¦ operate throu~h the input device 36. The parameters include the I low and high sweep limits and the group of threshold signals. - ¦
i ~he low and high sweep limits define the sweep window, which is 2~ ~the ranye of sweeps over ~hich data can be accep,ed hy tlle inter- !
i face 18. B~ selecting a par-ticular set of threshold sicJnals to be loaded into,the threshold R~M 58~ the operator determines the acceptable tolerances of ligh-t devia-tion which will cause an e~en-t to be detected. The master processor 28 loads the appropri-ate data into the inter~ace 1~.
When a bottle has been movea into a proper position EorscannincJ, the cgaUcJe 4~ cJenerates a siynal to the master processor . Th~ signal is relayed alon~ the GAUGE line to the control log:ic 5~, which generates si~nals to clear the contents of both the sweep c ~nter ~- ard the R~M .o~, Le~ 72. ~rhese tasks a~

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....... : ... . . ,.. .... _.. :.. . .. ..... i ~perEormed each time c-l ne~ ~ottLe is ready-to be inspected. The 'in-terface 1~ is thell prepar~d to receive data from the camera 10.
j At the beyinning of e~cll sweep, the master processor 28 !yenerates a signal over the START SI~P line to the control logic I
i54. The control logic 5~ ~enerates appropriate signals to clea~ .
~the contents of the diode counter 60, clear the contents of the event counter 6~, and incremen-t the conten-ts o~ the sweep counter 166. These tasks are performed a~ the beginning of ea~h sweep , ¦Imade by the sampler 14, ', I The incoming pixe:L signals are fed to the adder 52 and ~he ¦llatch 50. The latch 5~ holds the previous pixel signal a~ iks ~outpu-t, s7hich is then f~d to the complementary input of the adder 1,52. Tnus, the outpu~ oE the adder 52 represen-ts the difference bet~Jeen tne two adjacen-t pixel signals~ The output of the adder 15 ¦¦ 52 is fed to the absolute magnitude circui-t 56, which insures !I that the input to adder 6~ is always a positive signal.
The threshold RA~I 58 holds the prograr~ned plurality oE
threshold s.ignals, each of which corresponds to a specific differ-¦
ence signal representing a pair of pixels. Since each pixel ~0 ¦ signal reprcsen-ts a sampled photodiode ~n the camer~ 10, the , diode counter 60 can be incremented with each incoming pixel signal to sele~ct the memory address of the appropriate threshold signal stored in the threshold RAM 58. That particular threshold signal is fed to the complementary input of adder 64 to be com- ' ¦ pared with the actual difference signal yenerated by adder 52 and .
rectiEied by the absolute ma~nitude circuit 56. The output oE
adder 64 is a pl.uralit~ of even-t si~nals which represent a com-parison between the dif:Eerence siynal and the threshold si~nal.
When the magnitude of the difEerence signal exceeds a predeter-30 ¦I mi-ed amoun , the aclder 64 wi] L ~-nerate an event siynal ove~ tbe l `' : - . , . l '',~,.,~ . , .' ' '. I
.' : . -lS.--: '' '.
- - -~ 5 IEVENT line to the control locJiC 5~. The ma~nitude of the event jsi~nal as well as the outpu-~ of the diode counter are ga-ted onto ¦the dat~ bus 62 for s~ora~e in the interface ~1 70.
¦ When an event is de~ected during -the s~.~7eep window, as defined ~by the oper~tor usincJ the window generator 74, the control l~gic 54 genera-tes signals which increment the event counter 68 a~d increment the R~M coun~er 72. The con~rol logic 54 also generatesl I . - . I
a signal over the WRITE line to the interface RAM 70 to read and ~store the contents of the diode counter 60 and the magnitude of Itlle output adder 64, 'I'his process is repeated with each pair o adjacent pixel signals until a sweep is completed. The signal on the START SWEEP line is removed at the end of each sweep, causing ¦
¦the contents of the sweep counter 66 and the event counter 68 to ~be wri~ten into the inter-~ace RAM 70 if one or more events have occurred in that par-ticular sweep. Thus, in each sweep where an I! event is detected, the ga-thered data includes a series of events denoted by diode nurnber and event macJni-tude, followed by a final Isingle entry consisting of the sweep number and the number of ¦events which occurred in that sweep. When -the next sweep of the -jsame bottle begins, the con-tents of the diode counter 60 are ¦cleared -to zero, :the contents o~ -the event coun-ter 68 are cleared ¦to zero, and the sweep counter 66 is again incremen-~ed. The I Iscanning con~inues ~mtil the window ~enerator 74 disables the ¦inter~ace 18 when the hi~h sweep limit has been reached.
The groups o~ ~ignals stoxed in the interEace ~M 70 which represent the characteristics o~ the'inspected bottle are then ~ed to either the first control unit 20 or the second control unit 22, as determined by the master processor 28. 'The data in the interEace RAM 70 :is downloaded into the selec-ted con-trol unit~ which determines whe-the or not to ~enerate a reject siqnal . , I
.. . . ' "' '.1 :' ' ' -16-.. .. .. . . .

