GB2226130A

GB2226130A - Scanning system

Info

Publication number: GB2226130A
Application number: GB8923336A
Authority: GB
Inventors: Firouz Pouya
Original assignee: GIFFORD ENGINEERING Ltd
Current assignee: GIFFORD ENGINEERING Ltd
Priority date: 1988-10-17
Filing date: 1989-10-17
Publication date: 1990-06-20
Also published as: GB8824258D0; GB8923336D0

Abstract

A scanning system is for detecting articles e.g. eggs 11 on a conveyor 10. Eggs 11 pass below a light source 14 and light from the eggs 11 is reflected to a video camera 15. The video camera 15 scans the conveyor transverse to its direction of movement 13 a plurality of times within each of a series of bands spaced a predetermined distance apart. The band width has to be sufficiently wide to distinguish gaps between touching eggs 11 and narrow enough to minimise the chances of rescanning the same egg 11 within the previous band or the next band. The scanning system may be used in an egg counter. Alternatively, it may be used to detect holes in sheets in a laundry. <IMAGE>

Description

SCANNING SYSTEM The present invention relates to a system for scanning objects so as to determine their number or condition.

The present invention is particularly, but not exclusively, concerned with the counting of eggs. It is normal practice to count eggs produced by a farm prior to grading or farm packing of those eggs. Although many counting systems have been proposed, all suffer from various inaccuracies. When it is considered that the number of eggs passing through the counter per day may be of the order of 100,000 or more, it can be seen that even a 1% error represents a large number of miscounted eggs.

Therefore, the present invention has been devised primarily to provide a more accurate method of counting eggs.

In essence, the present invention proposes that the eggs are scanned by a light detector as they are moved along e.g. a conveyor, so that the amount of light reflected will indicate the presence or absence of an egg at any point along the scan. Systems which produce such a scan have already been devised, but it has been found that, a single scan produces inaccuracies. In particular, if the line of the scan happens to coincide with the point where two adjacent eggs meet, then the scan will not necessarily detect the change from one egg to the other, and a miscount will occur. Therefore, the present invention proposes that the light detector carries out a multiplicity of scans, to define a band of scanning.This band should be wide enough to detect where two adjacent eggs meets, because there will be at least some "gap" between the eggs enclosed within the band.

Where the eggs travel along a conveyor, the bands of scanning will normally be transverse to the conveyor, and spaced by predetermined distances along the conveyor.

Existing types of egg conveyors generally support the eggs on a series of bars transverse to the direction of movement of the conveyor, and the spacing of those bars then assists the spacing of the scanning bands, since an egg will normally be supported on two adjacent bars, and the scanning band will therefore pass approximately midway between each two adjacent bars. At first sight, the bands of scanning should be as wide as possible, since then they will detect more easily the places where two eggs meet (since more "gap" will be included within the band).

However, if the band is made too wide, it may overlap the end of an egg which has already been scanned in the previous band, or will be scanned in the next band, thereby again causing a miscount. There is thus a balance to be struck between narrow bands, with the risk of undercounting, and wide bands with the risk of overcounting.

Preferably, the light detector is a video camera arranged to scan a single line only. Then, as the eggs move on the conveyor belt below the camera, activation of the camera and its associated signal processing circuitry for a predetermined length of time causes a multiplicity of scans to be made, which define a band relative to the eggs because of the movement of the conveyor. The amount of light detected is then converted to an electrical signal, which is processed by the processing circuitry to determine the number of eggs from the number of changes in light level detected by the camera within each band. To produce a suitable signal for the detector, it is preferred that light be sone onto the eggs, which is then reflected to the camera.There should then desirably be a dark background immediately below the eggs, to maximise the difference in signal across the edge of an egg.

An embodiment of the invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a general perspective view of an embodiment of a scanning system according to the present invention; Fig. 2 shows a sectional view through the system of Fig. 1 in the direction of movement of the conveyor; Fig. 3 shows a plan view of a part of the conveyor of Fig. 1; Figs. 4a to 4c show signals corresponding to different egg configurations; and Fig. 5 shows a block diagram of a processing circuit for analysing the signal from the detector in the system of Fig. 1.

As shown in Figs. 1 and 2, a conveyor 10 supports a plurality of eggs 11 thereon. The conveyor 10 illustrated in Fig. 1 has a plurality of bars 12 spaced at equal intervals. and the eggs 11 rest on the bars. The conveyor 10 moves the eggs in a direction of arrow 13 below a light source 14 (e.g. consisting of a strip light 14a and a reflector 14b), and light from the light source 14 is reflected from the eggs to a video camera 15 which scans in a line transverse to the arrow 13. A dark backing material 16 is provided below the conveyor 10 (seen clearest in Fig.

2) so that there is a contrast between the eggs and that background. A bar detector 17 is provided adjacent the conveyor 10, which detects the passage of the bars 12. In dependence on the intervals between the passage of those bars 12 and the bar detector 17, the camera 15 and its associated processing circuitry (to be described later) is activated for a series of predetermined intervals, each of which intervals is sufficiently long to enable the camera 15 to carry out a multiplicity of scans. Since the conveyor 10 is moving during those scans, a series of bands are defined.

These bands are shown in Fig. 3 as by dotted lines defining bands 20a,20b,20c.

