WO2024013671A1

WO2024013671A1 - Plant and a method for inspecting products

Info

Publication number: WO2024013671A1
Application number: PCT/IB2023/057144
Authority: WO
Inventors: Alessio MANGHI; Claudio Quarantelli
Original assignee: Raytec Vision S.P.A.
Priority date: 2022-07-15
Filing date: 2023-07-12
Publication date: 2024-01-18

Abstract

Inspection plant for inspecting products comprising: i) a conveying line (2) for conveying products; ii) inspection means (3) for inspecting products in transit along the conveying line (2); said inspection means (3) comprising: X-ray emitting means (31) and dual energy x-ray detection means (32); at least a part of the conveying line (2) being operatively interposed between said X-ray emitting means (31) and said X-ray detection means (32); The detection means (32) comprise: - an electronic board (320) comprising a first and a second face (321, 322) that are turned in opposite directions; the first face (321) being turned towards the X-ray emitting means (31); - a first photodiode (323) obtained on the first face (321); - a second photodiode (324) obtained on the second face (322); - a scintillator (325) facing the second photodiode (324). The first photodiode (323) defines an X-ray detector having a lower energy level than those intended to be detected by a detector group (327) comprising the second photodiode (324) and the scintillator (325); one scintillator is absent at the first photodiode (323).

Description

DESCRIPTION

PLANT AND A METHOD FOR INSPECTING PRODUCTS Technical field

The present invention relates to an inspection plant for inspecting products, in particular but not exclusively food products. Purely by way of non-limiting example, the food products could be plants, fruits, vegetables, etc.

Background art

Inspection plants are known which analyse the shape, colour, size of the food products so as to identify those that do not comply with the preset standards.

In this regard, it is known to use vision systems that acquire images of the food products flowing along an underlying conveying line and, by means of sophisticated algorithms, are able to understand the compliance or not of the product.

X-ray sensors are also known for detecting a shape of an object and used for example to inspect closed suitcases in airports or at the entrance to high-security areas. This is to identify and prevent the access of weapons, explosives, etc. Such x-ray sensors comprise an x-ray emitter and an x-ray receiving system; they thereby allow to outline the shape of the object. Dual energy sensors are also known in which there is a first sensor to detect higher energy X-rays and a second sensor to detect lower energy X-rays. It is thereby possible to improve the contrast of the image of the detected shape and to have more information related to the density and/or other properties of the material of which the object under examination is constituted.

In particular, dual energy X-ray receivers are known which are provided with an electronic board comprising a printed circuit having a first and a second face. The first face is turned towards the x-ray emitter, the second face is turned towards the opposite direction. A first photodiode extends starting from the first face and moving away from the board; a second photodiode extends starting from the second face and moving away from the board. The first and the second photodiode extend aligned along the same direction. The first photodiode has an end which is spaced from the board covered by a first scintillator. The second photodiode has an end which is spaced from the board covered by a second scintillator. The scintillators, if struck by X-rays, emit a light pulse that is then detected by the photodiode to which they are associated. To detect two different energy ranges, the scintillators are different in composition and/or thickness. When described with reference to the first and the second photodiode, it can be advantageously repeated for a plurality of pairs of photodiodes which then come to define a specific array.

A drawback of such a solution is that it is difficult to detect low energies because they are attenuated or absorbed by the scintillator. A further drawback is related to the fact that the scintillator causes scattering and thus reduces accuracy.

Disclosure of the invention

In this context, the technical task underlying the present invention is to propose an inspection plant and a method for inspecting products which allows to optimise the 'dual energy' operation and to improve sensor accuracy.

The defined technical task and the specified aims are substantially achieved by an inspection plant and a method for inspecting products, comprising the technical features set forth in one or more of the appended claims.

Brief description of drawings

Further features and advantages of the present invention will become more apparent from the approximate and thus non-limiting description of a preferred, but not exclusive, embodiment of an inspection plant and a method for inspecting products, as illustrated in the accompanying drawings, in which:

- figure 1 shows an inspection plant according to the present invention; - figure 2 shows a detail of a component of the inspection plant of figure 1 ;

- figure 3 shows a schematic view of such a component.

Detailed description of preferred embodiments of the invention

In the appended figures, reference numeral 1 denotes a plant for inspecting products, in particular food products, for example but not limited to plants, vegetables, fruits. The plant is more generally usable for products to be selected in which there is a detectable difference in attenuation of the transmitted energy spectra.

The inspection plant 1 comprises a conveying line 2 for conveying products. The conveying line 2 may for example comprise a movable solid support, such as a conveyor belt. Such a conveying could also occur in another manner: in aerial suspension, in a liquid stream, etc.

