CA1074887A - Method and apparatus for inspecting liquids in transparent containers - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method and apparatus for automatically inspecting liquid filled containers for particulate contaminants in relative size. The method comprising the step of illuminating the liquid with a constant intensity light source, dissecting the image of the entire illuminated liquid volume with fiber optic bundles and monitoring the fiber optic bundles with an array of constant sensitivity photo sensors. Each photo sensor continually translates the illuminations value of an assigned and separate cross-sectional unit area of the vial image into a voltage signal and monitors each signal for a signal change indicative of particulate movement. The interfering output signal die to the maniscus decay is corrected, and the accept/reject decision is based upon a composite signal representative of all the differentiated signals received from the array of photo sensors.

Description

July 24~ 1975 207'7 Canada ~074887 JB/la For inspection of the bulk of the liquid, ~he image is preferably dissected into colurnns extending the full height Or the image. For inspection of the meniscus, the meniscus image is preferably monitored at two portions where the signals generated by meniscus decay are subs~antially identical, and the signals due to meniscus decay are elimina-ted by subtracting one signal from the other.

The system comprises:
means for illuminating said container and liquid;

means ~or rotating said liquid-filled container about an axis;

means for abruptly stopping the rotation of said con-tainer;

sensing means for monitoring changes in the light scat-tered by selected portions of said liquid-filled container and for translating said ohanges into voltage signals;

means for ~orming a composite signal of all of said voltage signals; and means for accepting or reJecting said liquid-filled con-tainer based upon a comparison Or said composite slgnal with a standard reference signal.

~ -July 24, 1975 ~077-FTE-2 JB/la This invention relates to a method and apparatus ~or inspecting liquid-rilled ~ransparent containers of any size ~or particulate contamination and especially to a method and apparatus ror detecting the presence of particulate matter in ampoules, bottlesJ ~lasksJ syringes or vials.

The art of inspecking liquid-filled containers, especially vials and ampoulesJ for the presence o~ particulate matter is a relatively old and crowded one as exempli~ied by U.S.
Patents Nos. 2~132J447J ~J4269355J 2,531J529~ 3~029,349, :~
~,217g 877, 3, ~15,997, 3,496~369~ 3,5~8,51~4, 3,598J 907, 3,627,423, 3,777,169, and 3,8~o,969. In most of the rore-going U.S. Patents (as in the present case), the inspection process includes the steps o~ rotating a container to be inspected, suddenly stopping the rotation of the container, -and then inspecting the illuminated rotating ~luld ~or ~oving particles. This simpli~ies detection o~ particles since a moving illuminated particle can be easil~ detected and is readily distinguishable ~rom the stationary reflections which result ~rom imperfections in the container.
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Many prior art systems have been developed which inspect liquid-~illed transparent containers with one or more photo transducers ~or both lar~e particles (e.g~ glass fragments) and ~ine particles ~below 50 micronsj suspended in the rotatlng liquid. The rotating liquid eddy or vortex pro-:,'' ' ' , ' , :
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:, July 24J 1975 10748~'7 JB/la duces in the illumination signal a change that is indistin-guishable rrom a signal due ~o a moving particle. The systems of the prior arl- there~ore have to wait ~or the vortex to disappear before the photo transducer can make an accurate reading o~ particulate movement. How~verJ
when small particles are present, there is a considerable possibility that they will rise to the meniscus and be flung to the wall o~ the container by centri~ugal forceJ
where they can cling and thereby avoid detection~ The systems of the prior art, e.gO o~ U.S, Patent 295~1~529, were able to eliminate the e~eck of the vortex signal only by blocking it until it was no longer appreciable.
However, none o~ the systems of the prior art reco~nized that the interference due to the vortical meniscus decay at the liquid-container interrace could be corrected -thereby allowing a ~aster and more accurate inspection o~ the rotating menlscusD

Prior art systems have generally used only one or two photo transducers each o~ which is directed at the entire rotatin~ solution, but some (e.gO U.SO Patent 2,1329l~47) have used a plurality Or photo transducers aligned in the verti~al direction to allow portions o~ the container to be prefer~ntially examined. I~ specular reflections ~rom either the sur~ace Or the liquid or optical ~laws in the container are o~ su~icient intensity, a photo . ., - 3 ~
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~7 ~ ~7 Jo77 24 l975 JB/la transducer ~lill saturate (i.e., generate its pe~k voltage).
It is impossible to detect any change in illumination due to movement of particles in the liquid volume monltored by a saturated photo transducer~ The movement of the particles is strongly horizontal, so that ir one of the vertically aligned photo transducers is saturatedJ any particle in the liquid zone of that particular photo trans-ducer will not be de~ected.

In prior art systems, the rotating liquid is generally monitored along one or two viewing axes, a single image plane being ~ormed perpendicular to each axis. When a light-sensitive or heak-sensitive composition is being monitored, the intensity of the light source must be re-duced, so that the aperture of the imaging lens must be widened. As a result, the depth of focus ~or the particles o~ interest becomes substantially less. When the depth o~ ~ocus is less than the diameter Or the article being inspected, the inspection period must be lengthened to ensure that a particle Or interest will be detected as i~ ~asses through the sharply ~ocused volume.
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An ob~ect of the lnvention is to provide an improved system and method ~or inspecting llquids in transparent containers ~or particulate contamination~ and in parti~
oular a system and method whereby the rotating meniscus . .: .
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~7~8~7 can be inspected for particulate contamination, and whereby the depth of focus can if necessary be lengthened so that heat-sensi-tive or light-sensitive compositions, or compositions in wide containers, can be rapidly inspected.
According -to one feature of the invention, there-fore, there is provided a method for inspecting liquid-filled transparent containers for the presence of foreign particles in the liquid, said method comprising the steps of:
a) placing the container at an inspection station, b) rotating said conta.iner about an axis to cause the liquid conten-ts to rotate therein at a speed below -that causing cavitation and bubbling of the liquid, c) abruptly stopping the rota-tion of said container so that the liqu.id and particles therein continue to ro-tate, d) illuminating said container and liquid, e) imaging the container along a viewing axis with image-forming means, f~ while the illuminated liquid continues to rotate, dissecting said image into a plurality of detection areas which extend continuously through the sub-meniscus part of the liquid image and substantially from the bottom thereof up to the meniscus, , .

~7~ 7 g) monitoring each of said detection areas, wi.th individual sensing means, for chanyes in light incident thereon below the saturation limi-t of said sensing means, h) electronically tra~slating each o:E said changes in incident light into a voltage signal, i) forming a composite signal of said voltage signals, j) accepting said container or rejecting it according to its particulate contamination when the composi-te signal attains or exceeds the value of a standard reference signal.
According to a further feature of the invention, there is provided a system for inspecting a liquid-filled trans- .
parent container for particulate contamination, comprising:
a) means for illuminating said liquid-f:illed container, b) means for rotating said llquid-filled container about an axis, c) means for ahruptly stopping the rotation of said container, 6- :~

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d) means for imaging said liquid-filled container along an axis, e) sensing means responsive to light incident thereon for moni-toring the image of said liquid-~illed container at a plurality of detection areas which extend continuously through the sub-meniscus part of the liquid image and sub-stantially fro~ the bo~tom thereof up to the meniscus, f) means for translating changes in the response of the sensing means into voltage signals, g) means for forming a composite signal of said voltage signals, and h) means providing an output signal on the basis of which said container may be accepted or rejected according to its particulate contamination when the composite signal attains or exceeds the value of a standard reference signalO
In the method and system of the present invention, the container to be inspected is illuminated by a source of radiant energy. Any appropria-te source of radiantenergy, such : as visible light(with single or multiple bundles of '':

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~0 ~4887 July 24~ 1975 JB/la optical-glass ribers which are used in U.S. Patent 3,627,423) or ultraviolet or infrared light can be used.
The pre~erred mode of illuminatlon is as described in U.S~ Patent No. ~,627,42~, which is herein incorporated by re~erence. A means ~or holding the light source at a constant intensity is desirable, however, especially whenever it is desired to classify contaminants according to their sizes, as in inspection o~ drugs intended ~or parenteral administratiorlg when the relative sizes of the particulate matter are important.