s ¦Ifor that parl:icul~r ho~-tlc~ T~o checks are m~de before process-¦ illCJ begins to make sure tha~ the inte~ace 1~ has not overflot~ed ¦because oE an unusually b~d bottle. These checks are in~i,cated by stat~ls flags on the event counter 68 and the interEace ~ 70. !
If the contents o~ ei~ller unit exceeds -the capabili~y of the ¦xegister, a signa:L is gerlerated over the respective OVERFLOW
lines. When either overflow signal is present~ -the bottle wili be immediately rejected because of a gross deEec-t.
As stated above, ~he format of the data which is read by,the n ¦ selec-ted control unit includes a series of diode numbers and associated event magn.i-tudes, followed by a s~eep nu~lber and a ¦ number of even-ts. The bottle da-ta is downloaded from the inter- ¦
i face RA~1 70 to the' particular control uni.t. By checking each i event along a sweep to see if i-t can be linked to a prec~ding ! event, the control units 20 or 22 can generate a string.
string i5 defined as a collection oE one or more events in prox- ¦
imity,to each other and having four proper-ties which are calcu-la-ted during generation. These properties include: the beginning ' ! of -th~ string, which is the firs~ diode,number; the end of the '20 ¦ strlng, which is the last diode number; the magni-tude of each string, which is the sum oE the magni-tudes oE each even-t compris-'~
ing the string; and the number oE even-ts that formed ~he string.
Checking for excess str.ing magnitude occurs during string genera-tion and the decision process will halt if a stri.ng magni~ude exceeds a user-adjustable threshold. In o-ther words, the select-ed control un.it 20 or 22 links -together events within a single sweep to determine i:E the sum o~ khe ma~nitudes oE the events exceeds ~ user-specified tolerance. IE so, a reject signal is cJenerat ~. r nd th partic: rlar bottl~ will b~ r~rno~ed ! :
Il .
~ 1.7-IE strin~ checkillcJ does n~t rej~ct -Ihe bottle, ~notl~er proCessincJ s-taye is entered wherein the strings a~e checked to ,see if ~hey Eorm blobs A blob is definecl as a collection of ~s-tri.ngs in proximity -~o each o-ther. The s-tring diode numbers must overlap~ or a-t most be within a usex-specified range, for the end of one s-triny on one sweep and the beg.inning of ano-ther string on a different sweep. A blob has three properties which are calculate~ during formation. r~hese pxoperties include blob ~width, blob magnitude, and -the number of events in the blob.

IDuring blob formation blob wid-th and blob magnitude are checked lagainst user-specified tolerances and processing s-tops if either ¦-threshold is exceeded. I~ a bottle is not rejec-ted because of ¦blob width or blob magtlitude, the number of even-ts contained in ¦the blob is compared to ano-ther user-specified number. If the ~jnumber ol events exceeds the specified tolerance~ the bot-tle will ¦
¦also be rejected. If the bottle has not been rejec-ted ~or any o~
¦the above reasons, it is considered a good bottle and no re~ect ¦signal will be generated.
The apparatus for de-tecting defects can also be utilized ko 2~ generate and display a picture of the object under inspection.
A bottle is inspected under the normal procedure described above an~ data is stored in the interface RAM 70. When the bottle ¦ has been completel~ scanned, the mas-ter processor 28 instructs ~ither the first con-trol unit 20 or thc-~ second control unit 22 to recei~e the data from the .inspection interEace 18. The selected control un:it 20 or 22 does not process the received informatio~
but rather transmits the data in raw form to the master processor 28. The cJathered data inclwdes the diode nur~ber, the sweep number, ra~d the event magn:itude Eor each event de-tected by -the .intcrface 18. rl'he data is then presen-ted to the output device .' ., , .' . '-.', I . ' ' , ¦l ~2, t~hich can inclu~ a t~o-dimensional graphic moclule and a ¦video screen. I~he graphic module and video screen a~e well kno~n I
in the ar-t. The d~ta c~n b~ displayed in a two-dimensional 1.
graphic form, utilizincJ the sweep number of each evenk as the .horizontal component and the diode number o~ each event as the- I
vertica~ component. The video screen will display a do-t at each ¦
sweep and diode number loca~ion where an event was detected. The result is a two-dirnensional repres.entation of the inspected ~ bottle showing all o the detected de~ects, as i~ the bottle had ¦