The inspection plant 1 may comprise an inspection means 3 for inspecting products in transit along the conveying line 2. The inspection means 3 comprises X-ray emitting means 31. Such an emitting means 31 is well known in the technical field and therefore not further described. The emitting means 31 comprises X-ray detection means 32. The means 32 is dual energy detection means 32.

The inspection means 3 are substantially stationary. In particular, they do not change orientation with respect to the conveying line.

At least one part of the conveying line 2 is operatively interposed between said X-ray emitting means 31 and said X-ray detection means 32. In particular, at least one part of the conveying line 2 transits between the emitting means 31 and the detection means 32. Suitably the emitting means 31 and the detection means 32 lie one above and the other below a same part of the conveying line 2.

The detection means 32 comprises an electronic board 320. It is a substantially two-dimensional element. Advantageously, the board 320 has a thickness less than 2 millimetres. Such an electronic board 320 comprises a printed circuit. It is also known as a PCB.

The electronic board 320 comprises a first and a second face 321 , 322 that are turned in opposite directions. Suitably they are flat faces. The printed circuit board is obtained at least in part on the first and on the second face 321 , 322. The first face 321 faces the X-ray emitting means 31 . Suitably the first face 321 faces the conveying line 2. The first face 321 intercepts the x-rays before the second face 322.

The detection means 32 comprises a first photodiode 323 obtained on the first face 321.

The detection means 32 comprises a second photodiode 324 obtained on the second face 322.

Conveniently, the first and second photodiodes 323, 324 are of the same type. In particular, the first and second photodiodes 323, 324 are identical to each other.A scintillator 325 faces the second photodiode 324. Such a scintillator 325, if struck by X-rays, generates a light signal detectable by the second photodiode 324. Preferably, such a signal is not detectable by the first photodiode 323 (they are located on two opposite sides of the electronic board 320). The fact that the scintillator 325 faces the second photodiode 324 makes it possible to optimise the signal detection. In fact, the second photodiode 324 is thereby struck by the light emitted by the portion of the scintillator facing it without signal losses due to the absorption of the latter.

The first and the second photodiode 323, 324 connect to the electronic board 320 at two points that are located in the same position, but on opposite faces of the board 320. A line orthogonal to the board 320 suitably intersects such two points. The first and the second photodiode 323, 324 extend longitudinally along opposite directions and a same direction away from the board 320.

Conveniently, the first and second photodiodes 323, 324 protrude away from the board 320 by less than 5 millimetres.

Suitably, the first and the second photodiode 323, 324 extend along a same line away from the board 320.

The first photodiode 323 defines an X-ray detector with a lower energy level than those intended to be detected by a detector group 327 comprising the second photodiode 324 and the scintillator 325. The first photodiode 323 therefore allows to detect X-rays with a lower energy level than those detected by the second photodiode 324 with the aid of the scintillator 325.

A scintillator 325 is absent at the first photodiode 323. Therefore, no scintillator faces or is in contact with the first photodiode 323. In particular, no scintillator faces the first face 321 or is located interposed between the board 320 and the emitting means 31 .

The first photodiode 323 is therefore not operatively associated with a scintillator. In fact, the first photodiode 323 performs a direct conversion of the X-rays into an electrical pulse. The Applicant has verified that such a direct conversion typically occurs with X-rays at lower energy levels. In particular, the first photodiode (which suitably is/comprises a silicon junction PN) allows to directly convert low-energy photons (below 50 keV, preferably below 30 keV) into electrons while being insensitive to higher energies.

Suitably, the first photodiode 323 may comprise silicon that generates an electrical signal if struck by X-rays (although the choice of silicon is advantageous, it is not necessary since there are also other materials that allow this).

In a particular embodiment, the scintillator 325 is spaced apart from the second photodiode 324. Therefore, the scintillator 325 and the second photodiode 324 are not in direct contact with each other. Suitably, there is a space occupied by ambient air between the scintillator 325 and the second photodiode 324.

In an alternative embodiment, the scintillator 325 is in direct contact with the second photodiode 324. In particular, they are in contact with each other. Suitably, the scintillator 325 adheres to an end of the second photodiode 324. The scintillator 325 and the second photodiode 324 are suitably glued to each other. If necessary, the second photodiode 324 and the scintillator 325 can be mutually supported on each other (without gluing or other constraint).

Suitably, the scintillator 325 may be interposed between the second photodiode 324 and a reflective surface 328 (e.g., a mirror).

Since the material with which the scintillator 325 is composed can be traversed in part by photons of visible light (such as the light it emits by itself) and its thickness usually being reduced, the aforementioned expedient allows the intensity of the emitted light to be further increased. Most of the photons emitted from the surface of the scintillator 325 turned towards the reflective surface 328 are then projected backward in the direction of the second photodiode 324 which detects the high energies.