The liquid-~illed container is rotated at a speed surri-cient to rotate the liquid and any particles t~erein; but below the speed that wlll cause cavitation and bubbling o~
the liquid. The container is preferably rotated about a vertical axis givin~ any particles therein a strongly horizontal motion. The container can of course be rotated about a non-vertical axls, when the motion o~ any particles therein will be predomlnantly in planes perpend~cular to the axis of rotation. The rotation of the container is th~n suddenly stopped. Particles moving in the liquid or on .
its surface are illuminated not only by direct rays from the light source but also by rays reflected rrom the sur-. .
~aces o~ the container. TAe moving particles show up as moving spots of light or shadow, sometimes of varying "~ ' '~' ,~'` ' ',,:
, July ~4, 1975 ~0 74887 ~077-FTE_9 intensity, and are thus reaclily distinguished ~rom scratohes, flaws) stains and other optical de~ects ln the walls of the stationary container and from par-ticles, dust, lettering or art work that may be on the ; 5 outside of the container, which show up as stationary spots of light or shadow Or constant intensity.

The container image, as formed by an image-~orming means5 is dissected by a plurallty of ~iber optic bundles into a number o~ vertical columns which extend ~rom the bottom o~ the container through the top o~ the liquid meniscus.
The columns are ~urther subdivided into a plurality o~
unit rectangular areas with each unit area monitored by a di~erent fiber optic bundle. Each unit rectangular area corresponds to a unit volume o~ the container, whose -~
imag~ ~alls thereon. The light incident on each ~iber ! optic bundle is electronically translated into a voltage signal by a constant sensitivity photo.transducer. The signals ~rom the photo transducers are processed through a di~ferentiator so that it is only changes in incident light that are recorded~ There~ore the light of constant intensity !
that is scattered by container imper~ections, lettering, art work and specular re~lectlons yields a constant signal in the photo transducer~ which on di~ferentiation is elimi-na~ed. Any constan~-sensitivity photo transducer~ i.e.

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July 2~, 1975 ~(~17 4~3~ JB/l a one that within its operating range generates an output signal that is in substantially direct proportion to the incident light, can be used. By so utilizing a number of vertical columns, the image of particulate matter moving across a column with a saturatecl photo transducer will be detected as it moves across a column with an unsaturated photo transducer, and a particle passing through a unit volume Or the container that is obscured by lettering or art work on the container will be detected as it passes through an unobscured unit volume. 0~ course, non-vertical columns or any other appropriate detection areas can be used so long as the detection areas are aligned to intersect the paths of particle motion. - -~

The fiber optic bundles and the array of photo transducers .
are pre~era~ly grouped into block areas which permit dif- li ferent parts o~ the image o~ the rotating liquid, in parti~
cular the central meniscus volume, the two edge meniscus volumes on either side thereof and the volume of the re-.. . .
mainder of the rotating liquid to be separately monitored. -~
The lower part o~ the image o~ the rotating liquid, below the maximum downward meniscus displacement~ may be .:
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monitored for particulate contamination by the lower unit rec~angular areas o~ khe vertical columns immediately the container has been stopped7 since any changes in incident , , ' ~ .
' ' ' ' '' - 10 -July 24, 1975 207'7-FTE-11 lV74887 JB/la light occurring in this submeniscus vo:Lume image will only be ~ro~ moving particulate matter" The central meniscus volume may be monitored shortly therea~ter, when the center o~ the meniscus has substantially reached its rest position and the change in re~le¢ted light there~rom is negligible. This time lag is necessary for identiricatlon of small particles since otherwise the change in reflected light from the center o~ the meniscus would make their identi~ication vir~ually impossible; and the correction ~or meniscus decay (discussed below), if extended over the entire meniscusJ could result in an error signal as great as a signal from a small moving particle.

The circumferential edge o~ the meniscus~ which is in con-tact with the wall of the container~ approaches its rest position more slowly than the center o~ the meniscus. How-ever, ln the system o~ thl~ invention, the olrcum~erential edge o~ the rotating meniscus can also be monitored ~or particulate contamination by compensating for the change ln ; the light re~lected by the decaglng meniscus as it approaches its rest position; the voltage signal generated by the change in the light reflected by the decaying meniscus will henceforth be re~erred to as "the interrering illumination slgnal".
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~074887 July 21~ L975 JB/la The circumferential edge of the meniscus will decay very smoothly to its rest position~ therefore the light scattered at a given time by each o~ two circum~erential edge areas symmetrically disposed on opposite sides o~ the viewing axis wil:L be substantially identical, so that the changes in light scattered there at a given time will also be subs~antially identicalO Accordingly, if two volumetric portions of the meniscus edge~ in which the interfering ;~
illumination signals due to the meniscus decay are sub-stantially identical~ are monitored, and the interrering illumination signal originating in one portion is subtrac-ted ~rom the interfering illumination signal originating in the other portion, the inter~ering illumination signal due to the decay o~ the two meniscus edge portions is sub-stantially eliminated, and any signal remaining will besubstantially due to particulate movement alone. ~he me-niscus edges can be monitored in this manner for particulate ; contamination as soon as the center of the meniscus has sub-stantially reached its rest position as discussed abo~e.
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The maximum error signal which results ~rom this meniscus correotion s~ep is o~ small magnitude and can be easily distlnguished ~rom signals due to particulate mov~ment. ~-I~ an even greater sensitivity is desired, however, the inspe¢tion of the edges can be delayed until shortly a~ter inspection o~ the meniscus center. By wai~ing this slight :.
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~74~87 Jllly 24 1975 Js/la additional time, the maximum error signal which can result ~rom the meniscus correction step will be even smaller. Aocordingly, small particlesJ whose images generate small signalsJ can be detected.

In the inspection o~ parenteral solutions ~or particulate contamination3 a particularly pre~erred embodiment delays the start o~ the inspection of the meniscus edges until shortly after the start o~ the inspection of the central meniscus volume. The signal ~rom each photo transducer is amplified as required and differentiated~ and all dir-~erentiated signals are summed~ The difrerentiated signals indica'ce whether any change in brlghtness occurs in the image of each of the unit volumes monitored~ Change of unit volume brightness after the container is at resk is due to particle movement. The accept/reject decision is based upon the comparison of a standard reference signal with a composite o~ the magnitude o~ the di~erentiated signals, the integral of all such signals, any signal detected over a certain predetermined value,or any combi-nation of these.