¦¦ been cut throu~h one side and unwrapped for display. The event ¦l magnituae may be used :i.n conjunc-tion wi-th z synthet.ic threshold ¦ level which can be vari.ed to generate new pictures which show the ~ e~fect that different threshold levels have. Using t~e apparatus ¦ in this mode, an operalor is aided in de-termining what the appro- .
priate ~hreshold levels fox the par-ticular style of bo~tle should be. Although the preferred embodiment of the invention pxovides only a two-dimensional representation of the objec-t ~nder inspec-... tion, it ~ill be apprecia-ted that a three-.dimensional representa-~
j tion could be ~enerated on the video screen by the use of addi-2~ ~j tional circuitry. Such circuitry is also well kno~n in the art. I
The apparatus -Eor detecting de~ects can also be utili~zed to ¦
. monitor the ~ideo output of the line scan camera. Such a use . . . permits an ope~rator to calibrate the interface 18 without requir- !
. ing the use o~ an oscllloscope. When the apparatus is operated 2$ in this mode, the master processor 28 continuously clears the conten-ts of the latch 50 to zero by ~enera-ting a signal over the ¦
CI.~ L line. With the latch 50 clearea, ~he plurality oE pix~l si~Jnals on lines 16 frorn the sampler 14 pass through the adder 52 unalter~d. The master processor 28 also utilizes the LO~D DATA

3U ~ ¦ l:ine to I ad Lhe Lhreohold R~M 5~ with al- zeros. Thus, every .~ . ' - . ' "~ , .: : ' ' ' .
''' I . ,,, -19-., , . 1.

I pixel si~nal i.s deti~cte~cl as an ~ven-t and is s-tored in thi~ inter-face RA~I 70. Since the in-i~erface R~l 70 is limited in size, only one sweep of the bottle is taken -to prevent memory overflow. The 1, master processor 28 selects either the first control unit 20 or 5 il the second control unit 22 to receive the data Erom the interface R~70.

Each event can be stored in the second control unit 22 . to receive the data from --he interEace RAM 70. The data .. includes the diode number and event magnitude for each J.0 1 pixel of the sweep. The data is transferred from the i selected control unit 20 or 22 to the master processor 28.
i~ The master processor ~8 relays the information to the output device 42, wnich again can consist of a two-dimensional ,. graphic nodule and a video screen. The graphic module can 1.5 1 utilize ihe diode number as the horizontal component and the l event magnitude as the vertical component. The graph which ,~ is thus displayed on the video screen represents the amount j, of light xe~eived by the photodiodes over a single sweep. I
¦I The procedure can be repeated continuously to slmulate an t ¦, oscilloscope. However, unlike an oscilloscope, no sweep or i ¦I gain adjustments are necessary since the data is always i Il properly scaled to a specific diode number or event ¦¦ magnitude. Operation of the apparatus in this mode permits .
¦l an operator tb make sensitiv.ity adjustments relating to the ¦! event magnitude voltage without requiring the use of an j Il oscilloscope . .¦
'I
In accordance with the provisions of the patent ~! statutcst the pr.inciple and mode of operation of the 1~ invention have been explained and il].ustrated in its 1¦ pre:Eerred embodiment. Mowever, it must be understood that Il the inventiorL may be practiced otherwise than as 1~ spe~ciiccLlly illustrated and described withou-t departing .

Il from its spirit or scope. 1, i 11 ,.