Consider now the possible signals that may be detected as the camera scans the bands 20a,20b,20c. For a single, isolated, egg such as egg 21a, the signal will simply rise to a axlum, at the edge of the egg, and then fall again to a minimum at the other edge of the egg. The result is that shown in Fig. 4a. When, however, two eggs touch such as shown at eggs 21c,21d, then the problem is to distinguish the gap between them. The resulting signal will be that shown in Fig. 4b, where there is a slight drop in the signal from the camera, but not to the minimum since there is always some part of the eggs within the band in the area where the two eggs meet.The problem here is that there will be inevitable fluctuations in the maximum level of the signal detected, and the processing electronics (to be described in more detail later) must distinguish between the random variations in the "maximum" signal reflected from the egg (i.e. corresponding to the presence of an egg) and the drop in signal due to gaps between eggs, as shown in Fig. 4b.

There is a further problem, namely that a large egg may overlap two or more bands, as shown by egg 21b.

Looking at the signal from band 20c due to eggs 21b and 21e, the result is as shown in Fig. 4c where there is a small hump corresponding to the partial overlap of egg 21b with band 20c, and a larger hump corresponding to the fall overlap due to egg 21e. Again, the processing electronics must be able to distinguish between these two types of humps. At first sight, it seems easy because the smaller hump (from egg 21b) does not reach the maximum signal height X. However, when it is remembered that the maximum signal height will vary from that level X due to variations in reflection from the eggs, the processing electronics must distinguish between a hump which is low due to random effects, and a hump which is low because it corresponds only to a partial overlap of an egg with a scanning band.

Fig. 5 shows the electronic processing system for analysing the output of the camera 15. The signal from the camera 15 is first passed to a filter circuit 30 which deletes from the camera signal all synchronisation and frame pulses which are generated by the camera itself. The resulting signal from the filter circuit then should correspond substantially to the signals shown in Figs. 4a to 4c, with the eggs producing a series of humps in an otherwise low level signal. Although Figs. 4a to 4c show that constant level as zero, in practice, there will be a non-zero base signal.

The signal from the filter circuit 30 is then amplified by an amplifier 31 and passed to a processing circuit 32. This processing circuit 32 analyses the resulting signals. In order to detect the change between one scanning band and another, the processor circuit 32 is connected to the detector 17, so that its analysis may be synchronised with the camera 15. Thus, the processor circuit 32 may analyse the amplified output from the filter circuit 30 as a series of bands as was described with reference to Fig. 3. Indeed, this arrangement does not require tbe detector 17 to control the camera 15, and instead the camera 15 may continuously scan the belt, so that the output from the filter circuit 30 and amplifier circuit 31 to the processor circuit 32 is a continuous record of the scans of the camera.Then, the processor circuit 32 may use the signals from the detector 17 to "chop" the continuous signal from the camera into a series of bands, ignoring the scans that the camera has made in the intervals between the bands.

The microprocessor circuit 32 then analyses the signals to detect the various possible changes in the shape of the humps, as was described with reference to Figs. 4a to 4c. With suitable analysis, accurate measurement of the numbers of eggs can be made, and the processor circuit 32 may then signal the number of eggs counted to an output circuit 33 which may have e.g. a display for displaying the number of eggs. Alternatively, the signal from the processor circuit 32 may be fed direct to another computer system if required.

Although an embodiment of the invention has been described above, the present invention is not limited to this embodiment. For example, although the above description is based on a conveyor with bars to support the eggs, this is not necessary and the eggs could be randomly arranged on a moving conveyor belt. However, it is then more difficult to define the bands of scanning, since the eggs are less regularly arranged than on a conveyor with bars, and hence such a conveyor arrangement is not preferred.

Furthermore, although the present invention has been described with reference to counting of eggs, it is not limited thereto and a scanning system according to the present invention may be used for scanning other objects.

For example, in laundries it is often necessary to detect holes in sheets. By placing the sheets on a dark conveyor belt, and passing them below a suitable light detector, holes will be recorded as changes in level of the detected signal. Again, a suitable detector may enable the scanning to be in a series of bands, each one corresponding to the width of a sheet.

Claims

CLAIMS:

1. A scanner comprising a conveyor for transporting articles, and a detection system for detecting the articles on the conveyor by scanning the conveyor, the detection system comprising a light source for illuminating the conveyor and the articles, a detector for detecting reflected light, and means for analysing variations in the reflected light to detect the articles, wherein the detection system is arranged to define a plurality of spaced apart scanning bands, each of the scanning bands having a multiplicity of scans therein, and the means for analysing the variations is arranged to determine the variation in the reflected light within each scanning band on the basis of a comparison of the multiplicity of scans within each band.

2. A scanner according to claim 1, wherein the light source is fixed and the detector is arranged to scan the conveyor.

3. A scanner according to claim 1 or claim 2, wherein the spacing between the bands is greater than the spacing of the scans within the band.

4. A scanner according to any one of the preceding claims wherein the bands are transverse to the longitudinal length of the conveyor.

5. An article scanner according to any one of the preceding claims wherein the light source comprises a strip light arranged transverse to the longitudinal length of the conveyor

6. A scanner according to any one of the preceding claims wherein the conveyor comprises a series of bars for supporting the articles, and the spacing between the bands is related to the spacing of the bar.

7. A scanner according to any one of the preceding claims wherein the detector comprises a video camera.

8. A scanner substantially as described herein with reference to and as illustrated in Figs. 1 to 5 of the drawings.

9. A method of counting articles comprising transporting articles on a conveyor relative to a detection system, the detection system having a light source illuminating the conveyor and the articles, and a detector detecting reflected light, wherein the detector defines a plurality of spaced apart scanning bands each of the scanning bands having a multiplicity of scans therein, and the variation in the reflected light is analysed to determine the variation in the reflected light within each scanning band on the basis of a comparison of the multiplicity of scans within each band.

10. A method of counting articles substantially as any one herein described with refernce to the accompanying drawings.