GB2135768A - Bottle inspection method and apparatus - Google Patents

Abstract

Translucent bottles are inspected for the detection of dirt or foreign bodies by electronically scanning the bottle base in raster fashion and processing the video signal waveform with masking and sampling signals to synthesise three video signals (video 1, video 2 and video 3), video 1 containing information relating to the whole base area, and video 2 and video 3 contain information relating to two part-circular scans of peripheral zones carried out in anti-clockwise and clockwise directions respectively. The discontinuities D are masked out by the frame mask signal, video 1 providing the information for these masked out areas. <IMAGE>

Description

SPECIFICATION Bottle inspection method and apparatus This invention relates to a method and apparatus for detecting the presence of dirt or foreign bodies in translucent bottles, such as glass bottles for containing milk and other beverages. Such inspection apparatus is normally located to inspect the bottles as they are moving along the bottling line conveyor to the filling machine. With modern high speed bottling machinery the apparatus must be capable of inspecting bottles at rates of 800 bottles per minute or more. Bottles which produce signals indicative of the presence of dirt or foreign bodies are rejected from the conveyor line.

Many machines are known employing mechanically moving means for scanning the base area of beverage bottles to detect dirt or foreign bodies.

GB Patent 1,530,927 describes an apparatus using a rotating concave mirror having a radial silvered strip which reflects an image of a radial portion of the base of the bottle onto a photocell. One complete rotation of the mirror is required to image all portions of base successively on the photocell in order to detect the slight diminution of light transmitted through the base caused by the presence of dirt or a foreign body somewhere on the base area.

GB Patent 928,651 describes another apparatus using a spinning Dove prism and lenses to produce a rotating image of the illuminated base area. A number of photocells appropriately placed in the plane of the image inspect annular zones of the bottle for changes in light level indicating dirt or a foreign body. Dividing the base area into zones improves the sensitivity to small foreign objects and enables independent sensitivity control in each zone.

All mechanical scanning systems must have components revolving at high speed if moving bottles are to be inspected successively at rates of say 800 bottles per minute, such as speeds of 1 5 to 30 thousand RPM. Such speeds require high precision components, special lubrication and very skilled maintenance. There is also a further problem in that the central area of the base, being on the rotational axis, is not inspected efficiently. A foreign body in the central area is often not detected. Thus additional inspection means have been proposed to overcome this deficiency as described in GB Patents 1,547,508 and 1,581,392. Electronic scanning overcomes these problemsJof mechanical scanning.Applicants prior GB Patent 1,585,919 overcomes these mechanical problems by providing a photo-diode array on to which is imaged the base of the bottle and which is scanned electronically, raster style, as in television but at extremely high speed (up to 800 complete frames per sec). There are no mechanically moving parts in the scanning system and the foreign object sensitivity is uniform over the whole bottle base area. The video signal from such a scanned array is processed by differentiation so that rapid changes in signal level which correspond to the edges of dirt or a foreign body may generate reject signals which subsequently cause the bottle to be diverted off the conveyor.

Unfortunately, many bottles exhibit a dark annular zone round the outer margin of the base area at the junction of the base and body of the bottle and since the lines of scan will cross this zone, reject signals can be generated at these points even though the bottle is clean. This can be overcome by masking them out with a circular electronic mask signal generated by a PROM addressed in synchronism with the scan as described in GB Patent 1,585,919. This results in an effective inspection area which is slightly less than the base area of the bottle but eliminates the nuisance of a high false rejection rate. However, small objects may be missed if they lie at the extreme edge of the base.

Mechanical scanning systems as discussed above have an inherent advantage when scanning the outer base area since a dark ring is continuous in the circular direction of scan and so does not tend to generate false rejects.

A common defect in bottles is non-uniform glass distribution in the base, such as thin at one side, thick at the other, i.e. a section across the diameter is wedge-shaped. A raster scanned array may indicate a reject with this type of bottle due to the large difference in light transmission at the ends of a diameter. A scan with circular symmetry may not indicate a reject because around the circumference the change is more gradual.

The present invention has for its object to overcome the above-mentioned limitation of the base area which can be inspected by raster scanner systems and to provide a bottle inspection method and apparatus which enables the base of a bottle to be inspected by raster scanning up to the full diameter of the bottle base with low false reject generation when inspecting bottles exhibiting a dark ring or wedge base.