Claims (72)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An inspection device in an apparatus for detect-ing defects in successive objects and for providing a plurality of pixel signals each representing the magnitude of light received from a corresponding point on an object, said in-spection device comprising:
an interface means responsive to the pixel signals for comparing successive adjacent pixel signals and generating an event signal when said comparison indicates the presence of a defect, said interface means storing a readable group of characteristic signals representing the total number of event signals generated by a corresponding object, each characteristic signal including a first signal indicating the magnitude of a corresponding event signal and a second signal indicating the location of the point on the object from which the event signal is generated; and first and second control means respectively respon-sive to successive groups of characteristic signals corres-ponding to successive objects for processing said character-istic signals and providing a reject signal to discard the corresponding object when one of said first and second control means indicates that a rejectable defect is present.

2. The inspection device of claim 1 wherein said interface means include data storage means for storing suc-cessive ones of said pixel signals; difference signal means connected to said data storage means for generating for each one of the pixel signals a difference signal representing the difference in magnitudes between one pixel signal and a preceding one of the pixel signals; threshold storage means for storing a plurality of threshold signals; comparison means connected to said threshold storage means and to said difference signal means for comparing each of said difference signals with an associated one of said stored threshold sig-nals and generating said event signal when said difference signal magnitude differs from said associated threshold sig-nal magnitude by a predetermined amount; and event storage means connected to said comparison means for storing said event signals.

3. The inspection device of claim 2 further in-cluding absolute magnitude means for generating said difference signal as the absolute magnitude of the difference between said one and said preceding one of the pixel signals.

4. The inspection device of claim 3 wherein said data storage means includes a latch for storing said preceding one of said pixel signals.

5. The inspection device of claim 4 wherein said difference signal means includes an adder having one input connected to the source of said pixel signals and a comple-mentary input connected to an output of said data storage means for generating said difference signal.

6. The inspection device of claim 5 wherein said threshold storage means includes a random access memory.

7. The inspection device of claim 6 including selection means connected to said threshold storage means for selecting said associated one of said stored threshold signals for comparison to respective ones of each of said difference signals.

8. The inspection device of claim 7 wherein said comparison means includes an adder having one input connected to an output of said difference signal means via said absolute magnitude means and a complementary input connected to an output of said threshold storage means for generating said event signal.

9. The inspection device of claim 8 wherein said event storage means includes a random access memory.

10. The inspection device of claim 9 further in-cluding event display means connected to said interface means for displaying said event signals as the output of the in-spection device in a two-dimensional visual representation of the surface of the inspected object.

11. The inspection device of claim 8 wherein said pixel signals are provided by a photodiode array, each photo-diode generating one of said pixel signals; and wherein said interface means is connected to said photodiode array and compares successive pixel signals from adjacent ones of the photodiodes to generate each one of said event signals.

12. The inspection device of claim 11 wherein said event storage means includes a random access memory.

13. The inspection device of claim 12 wherein said comparison means further generate said first signals represent-ing the magnitude of the difference between each of said difference signals and the associated one of said threshold signals, said first signals being stored in the random access memory of said event storage means, and wherein each of said first and second control means include processing means for summing said first signals and comparing the sum obtained thereby with a predetermined value to detect a defect in said object.

14. The inspection device of claim 13 wherein said processing means includes means for counting the number of said event signals generated and comparing the count with a predetermined value to detect a defect in said object.

15. The inspection device of claim 14 wherein said second signals indicating the location of said point on the object from which the event signal is generated is also stored in the said random access memory of said event storage means.

16. The inspection device of claim 15 further in cluding reject signal means connected to said random access memory for generating a reject signal for said object when the storage capacity of said random access memory is exceeded.

17. The inspection device of claim 16 wherein said plurality of pixel signals are generated in groups correspond-ing to successive sweeps of associated portions of said object by said photodiode array, each group thereby representing the pixel signals from said associated portion of the object, said interface means further including means for counting said groups of pixel signals.

18. The inspection device of claim 17 wherein said groups of pixel signals are generated in series and said interface means further include selecting means for selecting one or more of said groups for processing by said processing means, said selecting means including a low sweep comparator means for selecting one of said groups in said series as the group at which said processing will begin, and a high sweep comparator means for selecting one of said groups in said series as the group at which said processing will end.

19. The inspection device of claim 18 wherein said processing means includes counter means for counting a number of said event signals representing associated points on the object having a predetermined spatial relationship, and re-ject signal means for generating a reject signal for the object when said number of said event signals exceeds a pre-determined value.