The invention fur~her comprises a method ~or inspectingthe meniscus of an illuminated, rotating liquid in a trans-; parent stationary oontainer wherein an image o~ the rotating ::~
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1~74887 July 24 1975 JB/la liquid is monitored for local changes in brightness and said changes in brightness are electroIlically translated into voltage signals, characterised in that the image of the meniscus is moni-tored at two volumetric portions wherein the changes in brightness due to the decay Or the meniscus are electroni-cally translated into substantially identical voltage sig-nalsJ the voltage signals due to the meniscus decay are substantially eliminated by elec'cronically subtracting the voltage signal due to one portion from that due to the other, so that any residual voltage signal indicates particulate contamination at the men.iscus, said residual ; voltage signal is compaxed with a standard reference sig-nal and, based on said comparison~ said container is accepted or rejected for particulate contamination.

According to a ~urther ~eature o~ the invention, there is provided a method ~or inspecting liquid filled transpa-rent containers ~or the presence Or foreign particles in the llquid~ said method comprising the steps of:
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a) placing the container at an inspection stationS

b) rotating said container about an axis to cause the liquid contents to rotate therein at a speed below that causing cavita~ion and bubbling of the liquid, .

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07488~ July 2~9 1975 2077~TE~15 JB/la c) abruptly stopping the rotation o~ sald con-t~iner so that the liqu.id and particles therein contimle to rotate, d) illuminating said container and liquid, e) imagi.ng the container along a viewin~ axis with image-forming means, ~) while the illuminated liquid continues to rotate, electronically dissecting said image into (A) two meniscus volume images comprising at least the two side portions o~ the meniscus image, in which changes in brightness generated by the decaying meniscus are subskantially identical, and (B) a sub-meniscus volume image) ~ ~ .
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g) monitoring said sub~meniscus volume image ~or changes in brightness which indicate moving particulate matter, and monitoring said two meniscus volume images for changes in brightness which indi-cate moving particulate matter and the meniscus decay o~ the rotating liquid, , h) eleotronicall~ translating each of s~id changes in brightness into a voltage si~nalJ and sub- :
stantially eliminating the voltage signals due to the meniscus deaay by electronically subtracting the voltage , . , ., , . , ,-, ~ , . . .

1~74887 Juo77 ~4 1975 JB/la i~

signal caused by changes in one portion ~rom the voltage slgnal caused by changes in the other portion, i) forming a composite signal o~ all of the - .
moving particulate matter signals from said sub-meniscus volume and said meniscus volume, ~) comparing said composite signal with a stan-dard reference signal, and, k) based on this comparison, accepting said liquid-filled container or rejecting it ~or particulate contamination.

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According to yet another feature of the invention, there is provided a method for inspecting liquid-filled trans-: parent containers for the presence Or particles in the liquid, said method comprising the steps o~:
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placing the container at an inspection station;

rotating said container about an axis to cause the liquidcontents to rotate therein at a speed below that causing cavita~ion and bubbling of the liquid;

abruptly stopping the rotation Or said container so that the liquid and particles therein continue to ~otate;
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~4~7 July 2~, 1975 JB/la illuminating said container and liquid~;

imaging diverse portions of sa~,d conta:iner at a plurality Or sharply focused ima~e planes located along at least one viewing axis;

monitoring each o~ said image planes ~or changes in bright-ness indicating said particles;

electronically translating each of said changes in bright-ness lnto a voltage signal;

~orming a composite slgnal o~ said volt~ge signals;

comparln~ said composite signal with a standard reference signal, and 9 based on this comparison~ accepting said container or re~ecting it ~or particulate contamination~

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The invention further comprises a system ~or i.nspecting a liquid-~illed transparent container ~or particulate `: contamlnation9 comprising:

: a) means ~or illuminating sald liquid-~illed con-tainer, .~ b) means for rotating said liquid-filled con-tainer about an axis, ~ .

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July 24~ 1975 20l7-F'TE-18 JB/la c) means for abruptly stopping the rota~ion of said container, d) means for imaging said liquid-rilled con-tainer along an axis~ .

el) means for electronically dissecting said image :. into (A) two meniscus volume images comprising at least the two side portions of the meniscus ima~e~ in which changes in brightness generated by the decaying meniscus are substantially identical, and (B) a sub-meniscus volume image, e ) means .~or monitoring said sub-meniscus volume image for changes in brightness due to moving parti-culate matter, ~ -e3) mPans ~or monitoring said two meniscus volume images for changes in brightness due to moving parti-culate matter and the meniscus decay of the rotating li-quid, ~) sensing means ~or electronically converting the . light incident upon said monitoring means e2) and e3) lnto voltage signals, ~) means ror transmitting only changes in said `~ volkage signalsg . , ' "' .
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7 July 2ll, 1975 JB/la g ) means for substantially eliminating the voltage signals due to the meniscus decay by e:Lectronically sub-tracting the voltage signal originating in one portion from the voltage signal originating in the other portion~

: 5 h) means for forming a composite voltage slgnal of all of said transmitted voltage signals due to moving particulate matter, i) means for comparing said composite signal with a standard reference signal, and 10 ~) means for accepting said container or rejecting it for particulate conkamination on the basis of said com-par-ison.
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According to a rurther reature of the invention~ there is provided a system for inspecting liquid-filled transparent ¢ontainers ~or particulate matter in said liquid and for ~.
classi~ying said particulate matter according to the rela tlve sLze thereof, comprising:
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- a light source o~ constant intensit~ for illuminating said container and liquid; :~
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20 means for rotating said liquld-~illed container about an : axis;

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19 - ., J~l~ 24, 1975 ~ ~ 7 ~ 2077-FTE-20 means for abruptly stopping the rotation of said con-tainer3 sensing means ~or monitoring changes in the light scat-tered by selected portions Or said liquid-filled container and for kranslating said changes into voltage sig~als;

means for forming a composite signal of all o~ said voltage signals; and means ~or accepting or rejecting said liquid-filled con-tainer based upon a comparison of said composite signal with a standard re~erence signal.
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The invention is useful particularly (but not exclusively) ~or the inspection of vials and ampoules conkaining solutions intended for injection.
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For the better understanding of the invention, preferred embodiments thereof will be described with reference to the a¢companying drawings, wherein: ~
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Flg. 1 is a side elevational view of a preferred form o~
system according to the invenkion, showing an array of detectors and a print-out chart9 Fig. ~ is an enlarged schematic ~iew showing the light :; :

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JB/la and shadow zones in the region of the container~ with the array of detectors located in the shadow zone;

Fig. 3 is a partial section taken along the line 3-3 of Fig. 1 showing an array of photo transducers;

Fig. 4 is a partial section taken along the line l~
of Fig. 1 showing fiber optic bundles;

Fig. 5 is a ~ront elevational view of an ampoule image showing the maximum meniscus displacement, the meniscus level at difrerent times, and block areas into which the ampoule imagc is divided9 Fig. 6 is a front elevational view Or an ampoule image showing the disposition of unit areas, each one assigned to and monitored by a photo transducer, within the blook --areas;

: 15 Fig. 7 is a typical graph resulting from a single in- :
spection Or an acceptable ampoule which has a very low degree of contamination by small particles;

Fig. 8 is an illustrative graph o~ an unacceptable ampoule having a low degree of contamlnation by small par-ticles and a few larger particles;

Fig. 9 is a typ~oal graph of an unacceptable ampoule .~ , having a high degree of contamination by both small and large partic1es;

' 7 4~ ~ July 2l~, 1975 0 2077-FTE-~2 JB/la Fig. 10 is a typical graph showing the relation Or the light incident upon a constant-sensitivity photo trans-ducer to the voltage signal generated by the photo trans-ducer, Fig. 11 is a block diagram showing a representative electrical circuit ~or processing the signals ~rom each o~ the transducers;