From one aspect the invention consists in the method of bottle inspection for the detection of dirt or foreign bodies therein by electronically scanning the bottle base in raster fashion, characterised by synthesising a first video signal containing information from raster scanning the bottle base, synthesising at least one further video signal containing information from at least part of the peripheral zone of the bottle base, and processing the video signals to generate reject signals indicative of the detection of dirt of a foreign body.

Preferably at least two said further video signals are synthesised containing information from diametrically opposite part-circular peripheral zones respectively.

From another aspect the invention consists in the method of bottle inspection by electronically scanning the bottle base in raster fashion characterised by processing the video signal waveform generated by the raster scanning of the bottle base with masking and sampling signals to synthesise at least three video signals containing information relating to the bottle base and at least two segments of annular zones around the periphery of the bottle base, and processing said at least three synthesised video signals to generate a reject signal if any one of said synthesised video signals indicates the presence of dirt or a foreign body in the inspected bottle.

From a further aspect the invention consists in bottle inspection apparatus for detecting dirt or foreign bodies in bottles, comprising means for electronically scanning the bottle base in raster fashion to generate a video signal waveform, means generating masking signals for eliminating from said waveform video signals outside the area of the base to be inspected, means for differentiating the resultant synthesised video signal, and means for processing a differentiated signal which is indicative of the presence of dirt or a foreign body in the inspected bottle to generate a reject signal, characterised by means for integrating video signals in leading zones of at least some of the lines of said synthesised video signal to generate a first series of integrated signals, means for integrating video signals in terminal zones of at least some of the lines of said synthesised video signal to generate a second series of integrated signals, means for synthesising from said first and second series of integrated signals respectively, second and third synthesised video signals containing information representing changes of each series of integrated signals of said leading and terminal zones, means for generating a reject signal when the rate of change of the signals in said second synthesised video signal exceeds a predetermined value, means for generating a reject signal when the rate of change of the signals in said third synthesised video signal exceeds a predetermined value and means combining the reject signals generated from said three synthesised video signals.

Preferably the apparatus uses a raster scanned photodiode array which has the advantages of high speed, no moving parts, and good sensitivity to small objects, the video output being processed to provide, at the same time, the advantages of scanning the outer zone in a circular manner to the full diameter of the bottle base with very low false reject generation when inspecting bottles exhi biting a dark ring or wedge base.

This desirable result is obtained by the method used to process the video signal waveform from the array. This video signal waveform is used in combination with mask signals and sampled-and-held or integrated portions of the waveform to generate at least three further video signals. One of these contains information (i.e. voltage levels corresponding to illumination levels) relating to the whole base area whilst the other two contain information relating to segments of annular zones on the outer periphery of the bottle base.

Each of these latter two video signals gives in effect a circular scan of a portion of an annular zone of the base area.

The sensitivity in the peripheral zones and the whole base area may be independently varied according to bottling line conditions.

Furthermore, it is possible, to define other substantially circular zones smaller than the outer peripheral one, if desired, and vary the sensitivity of these also.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings, in which: Figure 1 shows a typical video waveform obtained from a scanned photodiode array, Figure 2 shows the image of the base of a bottle projected onto the array, Figure 3 shows the signal from one line, Figure 4 shows timing waveforms used to process the video signal, Figure 5 shows the first synthesised video signal, Figure 6 shows the second synthesised video signal, Figure 7 shows the third synthesised video signal, Figure 8 shows the outer peripheral zones of a bottle which are scanned in a circular direction, Figure 9 is a simplified block circuit diagram of the inspection system.

The apparatus to be described comprises a photo-diode array which is scanned line-byline as more fully described in GB Patent 1,585,919 and provides an output voltage corresponding to the illumination level of each successive diode in each line integrated over the time to scan a complete frame.

Each line signal is the result of interrogating each diode in the line in turn and merging the outputs into a continuous signal for that line.

At the end of each line signal, the voltage drops to zero for a short period before the next line signal starts. A typical video signal for a uniformly illuminated array is shown in Fig. 1.

