Method and apparatus for inspecting liquids in transparent containers

• US 4,087,184 A
• Filed: 04/16/1976
• Issued: 05/02/1978
• Est. Priority Date: 09/12/1974
• Status: Expired due to Term

• Current Assignee: Schering Corporation (Merck & Co., Inc.)
• Original Assignee: Schering Corporation (Merck & Co., Inc.)
• Inventors: Knapp, Julius Z., Zeiss, John C.
• Primary Examiner(s): McGraw, Vincent P.
• Application Number:
  US05/677,593
• Time in Patent Office: 746 Days
• Field of Search: 356/197, 356/240, 250/227, 250/223 B
• US Class Current: 356/427
• CPC Class Codes: G01N 21/9027 in containers after filling
• CPC Class Codes: G01N 33/0081 Containers; Packages; Bottles

Abstract

A method and apparatus for automatically inspecting liquid filled containers for particulate contaminants in relative size. The method comprising the steps of illuminating the liquid with a constant intensity light source, imaging the entire illuminated liquid volume, including the meniscus, into a plurality of image planes with fiber optic bundles, and monitoring the fiber optic bundles with an array of constant sensitivity photo transducers. Each photo transducer continually translates the illumination value of the vial image of an assigned and separate unit volume of the liquid-filled container into a voltage signal and each signal is monitored for a signal change indicative of particulate movement. The interfering output signal due to the meniscus 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 transducers.

Claims

1. A method for inspecting illuminated articles wherein each of said articles comprise a liquid-filled transparent container, that may have a multiplicity of optical defects or specular reflections on or in itself which liquid is to be inspected for the presence of foreign particles, said method comprising the steps of:

a. rotating said article to cause the liquid contents to rotate therein,

b. placing the rotating article at an inspection station having associated article illuminating means,

c. stopping the rotation of said container,

d. imaging the article along a first viewing axis with image forming means,

e. while the illuminated liquid continues to rotate, dissecting said article image into a plurality of detection areas which extend from the bottom of the container through the top of the liquid meniscus,

f. monitoring each of said detection areas with individual sensing means only for changes in illumination below the saturation limit of said sensing means,

g. electronically translating said changes in illumination into voltage signals,

h. forming a composite signal of said voltage signals,

i. comparing said composite signal to a standard reference signal and based thereon accepting or rejecting said article for particulate contamination;

whereby the image of said foreign particles which moves past a detection area with a saturated sensing means will be detected as it passes through a detection area with an unsaturated sensing means.

2. A method as in claim 1 wherein said dissected image is monitored at a plurality of image planes about which a suitable zone of sharp focus exists.

3. A method as in claim 2 wherein said plurality of sharply focused image planes are monitored by a plurality of stepped fiber optic bundles.

4. A method as in claim 1 wherein the article is imaged along a second viewing axis which is spaced approximately 90°

from the first viewing axis, said viewing axes being directed downwardly toward the liquid meniscus at approximately 15°

to the stationary liquid surface.

5. A method as in claim 1 wherein said detection areas are spaced columns parallel to the axis of rotation.

6. A system for inspecting a liquid filled container for particulate contamination comprising:

a. a source of radiation directed at said liquid filled container,

b. means to rotate said liquid filled container about an axis,

c. means to feed said rotating container to an inspection station,

d. means to stop the rotation of said container,

e. means to image said liquid filled container along a viewing axis,

f. fiber optic bundle means to monitor the image of said liquid filled container at a plurality of parallel columns extending from the bottom of the container through the top of the rotating liquid,

g. sensing means to translate the illumination value monitored by said fiber optic bundle means into a voltage signal,

h. means to transmit only changes in said voltage signals,

i. means to form a composite signal of said transmitted voltage signals,

j. means to accept or reject said liquid filled container based upon a comparison of said composite signal to a standard reference signal.

7. A system as in claim 6 wherein said source of radiation comprises a 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 said fiber optic bundle monitoring means to said container so that said light paths intersect in said container and illuminate substantially all of said liquid and form an angular shadow zone wherein said fiber optic bundle monitoring means is situated.

8. A system as in claim 6 wherein said sensing means is a constant sensitivity photo transducer.

9. A system as in claim 8 wherein said transmitting means is a differentiator.

10. A system as in claim 6 wherein said source of radiation is a light source of constant intensity.

11. A method for inspecting the meniscus of a rotating liquid in a transparent stationary container for particulate contamination comprising the steps of:

a. rotating said container,

b. feeding said rotating container to an inspection station,

c. illuminating said meniscus,

d. monitoring said meniscus at two volumetric portions, in which the voltage signals generated by the meniscus decay would be substantially similar, for changes in illumination due to moving particulate matter and meniscus decay,

e. electronically translating each of said changes in illumination into a voltage signal,

f. substantially eliminating the voltage signals due to the meniscus decay by electronically subtracting the voltage signals originating in one portion from the voltage signal originating in the other portion,

g. forming a composite signal of all of said moving particulate matter voltage signals,

h. comparing said composite signal to a standard reference signal and based thereon accepting or rejecting said liquid filled container for particulate contamination.

12. A method as in claim 11 wherein the meniscus is separately monitored along two viewing axes spaced 60°

-120°

from one another.

13. A method as in claim 12 wherein said viewing axes are spaced approximately 90°

from one another.