Advantageously, the scintillator 325 is removable with respect to the second photodiode 324 and the electronic board 320. This facilitates periodic maintenance, being able to intervene on a specific component.

In fact, all the electronic components that are continuously affected by ionizing electromagnetic waves, such as X-rays, deteriorate over a period of time and must be replaced; the advantage of having as irradiated parts, and therefore deteriorable, only the photodiodes and the scintillator, minimises the number of components to be replaced and makes the repair of the entire sensor easy and economical; moreover, since the scintillator part is removable, it can be decided whether to replace only the 'exhausted' parts (scintillator, photodiodes or both), therefore the possibility of being able to further reduce the repair costs is granted.

Suitably, the first photodiode 323, the second photodiode 324 define a modular pair which repeats along the board 320.

In particular, this modular pair is repeated identically along a straight line parallel to the faces of the board 320.

The use of a modular structure allows to change the length of the sensitive line on a case-by-case basis without having to make specific hardware changes.

Suitably, a scintillator can be associated with the second photodiode of each modular pair. Suitably, there is a scintillator for each pair. The modular pairs can be arranged according to any geometry: single or adjacent rows, matrix, arbitrary shape.

In such a case, the first photodiode 323, the second photodiode 324, and the scintillator 325 associated with the second photodiode 324 define a modular set of three which repeats along the board 320.

If necessary, the set of scintillators can be a single piece or several elements in succession.

In particular, the first photodiodes form at least a first row in combination. Similarly, all of the second photodiodes form a row or rows in combination. Similarly, the scintillators form one or more rows in combination. Suitably, one or more of the features described for the first photodiode 323 may be repeated for all the first photodiodes. Suitably, one or more features described for the second photodiode may be repeated for all the second photodiodes. Suitably, one or more features described for the scintillator 325 may be repeated for all the scintillators. In particular, all the scintillators are located in the same half-space relative to a plane on which the board 320 lies (and identified by the substantially two-dimensional board 320).

Summarising, in a particular exemplary embodiment the inspection plant comprises a first and a second row of photodiodes on opposite faces of a single PCB (printed circuit). The two rows are perfectly superimposed on the two faces. The row of photodiodes in the upper part will be left without a scintillator, thus exposed directly to the X-rays, the lower row will have a scintillator layer capable of emitting visible light. This scintillator is placed as close as possible to the photodiode (if possible attached and glued), the photodiode will thus detect the light emitted by the scintillator in the upper part thereof, i.e. , the part most exposed to the X-rays.

Advantageously, the electronic board 320 comprises filtering means 326. The filtering means 326 filters a part of the X-rays and allows the transit of a part of the X-rays. The filtering means 326 selectively attenuates some X-rays. The filtering means 326 can therefore be defined as means for selectively attenuating the X-rays. Copper, which is normally used in the construction of PCBs, significantly attenuates the intensity of the photons selectively. The filtering means 326 acts as a barrier to the X-rays having a first energy range. The X-rays having a second energy range overcome such a barrier and can be intercepted by the scintillator 325. The X-rays overcoming the filtering means 326 have a higher energy level and can therefore be intercepted by the scintillator 325. Suitably, the filtering means 326 is made of a metal material. Suitably, the means 326 comprises a layer interposed between the first and the second face 321 , 322. Such a layer is preferably made of a metal material, advantageously comprising copper or an alloy thereof.

In a particular solution, the first photodiode 323 could be replaced more generally with a first element for the direct conversion of X-rays. The second photodiode 324 could be replaced with another photodetector element.

An object of the present invention is also a sorting plant 10 for sorting products. Such a sorting plant 10 comprises an inspection plant 1 having one or more of the features described above.

The sorting plant 10 further comprises means 11 for removing products from the conveying line 2 on the basis of information from the detection means 32. The removal means could be of various kinds: for example, the product to be removed could be intercepted and diverted by a mechanical element, a fluid jet, etc.

A further object of the present invention is a method for inspecting products, for example, but not limited to, food products. Such a method is advantageously implemented by an inspection plant 1 having one or more of the features described above.

The method conveniently comprises the steps of: i) letting products transit along a conveying line 2; advantageously the products are advanced along a solid support, such as a conveyor belt; ii) emitting, through emitting means 31 , X-rays towards said products transiting along a section of the conveying line 2; iii) intercepting, through detection means 32, the X-rays emitted by the emitting means 31 ; this occurs after the X-rays have crossed the conveying line 2 (and therefore have been able to intercept a part of the products).