The image of a bottle base illuminated from below is focussed onto the array by a lens system having adjustable magnification so that, over a range of bottle heights and dia meters, the image can always be made the same size on the array. This size is a little smaller than the array size because with some arrays spurious signals are generared at the start and finish of each line signal and it is easier to gate these out if the bottle image is smaller in diameter than the length of a line.

For example, using an array of 64 diodes per line and 64 lines the image will extend from line 5 to line 60 and on the central lines (31/32) from diode No. 5 to diode No. 60.

This is illustrated in Fig. 2. If larger arrays such as 100 X 100 or 256 x 256 are used the base area image is also arranged to be a constant size which is a little smaller than the array size.

Fig. 3 shows a typical video line signal for line 32 of Fig. 2. The dip in the waveform at C is due to the foreign body shown at the centre of the bottle in Fig. 2. Any other information concerning dirt or foreign bodies in the base (along this line) would appear between the points W and b' in Figs. 2 and 3.

If however Fig. 3 represented line 8, useful information would only occur between the points b" and b" in Figs. 2 and 3.

One step of the method of this invention is to synthesise a first video signal (called Video 1) which only contains useful information and which can be further processed by filtering, differentiation and pulse selection to be described later. A further step is to synthesise at least two further video signals (called Video 2 and Video 3), each of which contains information concerning a part of the outer peripheral zone of the base presented in a sequence which simulates a circular scan of this area. In order to synthesise these video signals a number of masking and timing signals are required which vary for each line of the scan and correspond to various parts of the image of the bottle base on the array.

As illustrated in the block circuit diagram of Fig. 9, the clock signals 100 used to scan the array 101, diode by diode and line by line, are also used to control an address signal generator 102 from which the address signal is applied to a Read-Only-Memory (ROM) 103 which provides, as output, a number of signals synchronised with each video signal, Video 1, 2 and 3 and possibly other video signals, as indicated at Video 4, as will be hereinafter explained. The processing circuitry for Video 1 is represented by block 104 and for Video 2 and Video 3, etc. by blocks 105.

106 is an OR gate in which any reject signals from the video channels are combined to control a common bottle reject mechanism.

Fig. 4 shows the time relationship of the ROM output signals for line 20, by way of example. In Fig. 4 a indicates the total length of signal from line 20, including the fly-back; b shows the extent of the bottle base image along line 20 (for other lines this may be longer or shorter); c shows a mask signal M which corresponds with the extent of the bottle base image on this line; d is a short duration pulse called "Sample 1" (equivalent to the time represented by approximately one diode in the line) and timed at the start of the mask signal; e is a pulse "Gate 1" which occurs in a leading zone of the mask signal M, starting at the beginning of the mask signal M and lasting for the time to scan approximately 8 diodes (using a 64 x 64 array: it may be different for other arrays); fis another short duration pulse called "Sample 2" similar to pulse d, but occurs at the end of the Gate 1 pulse; g is a pulse "Gate 2" similar in duration to Gate 1 pulse e but occurs in a trailing zone of a mask signal M, being timed to finish at the end of the mask signal M; and h is a short duration pulse called "Sample 3" similar to pulse fand occurs at the end of "Gate 2" pulse. A further masking pulse, "Frame Mask", which is not shown on Fig. 4 because of its relatively long duration, is also generated. This starts at line 1 2 and continues to line 52 as will be described with reference to Fig. 8.

The first synthesised video signal (Video 1) is composed of a line video signal during the bottle mask signal M followed by a constant level signal derived by sampling and holding the video signal during the "Sample 1" period. This continues to be held until the mask signal M of the next line when it is replaced by a constant level signal derived by sampling and holding the video signal during the "Sample 1" period of the said next line until the mask signal of the next following line, and so on.

Thus, Video 1 (shown in Fig. 5) consists of segments of the original video signal waveform within their respective mask signal periods M joined by constant value signals during the periods H, each derived from a sample obtained from the "Sample 1" period at the beginning of the preceding line.

The second synthesised video signal (Video 2) is derived by integrating the video signal waveform during the Gate 1 period and, during the "Sample 2" period at the end of the Gate 1 period, sampling this value and holding it until a similar signal is sampled from the "Sample 2" period of the next line, and so on.

Thus Video 2 signal shown in Fig. 6 consists of segments S1 of signal each chained together, lasting for the duration of a complete line including the fly-back period, and having values corresponding respectively to the original video values, after integration, of the original video signals during successive Gate 1 pulse periods.