20. The inspection device of claim 1 wherein said interface means include storage means for storing said pixel signals; difference signal means connected to said data sig-nal means for generating difference signals representing the difference in the magnitudes between each of said pixel signals and a preceding one of said pixel signals; threshold signal means for storing a plurality of threshold signals;
event signal means connected to said difference signal means and said threshold signal means for generating said event signals for each of said difference signals which differs from one of said threshold signals by a predetermined amount;
and display means connected to said event signal means for displaying said event signals as a two-dimensional visual representation of the surface of the object being inspected.

21. The inspection device of claim 20 including disabling means for disabling said storage means and wherein said threshold signals have a zero magnitude, whereby the pixel signals pass through said difference signal means and said event signal means to be displayed by said display means, and wherein said display means displays the pixel signals with respect to a pair of orthogonal axes, one of said axes representing the magnitude of the pixel signals and the other one of said axes representing the locations of the associated inspection points along one axis of said object.

22. The inspection device of claims 1, 19 or 21 further including master control means respectively responsive to said first and second control means for alternately connecting one of said first and second control means to said interface means so that one reads a group of said characteristics signals for one object while the other pro-cesses a group of said characteristics signals for a preceding object.

23. An inspection device as recited in claim 1 wherein said interface means compares successive adjacent pixel signals and generates an event signal when the absolute value of the difference between the magnitudes of the adjacent pixel signals exceeds a predetermined threshold value associ-ated with the location of the corresponding point on the object.

24. An inspection device as recited in claim 23 wherein said interface means stores a magnitude characteristic signal having a value equal to the difference between said absolute value and said threshold value.

25. An inspection device as recited in claims 1 or 24 wherein the pixel signals are provided by a photodiode array having a plurality of photodioded, each one providing one of the pixel signals, and wherein said interface means compares successive pixel signals from adjacent ones of the photodiodes.

26. An inspection device as recited in claims 1 or 24 wherein the pixel signals are provided by a photodiode array having a plurality of photodiodes, each providing one of the pixel signals, and wherein said location characteristic signals each represent the position of a photodiode in the photodiode array corresponding to the location of the point on the object from which the event signal is generated.

27. An inspection device as recited in claims 1 or 24 wherein said interface means includes a random access memory for storing said group characteristic signals.

28. An inspection device as recited in claims 1 or 24 wherein said interface means also stores a readable magnitude summation signal for each group of characteristic signals, said magnitude summation signal being equal to the sum of the magnitude characteristic signals generated by a corresponding object; and wherein said first and second control means are also responsive to the magnitude summation signal to provide a reject signal when said magnitude sum-mation signal exceeds a predetermined value.

29. An inspection device as recited in claims 1 or 24 wherein said interface means also stores a readable event summation signal for each group of characteristic sig-nals, said event summation signal being equal to the total number of event signals generated by a corresponding object;
and wherein said first and second control means are responsive to said event summation signal to provide a reject signal when said event summatiomn signal exceeds a predetermined value.

30. An inspection device as recited in claim 24 wherein the pixel signals are provided by a photodiode array having a plurality of photodiodes, each providing one of the pixel signals, and wherein said interface means com-pares successive pixel signals from adjacent ones of said photodiodes to generate a string of event signals; and wherein said first and second control means are responsive to said magnitude characteristic signals to calculate a string magni-tude signal equal to the sum of the magnitude characteristic signals in said string and to provide a reject signal when said string magnitude signal exceeds a predetermined value.

31. An inspection device as recited in claim 30 wherein said interface means generates a plurality of said strings for an object; and wherein said first and second control means are responsive to said magnitude characteristic signals and said location characteristic signals among strings in proximity to each other to calculate a blob magnitude signal equal to the sum of the magnitude characteristic sig-nals among said strings and to provide a reject signal when said blob magnitude signal exceeds a predetermined value.

32. An inspection device as recited in claim 30 wherein said interface means generates a plurality of said strings for an object; and wherein said first and second control means are responsive to said magnitude characteristic signals and said location characteristic signals among strings in proximity to each other to calculate a blob width signal equal to the number of magnitude characteristic signals among said strings and to provide a reject signal when said blob width signal exceeds a predetermined value.