Fig. 12 is a prererred embodiment which uses two detector arrays with stepped fiber optic bundles for improved depth 10 o~ ~ocus;

Fig. 1~ is a partial section taken along the line 13-13 of Fig. 12; and Fig. 14 is a section taken along the line 14-14 of Fig. 12.
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In Figs. 1 and 2, each o~ cables 2 and 4 oonsists of a ~iber optic bundle 8 withln a protective shield 6. The ends of the cables 2 and 4 are open with one end o~ each connected to a light source 10. The light ~rom the source is transmitted through the riber optic bundle 8 to the oppos-ite ends of the cables 2 and 49 these ends being mounted in ~ixed position behind baffles 12 and 14. Any ligh~

source having an intensity sufficient to llluminate the liquid and particles, and compatible with the viewing means, may be used. A 150 watt 21 volt incandescent lamp, _ 22 -July 2~9 1975 8 ~ 20/ -FT~_2 ~or example General Electric type EKEJ has been found suitable. The light source 10 is maintained at a con-stant lntensity by circuit 11 consisting of a ~iber optic light intensity sampler 1~ which continually monitors the intensity of the lig.ht emitted by source 10, a photo trans- -ducer 15 for generating a voltage signal 17 proportional to the light intensity monitored by sampler 13, and a servo ampli~ier 19 for controlling the current 21 to the lamp 10, based upon a comparison of voltage signal 17 with a stored re~erence level signal 2~. - ;

Turntable 16 is mounted on shaft 18, driven by motor 20 and mounted in a ~ixed position on support 22. Sha~t 18 .
is movable ~ertically by lever 24, which is pivoted at 26 :::
to sha~t 18 and at 28 to fixed support ~0~ Sealed container sn containing solution 52 is placed on turntable 163 and the turntable is lifted by depressing lever 24. As turn- : .
table 16 and container 50 reach the position shown in phantom lin~s in Fig. 2, mi.croswitch 54 is closed and, ; through kimer 56, a~tuates motor ~0 ~or a present time ;; 20 interval to rotate turntable 16, container 50 and solution 52. The speed and time Or rotation are suf~icien~
to cause solution 52 and any particles therein to rotate~
but the speed is below that a~ which cavitation, bubbling and entrapment o~ air may occur in the solution. Instead Or the manual lever system it is of course an obvious ' : - 2~ ~ :
', 7 4 ~ ~7 July 2~, 1975 JB/la expedient and within the scope o~ this invention to raise the bottles on the turntable automatically.

A~ter the container has been spinning for a pre~determined time, it is abruptly stopped to leave the liquid and any particles therein rotating. The image Or the rotating liquid formed by converging lens 33 is immediately in-spected by means of a plurality of fiber optic bundles 31, each ~iber optic bundle 31 being operatively connected to one o~ the photo transduoers ~4 o~ an array 32 of photo transducers. The ~iber optic viewing means is pre~erably directed downwards at an angle o~ about 17 to 37 degrees to the horizontal with the most preferred angle being about 27 degrees. Each of khe fiber optic bundles monitors a unit area o~ the image o~ the rotating liquid~ each unit area corresponding to a unit volume of the rotating li-quid. Each photo transducer gives a predetermined response to any illuminakion value within its operating range (see Fig. 10). All o~ the signals ~rom the photo transducers are processed through an electronic circult 36 and the resultin~ composite output slgnal is graphically printed ~ at recorder 40. Recorder 40 can be u~ed by an inspector ,~
to determine whether the particle content o~ the container 1~ acceptable. 0~ course, when a completely automatic ~ystem is used recorder 40 oan be replaced b~ any standard :
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July ~4, 1975 ~ 07 48 ~7 20/ -FTE-25 signal processor which has a stored acceptable criterion ror the container under inspection, as will be discussed hereina~ter with regard to Fig. 11.

In the method and apparatus of this preferred embodiment o~ the present invention~ the sur~ace Or any particle ln the solution is illuminated by both direct and reflected light. The light means directs at least two light beams ~-at the liquid-filled,container along light paths angularly disposed to the line of sight extending from the ~iber op- ' ' ,tic bundle viewing means to the container so that the light paths intersect in the container and illuminate subskantially ~11 o~ the liquid and form an angular shadow zone wherein .: ' the ~iber optic bundle viewing means is situated. Thls arrangement is illustrated in Fig. 2 and is described for a dlfrerent viewing means in the a~orementioned U.S. Patent No. 3J627J423~

Fig. 3 shows a partial cross-sectional view o~ the photo transducer array 32. Eaoh o~ the photo transducers 34 is operatively connected to one o~ the ~iber optic . .
bundles 31.

', Flg. 4 shows a partlal cross sectional view of the fiber '~:

~ optic bundles 31. The bundles are shown as rectangular ~ ' : , at their viewing ends, so that there is no unmonitored .' .

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July 2~ 1975 ~74~7 2077-FTE-26 JB/la area between adjacent unit areas in each column; how-ever, any shape which enables the conta.iner image to be dissected along vertical columns can be used. Ea~h ~iber optic bundle will of course conform at its opposite end to the shape of its respective photo transducer 34.

Fig. 5 shows the shape o~ the meniscus image at its maximum displacement (level "A'l), at its resting position (level "D"39 : and at two intermediate times while the liquid rotating in the ampoule is slowing down (levels "B" and "C"). The time interval between levels "B" and "C" is abouk the same as the time interval between levels "B" and "A". As can readily be seen ~rom Figo 5J the center portion of the meniscus very rapidl~ approaches its rest position when the container spin is stopped, whereas the edge portions o~
1~ the meniscus approach their rest positions much more slowly owing to the tendency o~ the liquid to climb up the walls o~
.' the container. As a result o~ this characteriskic of the ; meniscus decay, the center portion o~ the menisaus can be monitored soon a~ter the container has stopped spinning~ ..

~owever, the system o~ the present invention makes it . :.
possible to usefully monitor the mehiscus edge areas for .~ particulate contamination~.even while the inter~ering out- .
i put signal ~rom the decaying meniscus is still relatively . ~ . large, by compensating ~or the meniscus decay in a manner :~
hereinbelow described ln relation to Fig. 6.

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' July ~1~, 1975 ~7 ~ J0/ -FTE_27 Fig. 5 further shows the four block areas into which the ampoule image is divided by grollping the detectors. The blocks are selected so that the ampoule may be inspected even though there are error signals originating ~rom the vortex and the resulting meniscus decay. Block I is defined by the area of the ampoule image which extends downwards from a point just below the maximum downward meniscus displacement to the bottom o~ the container.
Block II is defined by the upper central portion of the ampoule image and extends from a point above the maximum meniscus creep on the wall of the container downwards to the upper edge of Block I. Blocks III and IV are de~ined by the upper edge portions of the ampoule image, and the rotat~ng meniscus edge ~alls thereon; these Blocks are positioned above Block I, and are adjacent to and on opposite sides of Block II.
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The ~nspection Or the solution starts the moment the container has stopped spinning. The continuous monitoring o~ Block I is started immediately slnce no inter~ering illumination signal originates in Block I. Block II
is continuously monitored from the moment the inter~
fering illumination signal due to decay at the meniscus center becomes negligible in comparison with tha signal which would be generated by the smiallest moving particle o~ interest, e.g~ the moment the meniscus reaches level "B".

.

. . '~ .

