WO2004111928A2

WO2004111928A2 - Identifying information on the surface of an article

Info

Publication number: WO2004111928A2
Application number: PCT/GB2004/002541
Authority: WO
Inventors: Peter Michael Hage
Original assignee: Phasor Limited; Littelfuse Limited
Priority date: 2003-06-12
Filing date: 2004-06-11
Publication date: 2004-12-23
Also published as: GB2402796B; WO2004111928A3; GB2402796A; TW200511142A; GB0313488D0

Abstract

A device (10) for identifying information on the surface of an article, for example a fuse (24), is described and has an article locator (12) for holding the fuse to be identified. Device (10) is also provided with a plurality of image producing cameras (26), each separated by 120°, which are aimed at a fuse (24) which is located within the lighting area (28). The images are processed and compared within an image comparator, which uses a pattern matching algorithm to identify the closest matched pattern and gives a correlation for the images produced by the other camera which activates an accept/reject trigger (30).

Description

A method and device for identifying information on the surface of an article

The present invention relates to a method and device for identifying information on the surface of an article, and particularly, but not exclusively, to a method and device for identifying information on the surface of an article, specifically for checking information written on an external surface of a fuse.

It is of particular importance that during the manufacture, transportation and installation of fuses that the correct fuse can be identified, that batches of different fuses, do not become mixed, that mixed fuses can be separated and that fuses carrying erroneous end caps can be identified and rejected.

Where fuses are installed within equipment during manufacture, the fuses normally are not colour coded or printed with an ampage rating or with other information, ^' as is the case for domestic fuses. Typically, these fuses have their ampage rating stamped on an end cap. It is also often the case that the other end cap is stamped with approval certification marks indicating which national standards agencies have approved the fuse for use and thus allowed their approvals rating mark to be applied .

It is possible to stamp this information on the flat end surface of the end cap. However, this has the disadvantage that the area available for stamping is then quite limited when compared to the circumferential area available on the curved surface. Furthermore, the stamping of the flat end surface may- interfere with the solder connection between the end cap and the fuse wire.

When the ratings and approval information is stamped on the curved side of the end cap the information thereon proves very difficult to read. It is important that both false positive and false negative readings of the information are avoided. This is particularly the case for the ratings where it is vital that the correctly rated fuse is put into the correct position in a manufactured article. If an incorrect fuse is used there is a risk that the fuse's ampage rating will be too low and the fuse will blow immediately on use of the article, or that the fuse's rating will be too high and that in the event of an electrical fault within the device, the fuse will not blow.

Fuses can be checked by eye. However, a fuse is typically two centimetres in length and the end caps around 5 millimetres in length. In some instances fuses are provided with further end caps to which wires are attached, in order that they may be easily inserted into a circuit board, thereby forming a so- called "pigtail fuse". In this instance, it is important that the ratings and approval information is located on the central- most portion of the original end cap of the fuse and as a result, it is not unusual for the information stamped onto the fuse end cap to be only two millimetres in height. Therefore manual inspection would generally require magnification. Even with such magnification the time required to check a large number of fuses is significant and the rate of false positives (accepted fuses carrying incorrect information) and false negatives (rejected fuses carrying the correct information) remains unacceptably high.

Apparatus allowing the mechanisation of this process has been previously developed. The technique used involves locating the end cap of a fuse adjacent a line camera and rotating the fuse along its axis, or rotating a scanning head around a fixed fuse, so that the line camera is able to produce a two-dimensional image on the circumference of the end cap. This image is then interpreted by character recognition software in a computer to recognise the characters thereon. This method has the disadvantage that the necessary rotation of the fuse slows the process considerably and requires a mechanism to grip and rotate the fuse. Furthermore, the character recognition requires considerable computer power which further slows the process and requires a high specification computer to run the apparatus at an acceptable speed.

. Preferred embodiments of the present invention seek to overcome the above described disadvantages of the prior art.

According to an aspect of the present invention there is provided a method of identifying information on a surface of an article, the method comprising: -

(I) recording at least one first image of at least part of an article from each of a first plurality of directions;

(ii) comparing each said first image with a plurality of second images of a reference article recorded from a second plurality of directions; and (iii) determining for each said first image whether a match exists, within predetermined limits, between said first image and a said second image.

By recording a plurality of images from a plurality of cameras, the advantage is provided that it is not necessary to rotate the article, typically a fuse, and therefore the holding mechanism can be simpler, and similarly it is not necessary to rotate the camera around the fuse. As a result of . the use of static cameras the time required to obtain images of the fuse is significantly less. Existing methods of testing fuses have not exceeded 1 fuse tested per second, whereas the present invention can process fuses at the rate of 3 or 4 a second. Furthermore, because the image is recognised by selection from a plurality of previously stored reference (second) images the advantage is provided that the processing time required in order to recognise the information is reduced. As result, the method can be run at a higher speed without loss of accuracy. The present invention also provides the advantage that when new characters are added to the fuse, for example, a new approvals stamp, it is not necessary to programme this into the character recognition software. In order to introduce a previously unknown fuse it is merely necessary to insert the fuse into the device and produce the multiplicity of second images . From then on, fuses can be tested to this reference.

