Article Inspection by Successively Televised Images

This invention relates to the inspection of articles by electronic means, and deals more particularly with a method and means for comparing successively televised images of an article to distinguish between apparently stationary desirable characteristics of the article and undesirable characteristics which are moving with respect to these stationary characteristics.

A general object of the present invention is to provide an improved method and means for article inspection wherein successive images of the moving article are compared electronically to generate an error signal whenever the difference therebetween does not fall within a predetermined range.

A more specific object of the present invention is to provide a method and means of article inspection by successively televised images wherein the article being inspected is transparent and contains a liquid which is to be inspected for the presence of foreign particles, said container being rotated on its vertical axis to impart a swirling motion to the liquid so that successive images of the article can be electronically subtracted to produce an error signal only if one or more foreign particles are being moved with the swirling liquid.

In the description to follow, the successive video images of the article undergoing inspection are compared electronically to detect foreign particles inside a transparent container, but it should be understood that the invention is not so limited, and that the method and means of the present invention could be readily adapted for use in detecting dimensional differences between successively formed video images of any moving article. For example, the article being inspected might be a container symmetrical about its vertical axis, and by rotating such an article through successive angular positions for scanning as suggested in the description to follow, the outline of the container can be checked for continuity to detect flaws in its surface, or to detect a "leaner" where the container is a glass bottle or jar. Further, in the inspection of glassware articles or other transparent containers, the internal surface of the container can be readily inspected in a similar manner, and this internal surface inspection can be accomplished simultaneously with inspection of the exterior surface without departing from the scope of the present invention.

FIG. 1 is a schematic view of a presently preferred embodiment well adapted to carry out one method of the present invention for particulate matter detection in glass ampuls.

FIG. 2 is a schematic view showing graphically the results of a single scan of the ampul shown in FIG. 1.

FIG. 3 is a view similar to FIG. 2 but showing graphically the same ampul shown in FIG. 2 at a slightly later instant of time.

FIG. 4 shows the video analog signal of FIG. 2 in inverted position, and the results of adding said inverted signal to the analog signal shown in FIG. 3, with the sum of said signals being indicated graphically at the bottom of this view.

Turning now to the drawings in greater detail, FIG. 1 shows an article 10 which has been positioned at an inspection station by suitable article transfer means indicated generally at 12. The transport means 12 includes a chucking device 14 which permits the article or ampul 10 to be spun on its vertical axis at least momentarily by the motor 16 through a driving connection indicated generally at 18. In the illustrated embodiment, the article to be inspected comprises an ampul having a quantity of liquid 20 therein, and in accordance with the present invention this liquid 20 is to be inspected for the presence of foreign particles as for example the particles indicated generally at 22 and 24. The term article as used herein is intended to represent both the container or ampul 10 and its contents, since the latter represents the portion being inspected.

Still with reference to the inspection station, means is provided for illuminating the transparent container from beneath by a lamp 26 which is shielded as indicated generally at 28 so that illumination from said lamp is directed into the container and by internal reflection remains inside the container for achieving optimum illumination of the foreign particles 22 and 24. In this manner, the liquid itself will not be illuminated appreciably, and will thereby present a dark, or black, background for the television camera 30 in order to provide a contrast for the illuminated particles 22 and 24. Still with reference to the inspection station, a photocell or similar device 32 is provided for indicating to the switching device 34 the presence of an article 10 at the inspection station.

The television camera 30 comprises a conventional component of the present system, being adapted to produce a video output as shown with a single horizontal scanline being indicated schematically at 36 to represent the conventional scanning signal produced by the camera 30. In accordance with the present invention, the camera 30 is driven with vertical and horizontal synchronizing pulses from the output of channels B and C of the memory device 38 respectively. This insures that the camera 30 is operating synchronously with the memory device 38 which may comprise a conventional memory disc of the type commonly used with television cameras generally. Thus, a vertical synchronizing pulse is provided to the switching device 34 and to the television camera 30 as indicated in FIG. 1. The channels B and C of the memory device 38 are impressed with vertical and horizontal synchronizing pulses for the camera 30 such that the memory device 38 and the camera 30 always operate in timed or synchronized relationship with one another. The memory device 38 may comprise a disc, a drum, a delay line, a tape, or other well-known electronic memory device.