':

~74~87 Ju;ly 24 1975 JB/la Blocks III and IV will each continue to have a sub-stantial interferlng illumination signal due to the meniscus decay even a~ter the inter~ering illumination signal ~rom Block II has become negligible. The pre-ferred system of the present invention electronicallysubtracts one Or the signals generated in Blocks III
and IV ~rom the other. This can be accomplished rOr example by electronically inverting the signal genera-ted in Block IV, as indicated in Fig. 11. Since the interfering illumination signal due to the meniscus decay is substantially the same in both Blocks III and IV, the signal which remains after the subtractlon step will be due primarily to particulate movement, although a slight error signal is possible even after the sub-traction. The maximum error signal which is possiblea~ter the subtraction will decrease as the meniscus ~urther decays, e.g. ~rom level "B" to level "C'~, and lt will probably be necessary to delay the monitoring o~ Blocks III and IV until the maximum possible error . ~
signal arter the subtraction is less than the signal which would be generated by the smallest particle that must be detected. Thus, the smaller the particle that must be detected~ the longer this delay must he~

Fig. 6 shows the ampoule image block areas furthcr divlded ~ ' .

~74~7 July 24, 1975 J~/la into a plurality o~ vertlcal columns~ e.g. A, B, .... F~
with each vertical column extending the length of the rotating liquid volume. Eao~l Or the vertical columns is further subdivided into a plurality of unit rectangular ~ g Al ~ A7~ F~ 7~ and each of the rec-tanæular areas is monitored by one of the fiber optic bundles. The fiber optic bundles allow the unit areas to be clearly de~ined but prevent an unmonitored zone rom occurring between ad~acent vertically spaced rectan-gular areasO (If there were unmonitored zones between ad-; ~acent vertically spaced rectangular areas, then ik is possible that a contaminant particlel whose movement Or oourse is strongly horizontal, oould escape detection by rotating only through these un~onitored zones.) Any number o~ unit areas can be used and this number will o~ coursebe dependent on many ~actors including the container size?
the lighk intensity and the degree o~ particle sensitivity desired.

Since each photo transducer is of' constant sensitivity, ~0 ~t will generate a signal subs~antially proportional to thé intensity ~ the light incident thereon. This signal can be the result o~ specular reflection from the con-talner, a flaw or mark on the sur~ace o~ the container~
menisous decay9 liquid surrace specular reflection~ or partlculake mo~emen~. These signals are rurther processed .
through a differentiator so that only signal changes are "

, - .

~74~ July 2~, 1975 2077-FTE~0 JB/la transmitted. A composite signal for each of the block areas is then compiledO That is, each block area will generate a composite signal of ~11 differentiated signals coming rrom ~hat block area. Container ~laws or marks and specular reflections will generate constant signals and will not contribute to the composite signal. When specular re~lections are suf~iciently intense, the cor-responding photo transducer will saturate at a constant saturation signal (compare Fig. 10) which will not contri-bute to the composite signal. However, if a photo trans-ducer is saturated, a moving particle that may be present ln the volume modulated by that photo transducer will not go undetected, since lt will be detected when it passes through a neighbouring volume modulated by an unsatu-ra~ed photo transducer.

The decaying meniscus image occurring in Blook II willgenerate a signal, but this signal will be negligible and easily distinguishable from a moving particle signal. The decaying meniscus image modulated by Block III will generate a composite dir~erentiated signal which will be very close to the composite differentiated signal from the decaying meniscus image which is generated in Block IV. Subtraction of the composite differentiated signal of Block III from the composite di~ferentiated signal of Block IV will there-~5 fore substantially eliminate the decaying meniscus signalwithin khe liquid volume monitored by these BlocksL The -- ~iO -- ' ~o7~887 July 249 1975 JB/la cornposite signal remaining after this subtraction will indicate only the moving particulate matter present in the meniscus edge. The ~light di~ference in the dir-~erentiated signals which may result from the meniscus 5 r decay seen in Blocks III and IV will be negligible and will accordingly be easily distinguishable ~rom any sig-nal resulting ~rom particulate movement.

Figs. 7 to 9 are schematic views showing the results of single inspections o~ three dif`ferent ampoules. As can be seen rrom the figures~ when an ampoule is ~irst spun a considerable amount o~ inkerrerence is detecteclJ but as the meniscus o~ the spinning liquid approaches its maximum level of displacement, the interference signal decays to an insignificant noise level. Each signal ;
which is observed after the start of the monitoring time indicates a change in incident light resulting from scatter by a moving particle, the height of the peak and the total area of the signal under the peak indicating the type and size o~ the particle observed. For exampleg ;~
a large spherical dark particle will probably generate a low and wid~ signal, while a small highIy re~lective particle will probably generate a bigh~ narrow signal.
A large thin particle will generate a signal that depends on how much sur~ace is presented to the photo transducerO

, .......

, .

~ 6)74887 2077-~11`E~
JB/la I~ the photo transducer ~'sees" only its end then a small signal will be recorded and may be ignored by the signal processor; however, in the present continuous monitoring system such a large thln particle will be detected when it later presents a larger sur~ace to one of the photo transducers. Instead o~ the graphic signal record shown in Figs. 1 and 7 to 9~ any standard signal processor having an acceptable criterion stored therein and con~
sisting of (~or example) an integrator, comparator, peak detector and adder or any combination thereo~ can be used to aocept or re~ect the container.

:
Flg~ 10 shows a graph of the signal generated by a kypical photo transducer against the light incident thereon* As ~an be seen from the graph, the photo transducer will not respond until the incident light is above a certain minimum level called the dark current or noise limit.
Similarly the photo transducer will sat.urate at a certain level Or incident light (the saturation limit)~ and variations in light intensity above this level will go undetected~ Since a constant sensitivity photo trans-ducer is used, there is a substantially straight line relationship ~rom the dark current or noise limit up to the saturation limit in ~he operating range.

.
, ,

- 3~ ~

July 24~ 1975 ~7 48 8 ~ 2077-FTE-33 Fig. 11 shows an electronic circuit (e.g. 36 ln Fig. 1) which can be used to practise this preferred embodiment of the lnvention. In Fig. 11 the light incident on each fiber optic bundle (corresponding to each unit rectangu-lar area) is monitored by a single constant sensitivityphoto ~ransducer, which generates a signal when khe illumination is greater than the noise limit, as shown ;~
in Fig. 10. This signal, if any, is then differentiated and amplified. 'rhe ampli~ied signals from the various unit areas within a block are then summed along the vertical column portions within that block, and the composite signals from the vertical column portions are then summed throughout each block. For each block, the summing amplifier is started at the appropriate time, as discussed above, through a control signal. Once the , ; block summing ampli~ier is operatin~ it continually ampli-~ies signals ~hich can be processed and compared with a standard acceptable criterion, upon which comparison an accept/reject decision can be made. The oomposite signal from Blocks III and IV is formed by continuous electronic subtraction of the composite differentlated sign~l o~ one Block ~rom that of the other Thls can be accomplished by inverting one of the signals (e.g.
positive to ne~atlve) by means o~ the Inverting Amplifier ~5 be~ore the ~inal summation step. The signal processor ` : .

- i... ... ., . . . ,, .. . , . . . :, . . . . . . . . , : .