33. An inspection device as recited in claim 30 wherein said interface means generates a plurality of said strings for an object; and wherein said first and second control means are responsive to said magnitude characteristic signals and said location characteristic signals among strings in proximity to each other to calculate a blob area signal equal to the total number of events among said strings and to provide a reject signal when said blob area signal exceeds a predetermined value.

34. An inspection device in an apparatus for detect-ing defects in successive objects and for providing a plural-ity of pixel signals each representing the magnitude of light received from a corresponding point on an object, said in-spection device comprising:
an interface means responsive to successive adjacent pixel signals for generating an event signal when the absolute-value of the difference between the magnitude of adjacent pixel signals exceeds a predetermined threshold value associ-ated with the location of a corresponding point on the object, said interface means storing a readable group of characteristic signals representing the total number of event signals gener-ated by a corresponding object, each characteristic signal including a first signal indicating the magnitude of the corresponding events signal and a second signal indicating the location of the point on the object from which the event signal is generated; and first and second control means respectively respon-sive to successive groups of characteristics signals corre-sponding to successive objects for processing said character-istic signals and providing a reject signal to discard the corresponding object when one of said first and second control means indicates that a rejectable defect is present.

35. An inspection device as recited in claim 34 wherein the pixel signals are provided in a serial format and wherein said interface means comprise means for latching one of said pixels signals, first means responsive to said latching means for comparing one of said pixels signals with a preceding one of said pixel signals in said latching means to provide a difference signal equal to the difference in magnitudes of said pixel signals, means responsive to said first comparing means for providing the absolute-value of said difference signal, means for storing a plurality of threshold signals, and second means responsive to said abso-lute-value means and said threshold storage means for com-paring the absolute-value of each of said difference signals to a correspondingly stored threshold signal to generate one of said event signals when the absolute value of the magnitude of said difference signal exceeds the magnitude of said corresponding threshold signal.

36. An inspection device as recited in claim 34 wherein said interface means further comprises means responsive to said second comparing means for storing a magnitude characteristic signal having a value equal to the difference between said absolute value and said threshold value.

37. An inspection device as recited in claims 34 or 35 wherein said interface means further comprises means responsive to said second comparing means for storing a mag-nitude summation signal equal to the sum of the magnitude characteristic signals generated by a corresponding object.

38. An inspection device as recited in claim 34 wherein said interface means further comprises means respon-sive to said second comparing means for storing an event summation signal equal to the total number of event signals generated by a corresponding object.

39. An inspection device as recited in claim 34 wherein the pixel signals are provided by a photodiode array having a plurality of photodiodes, each one providing one of the pixel signals, and wherein said interface means is responsive to successive pixel signals from adjacent ones of the photodiodes to generate a string of event signals.

40. An inspection device as recited in claim 39 wherein said threshold storing means includes a random access memory for storing a string of threshold values for comparison to a corresponding string of absolute-value signals represent-ing the absolute value of the difference between the magnitude of adjacent pixel signals provided by adjacent photodiodes.

~

41. An inspection device as recited in claim 40 wherein said interface means further comprises means for selecting one of said threshold values associated with a corresponding one of said absolute-value signals.

42. An inspection device as recited in claim 41 wherein said interface means further comprises means for counting the number of said strings of event signals and means for storing a location characteristic signal having a value determined by said threshold selection means and said string counting means.

43. An inspection device as recited in claim 42 wherein said interface means further comprises maximum string means responsive to said string counting means for limiting an allowable number of strings of event signals for each object.

44. An inspection device in an apparatus for detect-ing defects in successive objects and for providing a plural-ity of pixel signals each representing the magnitude of light received from a corresponding point on an object, said in-spection device comprising:
an interface means responsive to the pixel signals for comparing successive adjacent pixel signals and generating an event signal when said comparison indicates the presence of a defect, said interface means storing a readable group of characteristic signals representing the total number of event signals generated by a corresponding object, each characteristic signal including a first signal indicating the magnitude of a corresponding event signal and a second signal indicating the location of the point on the object from which the event signal is generated;
first and second control means respectively respon-sive to successive groups of characteristic signals corre-sponding to successive objects for processing said character-istic signals and providing a reject signal to discard the corresponding object when one of said first and second control means indicates that a rejectable defect is present; and a master control means connected to said first and second control means for alternately connecting one of said first and second control means to said interface means so that one reads a group of said characteristic signals for one object while the other processes a group of said chacter-istic signals for a preceding object.