In accordance with the present invention, means is provided for storing at least one voltage analog signal from the camera 30 in the memory device 38 for later recall in timed relationship with a succeeding voltage analog signal from the camera 30 for comparison in the comparator 40. As indicated schematically in FIG. 1, the video output or voltage analog signal from the camera is reduced by a quantizer 42 to a simple stretched pulse form, as indicated at 44, whenever a particular horizontal scanline, as for example that shown at 36, is provided with a return which exceeds a predetermined voltage level as indicated generally at 46. Thus, whenever a particle above a predetermined size is detected by the camera 30, and more particularly is detected at a particular horizontal scanline of a particular frame thereof, the video output signal will be simplified in the manner indicated by the quantizer 42.

The initial voltage analog signal 44 will be fed to the memory device 38 through the record line indicated as a result of the switching device 34 being initially located in the position shown. After a predetermined time delay, a second voltage analog signal from the camera 30 is fed directly to the comparator 40 when the switching device 34 is repositioned to its alternate position (not shown), with the result that channel A of the memory disc 38 plays back the recorded voltage analog signal. It will be understood by those skilled in the art that the simple switch shown schematically in reference to the device 34 is intended to represent an electronic switching device for accomplishing this switching function. As a result of the switching device 34 being moved to its alternate position, the voltage analog signal produced by the camera 30 is fed directly to the comparator 40, and the recorded information in channel A of the memory disc 38 is played back to the comparator 40, and both voltage analog signals are synchronized with respect to one another for permitting an electronic comparison to be made by the comparator 40.

Turning now to a more detailed description of the function served by the comparator 40, FIG. 2 shows an ampul 10 with the horizontal scans of the television camera 30 being indicated schematically at a, b, c, d, and e. For purposes of illustration, a glass defect is indicated generally at 21 on the external surface of the ampul 10 and foreign particles 22 and 24 are shown inside the ampul. In accordance with the present embodiment of the invention, wherein it is desired to detect the presence of foreign particles in a liquid contained in the article rather than defects existing on the surface of the article itself, the ampul 10 is first spun about its vertical axis by the mechanism described with reference to FIG. 1, and then its rotation is stopped with the result that the liquid contained therein continues to swirl carrying with it the particles 22 and 24 contained therein. As a result of this, the initial scan of the article 10 by the television camera 14 produces a voltage analog signal as represented schematically in FIG. 2. More particularly, the vertical synchronizing pulse 48 which initiates the frame representing this initial scan is provided to the camera through the synchronizing channel B of the memory device 38. The stationary defect, or dirt particle 21, on the surface of the glass will produce a pulse 50 in the horizontal scanline a as shown. The horizontal scanline c will produce a pulse 52 as a result of the presence of foreign particle 22, and the horizontal scanline e will produce a pulse 54 as a result of the foreign particle 24.

As described hereinabove, and as indicated schematically in FIG. 3, the switching device 34 will operate after a predetermined time delay to take a second look at the ampul 10 producing a second voltage analog of the article at the inspection station, which second analog signal is synchronized with respect to the previous signal being fed to the comparator 40 in the manner described above. As shown in FIG. 3, a vertical synchronizing pulse 58 will be provided to initiate this frame of the camera through the snchronizing channel B of the memory device 38 and the stationary glass defect or particle 21 will appear as a pulse 60 located in the same relationship with respect to the vertical synchronizing pulse 58 as the previous pulse 50 with respect to the previous vertical synchronizing pulse 48. Here again, the pulse 60 occurs on the same scanline a on this frame of the camera. Quite by accident perhaps the foreign particle 22 is also detected on the same horizontal scanline c as indicated by the pulse 62. However, the foreign particle 24 has been moved by the swirling liquid to the scanline d as indicated by the pulse 64 in the example shown.

As previously mentioned, the voltage analog signal indicated generally in FIGS. 2 and 3 are simultaneously fed to the comparator 40, and as indicated schematically in FIG. 4, the first of these two signals is inverted on the same time base so as to be conveniently added to the second signal with the resultant signal being indicated generally at 70 in FIG. 4. It will be readily apparent that the pulses 50 and 60 produced by the stationary glass defect, or particle 21, will cancel one another as indicated generally at 66 in FIG. 4. However, the pulses 52 and 62 associated with the foreign particle 22 do not cancel one another but result in a positive and negative pulse combination which can be used to generate an error signal for operating a reject device 72 in order to remove that particular ampul 10 from other ampuls which do not contain such foreign particles. The pulses 54 and 64 created by particle 24 also produce a positive and negative pulse combination which can be used to generate an error signal. Depending upon the amplitude of the error signal so produced and also on its width, the system described herein can be used to reject ampuls containing particles which exceed some predetermined size .