The third synthesised video signal (Video 3) is derived in a similar manner but the integration of the original video signal waveform takes place during each Gate 2 period and is sampled during the following Sample 3 period and held until the Sample 3 period of the next line and consists of a chain of segments S2 of signal as shown in Fig. 7.

Successive signal segments S1 of Video 2, and of segments S2 of Video 3, may be of equal value or decrease or increase depending on whether the successive integrated Gate 1 and Gate 2 signals indicate a change or not in the illuminaton of the corresponding group of diodes.

Thus as the array is scanned raster style over the whole area of the bottle base image the Video 2 signal represents a circular scan of approximately half the outer peripheral zone carried out sequentially in say an anticlockwise direction whilst Video 3 represents a similar circular scan of the other half of the bottle base outer periphery in the opposite direction. See Fig. 8.

The two discontinuities D (Fig. 8) in the two part-circular scans are masked out by the Frame Mask signal shown. The Video 1 signal (raster scan) provides the information for these masked out areas and approximates to a continuation of the circular scans.

The Video 2 and Video 3 signals are further processed by low pass filtering and differentiation. The final signals represents rates of change of illumination in the outer peripheral zones. Thus if a foreign body locally reduces the illumination in a peripheral zone, the lightto-dark and then dark-to-light transition as the scan passes over the body will result in both a negative and positive going pulse signal, after differentiation, in the respective Video 2 or Video 3 channel. The detection of signals of both polarity on either channel can be made effective in generating reject signals by known combinations of OR gates, inverters and comparators using a fixed reference for the latter.

The Video 1 signal is also further processed by differentiation followed by separate amplification of the positive going and negative going pulses which correspond to the two edges of a foreign body traversed by a scanning line. The time separation of the two pulses is a measure of the size of an object traversed by that scanning line.

Preferably a further circuit is provided which only outputs the second pulse if the first pulse was more than a pre-set time earlier than the second. Control of this pre-set time is available to the operator of the machine and is used to adjust the sensitivity of the inspection system, i.e. the minimum size of objects it is desired to detect. This form of sensitivity control is very effective and corresponds with the operator's expectations when adjusting the sensitivity. It also ensures that a single light/dark or vice versa transition on any one scanning line will be ignored. Thus a foreign body located right at either end of the line will not be detected on the Video 1 channel.

Similarly, the single transition signal caused by a wedge base of a bottle will not be detectable. The foreign body signal will however be detectable on the Video 2 and Video 3 channels.

Reject signals from all three Video channels and from other detection systems, such as liquid detection, chipped neck detection and opaque bottle base detection, are all combined together with OR gates so that a single bottle rejection mechanism may be used.

The angle of view of the lens system may be increased slightly so that the lower portion of the bottle body may also be imaged on to the array, concentric with and outside the base area. In this case what has been described above as the outer peripheral zone will in fact be this lower side wall area of the body. In this case a further annular zone which is inside and adjacent to the outer zone can be defined with suitable mask signals and two further video signals (e.g. Video 4 and 5 in Fig. 9) be synthesised and processed to inspect what is now the outer base zone.

Claims (14)

1. The method of bottle inspection for the detection of dirt or foreign bodies therein by electronically scanning the bottle base in raster fashion, characterised by synthesising a first video signal containing information from raster scanning the bottle base, synthesising at least one further video signal containing information from at least part of the peripheral zone of the bottle base, and processing the video signals to generate reject signals indicative of the detection of dirt or a foreign body.

2. The method according to claim 1, characterised in that at least two said further video signals are synthesised containing information from diametrically opposite part-circular peripheral zones respectively.

3. The method of bottle inspection for the detection of dirt or foreign bodies therein by electronically scanning the bottle base in raster fashion, characterised by processing the video signal waveform generated by the raster scanning of the bottle base with masking and sampling signals to synthesise at least three video signals containing information relating to the bottle base and at least two segments of annular zones around the periphery of the bottle base, and processing said at least three synthesised video signals to generate a reject signal if any one of said synthesised video signals indicates the presence of dirt or a foreign body in the inspected bottle.