Jllly 21~, 1975 ~074887 20/ -FTE-~4 can be any device known ~or tha~ purpose~ such as a comparator ~or any peak height over a certain level, an integrator for all slgnals~ a peak detector and adder ~or all signals, or any combination of the above. It is~
o~ course, clear thak this electronic circuit can be modi~ied in numerous ways without departing ~rom the essentials o~ the invention. For exampleJ the amplifier can be omitted, the signals can be ~irst summed horizon-; tally) or the differentiation can take place a~ter one o~ the summing operations.

Figs. 12 to 14 show an especially preferred modi~icationof the above-described embodiment. Fig. 12 shows a stationary container 50 in cross-section with the liquid 52 rotating ln the direction of the arrowsO The images o~ the rotating liquidg as ~ormed by lenses ~3~ are inspec-ted by a plurality o~ stepped ~iber optic bundles 35 along two viewing axes. Any appropriate number of steps in a given ~iber bundle may be used; ~or illustrative pur-poses three steps X~ Y, Z are shown in Figures 12 to 14.
Each fiber optic bundle is divided in~o the same number o~ steps, and each step is continuous for the full length o~ the column~ as clearly indicated in Figs. 1~ and 14.

Fig. 13 shows a partial cross sectional view o~ the stepped fiber optic bundles ~5 similar to Fig. 4.

' ;, .. ~ . . . . ~ :
- . . . . . . .

~74887 20U77 2TE 1975 JB/la Fig. 14 shows a cross sectional view of the stepped ~iber optic bundles 35 similar to the unstepped ~iber optic bundles shown at the lert of Fig. 1.

The stepped ~iber optic bundles 35 have particular utility when the liquid contents under inspectlon are sensitive to light or heat~ so that the intensity o~ the l:ight source must be kept as low as possible to prevent deterioration o~ any ingredient in the liquid. The lower light intensity requires a decrease in the numerical value o~ the lens "~" stop, which inherently decreases khe depth of ~ocus of the lens; e.g.l at a given light intensity, an f4 lens has a smaller range o~ sharp focus for the particles o~ interest than an f8 lens. Thus, apparatus o~ the prior art could analyse liquids that were sensitive to heat or light or that were sealed in wide containers only by excessive ampli~ication o~ the electrical output o~ the photo-transducer or other detector, so that such apparatus became less capable o~ detecting small particles against the nolse-background. Moreovers the inspection time had to be increased to ensure that , any contaminating particle moving in the liquid would .
have sufflcient time to pass through the reduced zone o~ sharp ~ocus and thus be detected.
~ .
" . ~
.,:

.' ... . .
- ~5 ~

.

~74887 20U77 FTR 1675 JB/la With the system illustrated in Figs. 12 to 14, it is possible to ~nspect the entire 3iquid contents much faster and with a higher degree Or reliabilit~ than here-to~ore. The stepped viewing means can also be used to inspect large containers in which the depth of focus of the lens ~3 is considerably less than ~he diameter of ~he container under inspection. For example, at constant image-brightness~ an increase in the light in-tensity and in the f-number of the lens 33 rnight be used to increase the depth of rOcus o~ the lens ~ (provided that the solution 52 is not sensitive to light or heat), but the cost could be unduly high; for, under these oircumstances, the depth of focus Or the lens is pro_ portional to the square of the light intensity, e.g.
to treble the range o~ sharp focus would require a nine-~old increase in light intensity. On the other hand, any appropriate number o~ sharply focused image planes can be used in the modification of Figs. 12 to ]4 depending upon the container size and the desired light intensity.

Other equivalent means can of course be used to increase the number Or sharply focused image planes. For example~
(1) a plurality o~ lens and mirror combinations can be . .
~ used to rOous the image of a plurality of viewing planes -, ` ~ on a single image plane using the hereinabove descxibed : .
' ~

'' ~

July 24, 1975 ~074~387 20~-FTE_~7 unstepped viewing means illustrated in Figs. l, 2 and

4, or ~2) a series of partlally reflective mirrors (e,g. image detector splitters) in combination with a plurality of unstepped viewing means can be used to ~ocus the image o~ a plurality o~ viewing planes on a plurality o~ image planes.

', '~

Figures 12 to 1~ ~urther illustrate a pre~erred variation ;
in which two viewing-axes are used. The viewing axes are pre~erably 60 to 120 degrees apart~ an angle o~ 90 degrees bein,~ most preferred. As in Figs. 1 and ~, the viewing means should be located in the shadow zone i~ the pre~erred, previously discussed lighting means is used. The plural ; ~iewing axes permit a ~aster and more reliable inspection since~ it is easier to detect a particle which is moving essentially parallel to a viewing plane than it is to ; detect a particle moving essentially perpendicular to a viewing plane" If the two ~iewing axes are about 90 de~rees apart, then a particle that is moving almost perpendicularly I to one and thus i8 di~lcultly detectable thereby will be moving almost parallel to the other and thus much more readily detectable by the other. Plural viewing axes can ' o~ course be used with any modification o~ the viewing means previously dlscussed.

~7 ~;

:, !,. - ' : . .. .. -

Claims (34)

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

1. A method for inspecting liquid-filled transparent con-tainers for the presence of foreign particles in the li-quid, said method comprising the steps of:

a) placing the container at an inspection station, b) rotating said container about an axis to cause the liquid contents to rotate therein at a speed below that causing cavitation and bubbling of the liquid, c) abruptly stopping the rotation of said container so that the liquid and particles therein continue to rotate, d) illuminating said container and liquid, e) imaging the container along a viewing axis with image-forming means, f) while the illuminated liquid continues to rotate, dissecting said image into a plurality of detection areas which extend continuously through the sub-meniscus part of the liquid image and substantially from the bottom thereof up to the meniscus, g) monitoring each of said detection areas with indi-vidual sensing means responsive to light incident there-on below the saturation limit of said sensing means, h) electronically translating changes in the response of each sensing means into voltage signals, i) forming a composite signal of said voltage signals, and j) accepting said container or rejecting it according to its particulate contamination when the composite signal attains or exceeds the value of a standard reference signal.

2. A method as claimed in claim 1 wherein the illumina-tion of step d) is effected with light of constant inten-sity.

3. A method as claimed in claim 1 wherein step f) of dissecting said image is accomplished by means of a plu-rality of fiber optic bundles.

4. A method as claimed in claim 3 wherein said step g) of monitoring each of said detection areas is accomplished by monitoring the light incident on each fiber optic bundle by means of a constant-sensitivity photo transducer operatively connected therewith.

5. A method as claimed in claim 4 wherein, in step f), the image is dissected into a plurality of columns paral-lel to the image of the axis of rotation.

6. A method as claimed in claim 5 wherein each column is further dissected into unit rectangular areas enabling the full length of each column to be monitored.

7. A method as claimed in any of claims 1, 5 & 6 wherein, in step (f), the image is dissected in-to a plurality of detection areas that extend from the bottom of the container image through the top of the liquid meniscus image, in step (g), two blocks of detection areas, on which two side portions of the meniscus image fall, and whose associated sensing means generate responses to changes in the image of the decaying meniscus which can be translated into substantially identical voltage signals, are monitored for light incident thereon that is due to moving particulate matter and to meniscus decay, and in step (i), the voltage signals due to the response of the sensing means to the meniscus decay are substan-tially eliminated by electronically subtracting the vol-tage signals originating in one block from the voltage signals originating in the other block.