45. An inspection device as recited in claim 44 wherein said interface means compares successive adjacent pixel signals and generates an event signal when the absolute value of the difference between the magnitudes of the adjacent pixel signals exceeds a predetermined threshold value associ-ated with the location of the corresponding point on the object.

46. An inspection device as recited in claim 45 wherein said interface means stores a magnitude characteristic signal having a value equal to the difference between said absolute value and said threshold value.

47. A method for detecting defects in an object being inspected by an apparatus providing a plurality of pixel signals each representing the magnitude of light re-ceived from a corresponding point on an object, comprising the steps of:
(a) generating an event signal when the absolute value of the difference between the magnitudes of adjacent pixel signals exceeds a predetermined threshold value associated with the location of a corresponding point on the object indicating the presence of a defect at that point;
(b) storing a readable group of characteristic signals representing the total number of event signals gen-erated by a corresponding object, each characteristic signal including a first signal indicating the magnitude of a corre-sponding event signal and a second signal indicating the location of the point on the object from which the event signal is generated;
(c) processing a group of characteristic signals to identify the presence of a defect in a corresponding ob-ject; and (d) providing a reject signal to discard the object when a rejectable defect is identified.

48. A method as recited in claim 47 further com-prising a step of reading a group of characteristic signals for one object while step (c) is processing a group of char-acteristic signals for a preceding object.

49. A method as recited in claims 47 or 48 wherein step (b) also stores a readable magnitude summation signal for each group of characteristic signals, the magnitude summation signal being equal to the sum of the magnitude characteristic signals generated by a corresponding object, and step (c) identifies the presence of a defect when the magnitude summation signal exceeds a predetermined value.

50. A method as recited in claims 47 or 48 wherein step (b) also stores a readable event summation signal for each group of characteristic signals, the event summation signal being equal to the total number of event signals gen-erated by a corresponding object, and step (c) identifies the presence of a defect when the event summation signal exceeds a predetermined value.

51. A method as recited in claim 48 wherein the pixel signals are provided by a photodiode array having a plurality of photodiodes, each providing one of the pixel signals, and wherein step (a) generates a string of event signals for the photodiode array and step (c) identifies the presence of a defect when the sum of the magnitude charact-eristic signals in the string exceeds a predetermined value.

52. A method as recited in claim 51 wherein step (a) generates a plurality of strings for an object and step (c) identifies the presence of a defect when the sum of the magnitude characteristic signals among strings in proximity to each other exceeds a predetermined value.

53. A method as recited in claim 51 wherein step (a) generates a plurality of strings for an object and step (c) identifies the presence of a defect when the number of magnitude characteristic signals among strings in proximity to each other exceeds a predetermined value.

54. An inspection device in an apparatus for detect-ing defects in successive objects and for providing a plural-ity of pixel signals each representing the magnitude of light received from a corresponding point on an object, said in-spection device comprising:
an interface means responsive to the pixel signals for comparing successive adjacent pixel signals and generating an event signal when the absolute value of the difference between the magnitudes of the adjacent pixel signals exceeds a predetermined threshold value associated with the location of the corresponding point on the object, said interface means storing a readable group of characteristic signals representing the total number of event signals generated by a corresponding object, each characteristic signal in-cluding a first signal indicating the magnitude of a corre-sponding event signal, a second signal indicating the location of the point on the object from which the event signal is generated; and output means responsive to said interface means for visual displaying a two-dimensional representation of said characteristic signals.

55. An inspection device as recited in claim 54 further comprising first and second control means respectively responsive to successive groups of characteristic signals corresponding to successive objects for processing said characteristic signals and providing a reject signal to dis-card the corresponding object when one of the first and second control means indicates a rejectable defect is present.

56. An inspection device as recited in claim 55 wherein said interface means stores a magnitude characteristic signal having a value equal to the difference between said absolute value and said threshold value.

57. An inspection device as recited in claims 54 or 56 wherein said representation displayed by said output means uses said location characteristic signals to display the locations of defects on said representation of the surface of the inspected object.

58. An inspection device as recited in claims 54 or 56 wherein said representation displayed by said output means uses said location characteristic signals and said magnitude characteristic signals to display the magnitude characteristic signals at the locations of the defects on said representation of the surface of the inspected object.