4. The method according to claim 1, 2 or 3, characterised by electronically scanning the bottle base by means of a photo-diode array, of which the individual photo-diodes are arranged in a plurality of lines and are scanned in turn along each line and line-by-line by clock signals, the clock signals also controlling the production of masking and timing signals for each individual line for synthesising and synchronising each of the synthesised video signals, which vary with each line scanned, namely (i) a masking signal which corresponds with the extent of the bottle base image on that line;; (ii) first and second gate pulses which oc cur in the leading and trailing zones respectively of masking signal (i), the first gate pulse starting at the begin ning of the masking signal and lasting for the time to scan a fraction of the diodes in that line and the second gate pulse lasting for a similar period of time and being timed to finish at the end of the masking signal; and (iii) three short duration sampling pulses, respectively, the first sampling pulse being timed at the start of masking signal (i), the second being timed to begin at the end of the first gate pulse (ii), and the third being timed to start at the end of the second gate pulse (ii) of that line, the first synthesised video signal being composed of a line video signal during the masking signal (i) followed by a constant level signal derived by sampling the video signal during the first sampling pulse and holding the sample until the masking signal (i) of the next line when it is replaced by a constant signal derived by sampling the video signal during the first sampling pulse of the said next line and holding it until the masking signal of the next following line, and so on, the second synthesised video signal is derived by integrating the video signal waveform during the first gate pulse, sampling the integrated value during the second sampling pulse and holding it until a similar signal is sampled by the second sampling pulse following the first gate pulse of the next line, and so on, and the third synthesised signal is derived by integrating the video signal waveform during the second gate pulse, sampling the integrated value during the third sampling pulse and holding it until a similar signal is sampled by the third sampling pulse following the second gate pulse in the next line, and so on, the second and third synthesised video signals representing part-circular scans of diametrically opposite peripheral zones carried out in opposite circular directions.

5. The method according to claim 4, characterised by masking out the discontinuities between the part-circular scans by a frame mask signal.

6. The method according to any preceding claim, characterised by differentiating the synthesised video signals, and processing the differentiated signals so that only detection of both positive and negative going pulses corresponding to the two edges of a foreign body is effective to generate a reject signal.

7. The method according to claim 6, characterised by preventing generation of a reject signal if the first pulse occurs more than a pre-set time earlier than the second pulse.

8. The method according to claim 7, characterised by adjusting the sensitivity of the inspection by controlling said pre-set time.

9. The method of bottle inspection for the detection of dirt or foreign bodies therein, substantially as described.

10. Bottle inspection apparatus for detecting dirt or foreign bodies in bottles, comprising means for electronically scanning the bottle base in raster fashion to generate a video signal waveform, means for synthesising a first synthesised video signal by masking from said waveform video signals outside the area of the base to be inspected, means for differentiating the resultant synthesised video signal, and means for processing a differentiated signal which is indicative of the presence of dirt or a foreign body in the inspected bottle to generate a reject signal, means for integrating video signals in leading zones of at least some of the lines of said synthesised video signal to generate a first series of integrated signals, means for integrating video signals in terminal zones of at least some of the lines of said synthesised video signal to generate a second series of integrates signals, means for synthesising from said first and second series of integrated signals respectively, second and third synthesised video signals containing information representing changes in each series of integrated signals of said leading and terminal zones, means for differentiating said second synthesised video signal, means for processing a differentiated signal of said second synthesised video signal to generate a reject signal when the rate of change thereof exceeds a predetermined value, means for differentiating said third synthesised video signal, means for processing a differentiated signal of said third synthesised video signal to generate a reject signal when the rate of change thereof exceeds a predetermined value, and means combining the reject signals generated from said three synthesised video signals.

11. Apparatus according to claim 10, using a raster scanned photodiode array, and means for processing the video signal waveform from the array in combination with mask signals and sampled-and-held or integrated portions of the waveform to synthesise the three video signals.

12. Apparatus according to claim 10 or 11, including means for processing the differentiated signals so that only the detection of both positive and negative going pulses corresponding to the two edges of a foreign body generates a reject signal.

1 3. Apparatus according to claim 12, and comprising means for setting the maximum time period between the positive and negative going pulses for the generation of a reject signal.

14. Bottle inspection apparatus for detecting dirt or foreign bodies in bottles, substantially as described with reference to the drawings.