8. A method as claimed in any of claims 1, 5 & 6 where-in, in step (f) the image is electronically dissected into a plurality of detection areas that extend from the bottom of the container image. through the top of the liquid meniscus image and said detection areas are grouped into blocks defined by (A) at least two meniscus volume images on two of which the two side portions of the meniscus images fall and whose associated sensing means generate responses to changes in the image of the decaying meniscus which can be translated into substantially identical voltage signals, and (B) a sub-meniscus volume image, in step (g) said sub-meniscus volume image is monitored by its associated sensing means for light incident thereon that indicates moving particulate matter, and said two meniscus volume images are monitored by their associated sensing means for light incident thereon that indicates moving particulate matter and the meniscus decay of the rotating liquid, and in step (i) the voltage signals due to the response of the sensing means to the meniscus decay are substantially elimi-nated by electronically subtracting the voltage signal caused by the response of the sensing means to changes in one portion from the voltage signal caused by the rsponse of the sensing means to changes in the other portion, and a composite signal of all of the moving particulate matter signals from said sub-meniscus volume and said meniscus volume is formed.

9. A method as claimed in any of claims 1, 5 & 6 where-in, in step (f) the image is electronically dissected into a plurality of detection areas that extend from the bottom of the container image through the top of the liquid meniscus image and said detection areas are grouped into blocks defined by (A) at least two meniscus volume images on two of which the two side portions of the meniscus image fall and whose associated sensing means generate responses to changes in the image of the decaying meniscus which can be translated into substantially identical voltage signals, and (B) a sub-meniscus volume image, in step (g) said sub-meniscus volume image is monitored by its associated sensing means for light incident thereon that indicates moving particulate matter, and said two meniscus volume images are monitored by their associated sensing means for light incident thereon that indicates moving particulate matter and the meniscus decay of the rotating liquid, and in step (i) the voltage signals due to the response of the sensing means to the meniscus decay are substantially elimi-nated by electronically subtracting the voltage signal caused by the response of the sensing means to changes in one portion from the voltage signal caused by the response of the sensing means to changes in the other portion, and a composite signal of all of the moving particulate matter signals from said sub-meniscus volume and said meniscus volume is formed; and wherein said side portions are the two meniscus image edge portions and said meniscus image is further separately monitored at a center portion located between said two edge portions.

10. A method as claimed in any of claims 1, 5 & 6 where-in, in step (f) the image is electronically dissected into a plurality of detection areas that extend from the bottom of the container image through the top of the liquid meniscus image and said detection areas are grouped into blocks defined by (A) at least two meniscus volume images on two of which the two side portions of the meniscus image fall and whose associated sensing means generate responses to changes in the image of the decaying meniscus which can be translated into substantially identical voltage signals, and (B) a sub-meniscus volume image, in step (g) said sub-meniscus volume image is monitored by its associated sensing means for light incident thereon that indicates moving particulate matter, and said two meniscus volume images are monitored by their associated sensing means for light incident thereon that indicates moving particulate matter and the meniscus decay of the rotating liquid, and in step (i) the voltage signals due to the response of the sensing means to the meniscus decay are substantially elimi-nated by electronically subtracting the voltage signal caused by the response of the sensing means to changes in one portion from the voltage signal caused by the response of the sensing means to changes in the other portion, and a composite signal of all of the moving particulate matter signals from said sub-meniscus volume and said meniscus volume is formed; and wherein said sub-meniscus volume image is monitored from a first time immediately after the rotation of said container is stopped and said meniscus side portion images are moni-tored from a second time subsequent to said first time.

11. A method as claimed in any of claims 1, 5 & 6 where-in, in step (f) the image is electronically dissected into a plurality of detection areas that extend from the bottom of the container image through the top of the liquid meniscus image and said detection areas are grouped into blocks defined by (A) at least two meniscus volume images on two of which the two side portions of the meniscus image fall and whose associated sensing means generate responses to changes in the image of the decaying meniscus which can be translated into substantially identical voltage signals, and (B) a sub-meniscus volume image, in step (g) said sub meniscus volume image is monitored by its associated sensing means for light incident thereon that indicates moving particulate matter, and said two meniscus volume images are monitored by their associated sensing means for light incident thereon that indicates moving particulate matter and the meniscus decay of the rotating liquid, and in step (i) the voltage signals due to the response of the sensing means to the meniscus decay are substantially eliminated by electroni-cally subtracting the voltage signal caused by the response of the sensing means to changes in one portion from the voltage signal caused by the response of the sensing means to changes in the other portion, and a composite signal of all of the moving particulate matter signals from said sub-meniscus volume and said meniscus volume is formed;
and wherein said side portions are the two meniscus image edge portions and said meniscus image is further separate-ly monitored at a center portion located between said two edge portions, said sub-meniscus volume image is moni-tored from a first time immediately after the rotation of said container is stopped, said meniscus edge portion images are monitored from a second time subsequent to said first time, and said meniscus center portion image is separately monitored from a time between said first time and said second time.

12. A method as claimed in any of claims 1, 5 & 6 where-in said composite signal comprises a composite of the magnitude of all voltage signals due to said moving particulate matter.

13. A method as claimed in any of claims 1, 5 & 6 wherein said composite signal comprises the integral of all voltage signals due to said moving particulate matter.

14. A method as claimed in any of claims 1, 5 & 6 wherein said composite signal comprises any signal due to moving particulate matter over a certain predetermined value.

15. A method as claimed in any of claims 1, 5 & 6 wherein, in step g), said dissected image is monitored at a plurality of sharply focused image planes.

16. A method as claimed in any of claims 1, 5 & 6 wherein, in step g), said dissected image is monitored at a plurality of sharply focused image planes by means of a plurality of stepped fiber optic bundles.

17. A method as claimed in any of claims 1, 5 & 6 wherein, in step e); the container is imaged along a second viewing axis which is spaced 60 to 120 degrees from the first viewing axis, said viewing axes being directed downwardly towards the liquid meniscus at 17 to 37 degrees to the stationary liquid surface.

18. A method as claimed in any of claims 1, 5 & 6 wherein, in step e), the container is imaged along a second viewing axis which is spaced approximately 90 degrees from the first viewing axis, said viewing axes being directed downwardly towards the liquid meniscus at approximately 27 degrees to the stationary liquid surface.

19. A system for inspecting a liquid-filled trans-parent container for particulate contamination, compri-sing:

a) means for illuminating said liquid-filled container, b) means for rotating said liquid-filled container about an axis, c) means for abruptly stopping the rotation of said container, d) means for imaging said liquid-filled container along an axis, e) sensing means responsive to light incident thereon for monitoring the image of said liquid-filled container at a plurality of detection areas which extend continuous-ly through the sub-meniscus part of the liquid image and substantially from the bottom thereof up to the menis-cus, f) means for translating changes in the response of the sensing means into voltage signals, g) means for forming a composite signal of said voltage signals, and h) means providing an output signal on the basis of which said container may be accepted or rejected accor-ding to its particulate contamination when the composite signal attains or exceeds the value of a standard re-ference signal.

20. A system as claimed in claim 19 wherein said illu-minating means a) comprises a light source together with light means for directing at least two light beams at said liquid-filled container along light paths angularly disposed to the line of sight extending from the viewing axis of the sensing means e) to said container so that said light paths intersect in said container and illuminate sub-stantially all of said liquid and form an angular shadow zone wherein said monitoring means is situated.

21. A system as claimed in claim 19 wherein said sen-sing means e) include constant-sensitivity photo trans-ducers.

22. A system as claimed in claim 19 wherein said sen-sing means e) include a-plurality of bundles of fiber optics, each bundle corresponding to one detection area.