The step of intercepting the X-rays comprises the sub-steps of:

- detecting through a first photodiode 323 a part of the X-rays;

- detecting through a scintillator 325 and a second photodiode 324 that is associated with the scintillator 325 a part of the X-rays having an energy level greater than that of the X-rays detected by the first photodiode 323.

The second photodiode 324 is therefore a photodiode that intercepts higher energy X-rays and the first photodiode 323 intercepts the lower energy X-rays.

The first and the second photodiode 323, 324 are applied to a first and a second face 321 , 322 of an electronic board 320, respectively.

As already mentioned above, the first and the second face 321 , 322 are turned in opposite directions. The first face 321 is suitably turned towards the emitting means 31. The X-rays cross the board 320 from the first face 321 towards the second face 322.

The first photodiode 323 performs a direct conversion of the X-rays into an electrical pulse without using a scintillator 325.

The second photodiode 324 instead detects the light emitted by the scintillator 325 when the latter is struck by the X-rays.

As already mentioned above, by crossing the board 320, the X-rays are at least partially filtered by a filtering layer present in the board 320. Therefore, the second photodiode 324 will be struck by X-rays having a higher energy. Therefore, the second photodiode 324 can detect higher energy X-rays.

The present invention achieves important advantages. Firstly, it allows to obtain a solution in which the components are optimised and at the same time allows to improve the detection of low energies because the absence of a scintillator at the first photodiode does not attenuate them. Furthermore, the absence of the scintillator in such an area reduces the scattering phenomenon.

The invention as it is conceived is susceptible to numerous modifications and variants, all falling within the scope of the inventive concept characterised thereby. Further, all the details can be replaced with other technically equivalent elements. In practice, all the materials used, as well as the dimensions, can be any whatsoever, according to need.

Claims

1 . An inspection plant for inspecting products comprising: i) a conveying line (2) for conveying products; ii) inspection means (3) for inspecting products in transit along the conveying line (2); said inspection means (3) comprising: X-ray emitting means (31 ) and dual energy x-ray detection means (32); at least a part of the conveying line (2) being operatively interposed between said X-ray emitting means (31 ) and said X-ray detection means (32); said detection means (32) comprising:

- an electronic board (320) comprising a first and a second face (321 , 322) that are turned in opposite directions; the first face (321 ) being turned towards the X-ray emitting means (31 ); said electronic board (320) comprising filtering means (326) of at least a part of the X-ray;

- a first photodiode (323) obtained on the first face (321);

- a second photodiode (324) obtained on the second face (322);

- a scintillator (325) facing the second photodiode (324); characterised in that one scintillator is absent at the first photodiode (323).

2. The plant according to claim 1 , characterised in that said first photodiode (323) comprises silicon that generates an electrical signal if struck by X-rays.

3. The plant according to claim 1 or 2, characterised in that the scintillator (325) is spaced from the second photodiode (324).

4. The plant according to any one of the preceding claims, characterised in that the filtering means (326) act as a barrier for the X-rays that have a first energy range; the X-rays that have a second energy range overcoming said barrier and being able to be intercepted by the scintillator (325).

5. The plant according to any one of the preceding claims, characterised in that the scintillator (325) is removable with respect to the second photodiode (324) and to the electronic board (320).

6. The plant according to any one of the preceding claims, characterised in that the first photodiode (323) and the second photodiode (324) define a modular pair that is repeated along the board (320).

7. The plant according to any one of the preceding claims, characterised in that it comprises a plurality of photodiodes applied to said first face (321 ) and not operatively associated with a scintillator.

8. The plant according to any one of the preceding claims, characterised in that the scintillator (325) can be interposed between the second photodiode (324) and a reflective surface (328).

9. A plant for sorting products comprising:

-an inspection system (1 ) according to any one of claims 1 to 8;

- means (11 ) for removing products from the conveying line (2) on the basis of information from the detection means (32).

10. A method for inspecting products comprising the steps of: i) letting products transit along a conveying line (2); ii) emitting, through emitting means (31 ), X-rays towards said products transiting along a section of the conveying line (2); iii) intercepting through detection means (32) said X-rays, after the X-rays have intercepted a part of the products; step iii) comprising the sub-steps of:

- detecting through a first photodiode (323) a part of the X-rays;

-detecting through a scintillator (325) and a second photodiode (324) that is associated with the scintillator (325) a part of the X-rays having an energy level greater than that of the X-rays detected by the first photodiode (323); the first and second photodiodes (323, 324) being applied respectively to a first and a second face (321 , 322) of an electronic board (320), the first and the second face (321 , 322) being turned in opposite directions, the first face (321 ) being turned towards the emitting means (31 ); characterised in that the first photodiode (323) performs a direct conversion of the X-rays into an electrical pulse without using a scintillator (325).