In a preferred embodiment the method further comprises the step of determining, for a plurality of matched pairs of said first and second images, whether the angular separation between the directions from which a pair of said first images were taken is substantially the same as the angular separation between the directions from which the corresponding said second images were taken. By also checking that the difference between the angles of the cameras of the first images and the angles through which the second images have been rotated correspond, the advantage is provided that this adds a double check to the method.

The article may comprise an electrical fuse, and the surface of the article may comprise a surface of an end cap of said fuse.

In a preferred embodiment the method may further comprise the step of accepting or rejecting the article according to the degree of match between said first and second images.

According to another aspect of the present invention, there is provided an apparatus for identifying information on a surface of an article, the apparatus comprising :-

(I) imaging means for recording at least one first image of at least part of an article from each of a first plurality of directions;

(ii) comparator, means for comparing each said first image with a plurality of second images of a reference article recorded from a second plurality of directions; and

(iii) matching means for determining for each said first image whether a match exists, within predetermined limits, between said first image and a said second image.

In a preferred embodiment the apparatus may further comprise determining means for determining, for a plurality of matched pairs of said first and second images, whether the angular separation between the directions from which a pair of said first images were taken is substantially the same as the angular separation between the directions from which the corresponding said second images were taken.

In another preferred embodiment the apparatus may also further comprise display means for displaying said degree of match.

In a further preferred embodiment the apparatus may further comprise separator means for separating articles into first and second groups in response to said matching means.

(I) at least one imager for recording at least one first image of at least part of an article from each of a first plurality of directions;

(ii) at least one comparator for comparing at least one said first image with a plurality of second images of a reference article recorded from a second plurality of directions; and

(iii) at least one matching device for determining for at least one said first image whether a match exists, within predetermined limits, between said first image and a said second image.

In a preferred embodiment the apparatus may further comprise at least one determining device for determining, for a plurality of matched pairs of said first and second images, whether the angular separation between the directions from which a pair of said first images were taken is substantially the same as the angular separation between the directions from which the corresponding said second images were taken.

In another preferred embodiment the apparatus may also further comprise at least one display device for displaying said degree of match.

In a further preferred embodiment the apparatus may further comprise at least one separator device for separating articles into first and second groups in response to at least one said matching device.

According to a further aspect of the present invention there is provided an article transporting apparatus comprising : -

at least one holding member adapted to rotate about a respective axis and having at least one recess adjacent a periphery thereof for supporting a respective article;

at least one flexible belt for engaging at least one said holding member for holding at least one article in position in a respective said recess;

a plurality of guide members for supporting the or each said belt; and

drive means for causing rotation of the or each said holding member about the corresponding said axis. In a preferred embodiment said drive means comprises at least one device apparatus adapted to drive said holding member or said guide members.

In another preferred embodiment at least one said flexible belt comprises at least one elastomeric material.

Preferred embodiments of the present invention will now be described, by way of example only, and not in any limitative sense, with reference to the accompanying drawings in which: -

Figure 1 is a side view of a device of the present invention;

Figure 2 is a sectional view of a portion of a device of the present invention;

Figures 3 and 4 are examples of the images produced as part of the present invention; and

Figure 5 -is a schematic representation of the- method of the present invention.

Referring to Figures 1 and 2, a device 10 for identifying information on the surface of an article has an article locator 12 for holding an article to be identified. The article locator has a disc 14 mounted on an axle 16 and having recesses 18 around the edge of the disc. The article locator also has a band 20, typically made of an elasticated polymer, mounted on guide wheels 22. Band 20 also engages disc 14 so as to hold articles, typically fuses, 24 in recesses 18. Device 10 is also provided with a plurality, in this instance 3, image producing cameras 26. Each camera 26 is separated by 120° and is aimed at a fuse 24 which is located within the lighting area 28.

The images are processed and compared within an image comparator (not shown) , which uses a pattern matching algorithm to identify the closest matched pattern and gives a correlation expressed as a percentage. This percentage correlation may be displayed on a screen (also not shown) or may activate an accept/reject trigger 30 which causes a fuse 24 to either fall down a reject shoot 32 or an accept shoot (not shown) . Fuses 24 are located in recesses 18 by pneumatic insertion devices 34.

Referring to Figures 3 and 4 in which are shown examples of the first images produced by cameras 26. Three first images 36a, 36b and 36c are produced which show the fuse 24. From these images it is possible to see the end caps 38, end cap 38a carrying ratings information and end cap 38b carrying approvals stamps .

When a new fuse is introduced to be tested, a reference fuse is inserted into device 10. An image is then taken by each of the cameras 26. The fuse is then rotated through 10° and a further three images taken. This rotation of 10° and producing of images is repeated until twelve images have been produced by each camera. This therefore produces a series of 36 images which represent the fuse rotated through 360° in 10° steps. This selection of 36 images represents the second images.