23. A system as claimed in claim 22 wherein said fiber optic bundles are adapted to dissect the image of said container into a plurality of columns aligned parallel to the image of the axis of rotation.

24. A system as claimed in any of claims 19, 22 and 23 wherein said translating means f) is a differentiator.

25. A system as claimed in any of claims 19, 22 and 23 wherein means e) comprises e1) means for electronically dissecting said image into a plurality of detection areas which extend from the bottom of the container image through the top of the liquid menis-cus image and for grouping said detection areas into blocks defined by (A) at least two meniscus volume images on two of which the two side portions of the meniscus image fall, and whose associated sensing means generate responses to changes in the image of the decaying meniscus which can be translated into substantially identical voltage signals, and (B) a sub-meniscus volume image;

e2) sensing means responsive to light incident thereon for monitoring said sub-meniscus volume image for changes in light incident on said means and due to moving parti-culate matter, and e3) sensing means responsive to light incident thereon for monitoring said two meniscus volume images for changes in light incident on said means and due to moving parti-culate matter and the meniscus decay of the rotating 1;-quid;

means f) comprises means for electronically translating changes in the response of said sensing means e2) and e3) into voltage signals;

and means g) comprises g1) means for substantially eliminating the voltage signals due to the meniscus decay by electronically sub-tracting the voltage signal caused by the response of the sensing means to changes in one portion from the voltage signal caused by the response of the sensing means to changes in the other portion and thereby gene-rating a signal due to moving particulate matter in the meniscus volume, and g2) means for forming a composite signal of all of said transmitted voltage signals due to moving particulate matter.

26. A system as claimed in claim 22 wherein each bundle of fiber optics is stepped, each step being con-tinuous along the column.

27. A system as claimed in any of claims 19, 22 and 23 wherein said illuminating means a) comprises a con-stant intensity light source.

28. A system as claimed in any of claims 19, 22 and 23 wherein the imaging means d) comprises two lenses with optical axes 60 to 120 degrees apart, said axes being directed downwardly towards the liquid meniscus at 17 to 37 degrees to the stationary liquid surface.

29. A system as claimed in any of claims 19, 22 and 23 wherein the imaging means d) comprises two lenses with optical axes approximately 90 degrees apart, said axes being directed downwardly towards the liquid meniscus at approximately 27 degrees to the stationary liquid surface.

30. A method for inspecting the meniscus of an illumi-nated, rotating liquid in a transparent stationary contai-ner wherein an image of the rotating liquid is monitored by light-sensitive means for local changes in light incident on said means and said changes in incident light are electronically translated into voltage signals;

said method including the steps of:

a) monitoring two portions of the meniscus image for light incident thereon, said two portions being selected such that changes in light incident on their associated moni-toring means and due to the meniscus decay are electroni-cally translatable into substantially identical voltage signals;

b) translating changes in said incident light into vol-tage signals;

c) substantially eliminating the voltage signals due to the meniscus decay by electronically subtracting the vol-tage signal due to one portion from that due to the other, whereby any resulting voltage signal indicates particulate contamination at the meniscus; and d) accepting said container or rejecting it according to its particulate contamination when the resulting voltage signal attains or exceeds the value of a standard reference signal.

31. A method for inspecting liquid-filled transpa-rent containers for the presence of foreign particles in the liquid, said method comprising the steps of:

a) placing the container at an inspection station.

b) rotating said container about an axis to cause the liquid contents to rotate therein at a speed below that causing cavitation and bubbling of the liquid, c) aubruptly stopping the rotation of said con-tainer so that the liquid and particles therein continue to rotate, d) illuminating said container and liquid, e) imaging the container along a viewing axis with image-forming means, f) while the illuminated liquid continues to ro-tate, electronically dissecting said image into (A) two meniscus volume images comprising at least the two side portions of the meniscus image, in which changes in brightness generated by the decaying meniscus are substantially identical, and (B) a sub-meniscus volume image, g) monitoring said sub-meniscus volume image for changes in brightness which indicate moving particulate matter, and monitoring said two meniscus volume images for changes in brightness which indicate moving particulate matter and the meniscus decay of the rotating liquid, h) electronically translating each of said changes in brightness into a voltage signal, and substantially eliminating the voltage signals due to the meniscus de-cay by electronically subtracting the voltage signal caused by changes in one portion from the voltage signal caused by changes in the other portion, i) forming a composite signal of all of the moving particulate matter signals from said sub-meniscus volume and said meniscus volume, and j) accepting said container or rejecting it accor-ding to its particulate contamination when the composite signal attains or exceeds the value of a standard re-ference signal.

32. A method for inspecting liquid-filled trans-parent containers for the presence of particles in the liquid, said method comprising the steps of:
placing the container at an inspection station;
rotating said container about an axis to cause the liquid contents to rotate therein at a speed below that causing cavitation and bubbling of the liquid;

abruptly stopping the rotation of said container so that the liquid and particles therein continue to rotate;
illuminating said container and liquid;

imaging diverse portions of said container at a plurality of sharply focused image planes located along at least one viewing axis;

monitoring each of said image planes for changes in bright-ness indicating said particles;

electronically translating each of said changes in bright-ness into a voltage signal;
forming a composite signal of said voltage signals;

and accepting said container or rejecting it according to its particulate contamination when the composite sig-nal attains or exceeds the value of a standard reference signal.

33. A system for inspecting a liquid-filled trans-parent container for particulate contamination, compri-sing:

a) means for illuminating said liquid-filled contai-ner, b) means for rotating said liquid-filled container about an axis, c) means for abruptly stopping the rotation of said container, d) means for imaging said liquid-filled container along an axis, e1) means for electronically dissecting said image into (A) two meniscus volume images comprising at least the two side portions of the meniscus image, in which changes in brightness generated by the decaying meniscus are substantially identical, and (B) a sub-meniscus vo-lume image, e2) means for monitoring said sub-meniscus volume image for changes in brightness due to moving parti-culate matter, e3) means for monitoring said two meniscus volume images for changes in brightness due to moving parti-culate matter and the meniscus decay of the rotating liquid, f) sensing means for electronically converting the light incident upon said monitoring means e2) and e3) into voltage signals, g) means for transmitting only changes in said voltage signals, g1) means for substantially eliminating the voltage signals due to the meniscus decay by electronically sub-tracting the voltage signal originating in one portion from the voltage signal originating in the other portion, h) means for forming a composite voltage signal of all of said transmitted voltage signals due to moving particulate matter, and i) means providing an output signal on the basis of which said container may be accepted or rejected according to its particulate contamination when the composite signal attains or exceeds the value of a standard reference signal.

34. A system for inspecting liquid-filled trans-parent containers for particulate matter in said liquid and for classifying said particulate matter according to the relative size thereof, comprising:

a light source of constant intensity for illuminating said container and liquid;

means for rotating said liquid-filled container about an axis;

means for abruptly stopping the rotation of said con-tainer;

means for dissecting an image of the container and liquid therein into a plurality of columns that extend continuous-ly through the sub-meniscus part of the liquid image and substantially from the bottom thereof up to the meniscus;

sensing means responsive to light incident thereon for se-parately monitoring each of said columns to detect changes in light incident thereon;

means for translating changes in the response of the sen-sing means into voltage signals, means for forming a composite signal of said voltage sig-nals, and means providing an output signal on the basis of which said container may be accepted or rejected according to its par-ticulate contamination when the composite signal attains or exceeds the value of a standard reference signal.