59. An inspection device as recited in claim 56 wherein said threshold values have a magnitude of zero and said representation displayed by said output means uses said magnitude characteristic signal to display the absolute-value signal at all corresponding points on said represen-tation of the surface of the inspected object.

60. An inspection device as recited in claim 56 wherein the pixels are provided by a photodiode array having a plurality of photodiodes, each providing one of the pixel signals, and wherein said interface means compares successive pixel signals from adjacent ones of said photodiodes to gen-erate a string of said event signals, said interface means generating a plurality of strings covering the surface of the inspected object.

61. An inspection device as recited in claim 60 wherein said representation displayed by said output means is accomplished on a pair of orthogonal axes, one of said axes displaying the number of strings covering the surface of the inspected object and the other one of said axes using said location characteristic signals to display the location of each defect in each one of said strings.

62. An inspection device as recited in claim 60 wherein said representation displayed by said output means is accomplished on a pair of orthogonal axes, one of said axes displaying the number of strings covering the surface of the inspected object and the other one of said axes using said location characteristic signals and said magnitude characteristic signals to display the magnitude characteristic signals at the locations of each defect in each one of said strings.

63. An inspection device as recited in claim 60 wherein said threshold values have a magnitude of zero and wherein said representation displayed by said output means is accomplished on a pair of orthogonal axes, one of said axes displaying the number of events in a string and the other one of said axes using said magnitude characteristic signals to display the absolute-value signal at all corre-sponding points in said string.

64. A method for detecting defects in an object being inspected by an apparatus providing a plurality of pixel signals each representing the magnitude of light re-ceived from a corresponding point on an object, comprising the steps of:
(a) generating an event signal when the absolute value of the difference between the magnitudes of adjacent pixel signals exceeds a predetermined threshold value associated with the location of a corresponding point on the object indicating the presence of a defect at that point;
(b) storing a readable group of characteristic signals representing the total number of event signals gen-erated by a corresponding object, each characteristic signal including a first signal indicating the magnitude of a corre-sponding event signal and a second signal indicating the location of the point on the object from which the event signal is generated; and (c) displaying a two-dimensional representation of said characteristic signals.

65. A method recited in claim 64 wherein step (c) displays a representation by using the location characteristic signals to indicate the locations of the defects on the re-presentation of the surface of the inspected object.

66. A method as recited in claim 64 wherein step (c) displays the representation by using the location charac-teristic signals and the magnitude characteristic signals to indicate the magnitude characteristic signals at the lo-cations of the defects on the representation of the surface of the inspected object.

67. A method as recited in claim 64 wherein the threshold values have a magnitude of zero and said step (c) displays a representation using the magnitude characteristic signal to indicate the absolute-value signal at all corre-sponding points on the representation of the surface on the inspected object.

68. A method as recited in claim 64 wherein the pixel signals are provided by a photodiode array having a plurality of photodiodes, each providing one of the pixel signals, and wherein step (a) generates a plurality of strings of event signals fpr an inspected object, each string in-cluding the event signals for the photodiode array.

69. A method as recited in claim 68 wherein step (c) displays a representation including a pair of orthogonal axes, one of the axes indicating the number of strings covering the surface of the inspected object and the other one of the axes using the location characteristic signals to indicate the location of each defect in each one of the strings.

70. A method as recited in claim 68 wherein step (c) displays a representation including a pair of orthogonal axes, one of the axes indicating the number of strings cover-ing the surface of the inspected object and the other one of the axes using the location characteristic signals and the magnitude characteristic signals to indicate the magni-tude characteristic signals at the locations of each defect in each one of the strings.

71. A method as recited in claim 68 wherein the threshold values have a magnitude of zero and wherein step (c) displays a representation including a pair of orthogonal axes, one of the axes displaying the number of events in a string and the other one of the axes using the magnitude characteristic signals to indicate the absolute-value signal at all corresponding points in the string.

72. The inspection device of claims 1, 11 or 19 further including master control means respectively respon-sive to said first and second control means for alternately connecting one of said first and second control means to said interface means so that one reads a group of said char-acteristic signals for one object while the other processes a group of said characteristic signals for a preceding object and event display means connected to said master control means for displaying said event signals as the output of the inspection device in a two-dimensional visual representa-tion of the surface of the inspected object