Once the second images are stored it is possible to compare this reference fuse with test fuses. A fuse 24 is introduced into recesses 18 by pneumatic insertion devices 34 and are held in position by band 20. Disc 14 rotates so as to move fuse 24 into lighting area 28. If disc 14 is driven guide wheels 22 freely rotate and are not driven in order that the fuses remain in recesses 18 as band 22 is free to rotate in direction R¹ whilst disc 14 rotates in direction R². When fuse 24 is located within lighting area 28 three first images 36a, 36b and 36c are taken, at step Sl of Figure 5. One of these first images, typically 36a, is compared using a pattern matching algorithm with the database of second images, at step S2, in an attempt to find a match. If no match is found at step S2, the fuse is rejected. If a match is found, the first image 36b, taken by the next camera is then compared with the second images in the database. First image 36b is compared with all of the second images in the database. If no match is found the fuse is rejected. An additional check may be added at this time by checking that the angle between the cameras which produced first images 36a and 36b is the same as the angle between the second images matched with these first images, in this instance 120° or 12 second images further on. - If a further first image, i.e. 36c, is available, step S3 is repeated. Once all first images- have been compared and matched the fuse may be accepted.

Whether a match is found is determined by a pattern matching algorithm which produces a correlation expressed in a percentage, and maybe displayed on a screen and/or may trigger the accept/reject trigger 30.

An alternative checking method is the match the first image 36a with a second image as described above. If a match is found first image 36b is then compared with the second image which is 120° (or 12 images) away from the second image matched to 36a. If the correlation percentage is sufficiently high a match is found and the step is repeated for 36c, otherwise the fuse is rejected.

These techniques can be used to check both ends of the fuse at once thereby typically checking the rating and approvals information at one time. This technique will also detect (and reject) fuses with two identical end caps.

This method can also be used to check for other defects in a fuse such as a blob of solder being stuck to the outside of the fuse.

Furthermore, the technique may check internal features of a transparent fuse such as fuse integrity.

It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only, and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.

For example an additional may be added where no match is found between a first image and any of the second images. This might entail comparing the first images with other collections of second images in order to see if the fuse is of another known type. As a result a more complex trigger mechanism could be used to sort the fuses.

Claims

1. A method of identifying information on a surface of an article, the method comprising :-

(ii) comparing each said first image with a plurality of second images of a reference article recorded from a second plurality of directions; and

(iii) determining for each said first image whether a match exists, within predetermined limits, between said first image and a said second image.

2. A method according to claim 1, further comprising the step of determining, for a plurality of matched pairs of said first and second images, whether the angular separation between the directions from which a pair of said first images were taken is s-ubstantially the same as the angular separation between the directions from which the corresponding said second images were taken.

3. A method according to any one of the preceding claims, wherein the article comprises an electrical fuse.

4. A method according to claim 3, wherein the surface of the article comprises a surface of an end cap of said fuse.

5. A method according to any one of the preceding claims, further comprising the step of accepting or rejecting the article according to the degree of match between said first and second images.

6. A method of identifying information on a surface of an article, the method substantially as hereinbefore described with reference to the accompanying drawings .

7. An apparatus for identifying information on a surface of an article, the apparatus comprising: -

(ii) comparator means for comparing each said first image with a plurality of second images of a reference article recorded from a second plurality of directions; and

8. An apparatus according to claim 7, further comprising determining means for determining, for a plurality of matched pairs of said first and second images, whether the angular separation between the directions from which a pair of said first images were taken is substantially the same as the angular separation between the directions from which the corresponding said second images were taken.

9. An apparatus according to claim 7 or 8, further comprising display means for displaying said degree of match.

10. An apparatus according to any of claims 7 to 9, further comprising separator means for separating articles into first and second groups in response to said matching means .

11. An apparatus for identifying information on a surface of an article, the apparatus comprising: -

12. An apparatus according to claim 11, further comprising at least one determining device for determining, for a plurality of matched pairs of said first and second images, whether the angular separation between the directions from which a pair of said first images were taken is substantially -the same as the angular separation between the directions from which the corresponding said second images were taken.

13. An apparatus according to claim 11 or 12, further comprising at least one display device for displaying said degree of match.

14. An apparatus according to any of claims 11 to 13, further comprising at least one separator device for separating articles into first and second groups in response to at least one said matching device.

15. An apparatus for identifying information on the surface of an article, the apparatus substantially as hereinbefore described with reference to the accompanying drawings.

16. An article transporting apparatus comprising :-

a plurality of guide members for supporting the or each said belt; and

drive means for causing rotation of the or each said holding member about the corresponding said axis.

17. An apparatus according to claim 16, wherein said drive means comprises at least one device apparatus adapted to drive said holding member or said guide members.

18. An apparatus according to claim 16 or 17, wherein at least one said flexible belt comprises at least one elastomeric material .

19. An article transporting apparatus substantially as hereinbefore described with reference to figures 1 and 2 of the accompanying drawings .