14. A method for inspecting illuminated articles, wherein each of said articles comprise a liquid filled transparent container, which liquid is to be inspected for the presence of foreign particles, said method comprising the steps of:

a. rotating said article about an axis below the speed that will cause cavitation and bubbling of the liquid,

b. placing the rotating article at an inspection station having associated article illuminating means,

c. stopping the rotation of said container,

d. electronically dissecting said illuminated rotating liquid volume into a meniscus volume image and a sub-meniscus volume image,

e. monitoring said sub-meniscus volume image for changes in illumination which are indicative of moving particulate matter,

f. monitoring said meniscus volume image at two portions, in which the changes in illumination generated by the meniscus decay would be substantially similar, for changes in illumination which are indicative of moving particulate matter and the meniscus decay of the rotating liquid,

g. electronically translating each of said changes in illumination into voltage signals,

h. substantially eliminating the voltage signals due to the meniscus decay by electronically subtracting the voltage signal originating in one portion from the voltage signal originating 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,

j. comparing said composite signal to a standard reference signal and based thereon accepting or rejecting said liquid filled container for particulate contamination.

15. A method as in claim 14 wherein said sub-meniscus volume image is monitored from a first time immediately after the rotation of said container is stopped, and said meniscus volume image is monitored from a second time subsequent to said first time.

16. A method as in claim 14 wherein said two portions are the meniscus image edge portions and said meniscus image is further separately monitored at a center portion located between said two edge portions.

17. A method as in claim 16 wherein said sub-meniscus volume image is monitored from a first time immediately after the rotation of said container is stopped, said meniscus center portion image is monitored from a second time subsequent to said first time and said meniscus edge portion images are monitored from a third time subsequent to said second time.

18. A method as in claim 14 wherein said rotating liquid volume image is dissected into a plurality of columns parallel to said axis, said columns being further dissected into a plurality of unit areas, wherein said sub-meniscus volume image is monitored by the unit areas at one end of said columns and the meniscus volume image is monitored by the remainder of said unit areas.

19. A method as in claim 18 wherein said unit areas are rectangular.

20. A method as in claim 18 wherein the monitoring of steps (e) and (f) is effected by a plurality of fiber optic bundles, each of which are operatively connected to one of said unit areas.

21. A method as in claim 20 wherein the electronic translating of step (g) is effected by an array of constant sensitivity photo transducers, each of said transducers being operatively connected to one of said fiber optic bundles.

22. A method as in claim 14 wherein said composite signal comprises a composite of the magnitude of all of said moving particulate matter voltage signals.

23. A method as in claim 14 wherein said composite signal comprises the integral of all of said moving particulate matter voltage signals.

24. A method as in claim 14 wherein said composite signal comprises any moving particulate matter signal detected over a certain predetermined value.

25. A system for inspecting a liquid filled container for particulate contamination comprising:

a. a source of radiation directed at said liquid filled container,

b. means to rotate said liquid filled container about an axis,

c. means to feed said rotating liquid filled container to an inspection station,

d. means to stop the rotation of said container at said inspection station,

e. means to electronically dissect the image of said rotating liquid into a meniscus volume image and a sub-meniscus volume image,

f. means to monitor said sub-meniscus volume image for changes in illumination due to moving particulate matter,

g. means to monitor said meniscus volume image at two portions, in which the changes in illumination generated by the meniscus decay would be substantially similar, for changes in illumination due to moving particulate matter and the meniscus decay of the rotating liquid,

h. means to electronically translate said changes in illumination into voltage signals,

i. means to substantially eliminate the voltage signals due to the meniscus decay by electronically subtracting the voltage signal originating in one portion from the voltage signal originating in the other,

j. means to form a composite voltage signal of all of said moving particulate matter voltage signals,

k. means to compare said composite signal to a standard reference signal, and means to accept or reject said container based thereon.

26. A system as in claim 25 wherein said means for monitoring said meniscus and said sub-meniscus volume images comprise an array of constant sensitivity photo transducers.

27. A system as in claim 25 wherein a fiber optic bundle means is used as the means to dissect the image of the rotating liquid.

28. A method for inspecting illuminated articles wherein each of said articles comprise a liquid-filled transparent container, which liquid is to be inspected for the presence of particles, said method comprising the steps of:

a. placing the article at an inspection station having associated article illuminating means,

b. rotating said article to cause the liquid contents to rotate therein,

c. stopping the rotation of said container,

d. while the illuminated liquid continues to rotate, imaging diverse portions of said article at a plurality of sharply focused image planes located along at least one viewing axis,

e. monitoring each of said image planes for changes in illumination which are indicative of said particles,

f. electronically translating each of said changes in illumination into voltage signals,

g. forming a composite signal of all of said particle signals, and

h. comparing said composite signal to a standard reference signal and based thereon accepting or rejecting said article for particulate contamination.

29. A method as in claim 28 wherein said plurality of sharply focused image planes are monitored by a plurality of stepped fiber optic bundles.

30. A method as in claim 28 wherein said image is separately monitored along two viewing axes spaced at 60°

-120°

from one another.

31. A system for inspecting a liquid filled container for particulate contamination comprising:

a. A source of radiation directed at said liquid filled container,

b. means to rotate said liquid filled container,

c. means to feed said liquid filled container to an inspection station,

d. means to stop the rotation of said container,

e. means to image diverse portions of said article at a plurality of sharply focused image planes located along at least one viewing axis,

f. means to monitor each of said image planes for changes in illumination which are indicative of said particles,

g. means to electronically translate said changes in illumination into voltage signals,

h. means to form a composite signal of all of said particle signals, and

i. means to compare said composite signal to a standard reference signal, and means to accept or reject said container based thereon.