WO2004105967A1

WO2004105967A1 - Imaging device

Info

Publication number: WO2004105967A1
Application number: PCT/NL2004/000380
Authority: WO
Inventors: Servaes Joordens; Robert Peters; Poppo Jan Wit
Original assignee: Fps Food Processing Systems B.V.
Priority date: 2003-05-27
Filing date: 2004-05-27
Publication date: 2004-12-09
Also published as: CL2004001298A1

Abstract

A device for imaging products (P) conveyed on a conveyor track, such as fruit or eggs, comprising: conveying means moved by the conveyor track, on which the products (P) are conveyed according to at least one row formed in advance and can rotate during this conveyance; lighting elements provided in a housing, for lighting, over a well-defined path, the surfaces of each product from the row of products; a camera (4) device provided in a housing, for recording an image of each lighted product (P); a system of mirrors (10, 20, 30, 40) provided in the housing, with mirrors on both sides of the row, parallel to and symmetrical with respect to the row, and at an angle with a vertical plane through the row, wherein the optical path lengths of all beams coming from the products and directed by the mirrors (10, 20, 30, 40) towards the camera device are equal; and an image processing device for processing the images obtained by the camera device into a flow of image data wherein at least a part of the image data are compared to preset image properties, wherein, by means of the system of mirrors, on each side of the row, at least one single beam is led from the products to a single camera, wherein the image of a single product is composed of at least three surface strips.

Description

Title: Imaging device

The present invention relates to a device according to the preamble of claim 1.

Such a device is known from NL1013375, also of applicant. This describes in which manner the components from which the device has been assembled need to be positioned to be able to compose images of the products, which enable reliable sorting of the products. More in particular, in this arrangement, it was decided to image surface parts near the bearing parts of the products on the conveyor rollers, with the mirrors being placed directly next to the rollers. However, it has been found that the mirrors thus arranged quickly become soiled. Applicant has also sought to obviate this drawback, as described in WO00/27550. Although, with such a device, the mirrors can adequately be kept clean, it cannot prevent the regular occurrence of hitches resulting from conveyance of too large products or non-singled products, for instance two smaller products which have still ended up in a single nest formed by two successive rollers so that the products get stuck between the mirrors.

A further problem is that, when constructing the beams, not only optical path lengths should be taken into account, but also the possibility of providing sorting rows next to one another, and, consequently, avoiding the crossing and, accordingly, covering of parts of beams.

The device according to the present invention has solved above-mentioned problems and is, for this purpose, characterized in that, by means of the system of mirrors, on each side of the row, two beams are led from the product to a single camera, while the image of a single product is composed of at least three surface strips. By means of the arrangement according to the invention, it is achieved that sorting of products of various sizes is possible without needing to adjust the sorting device for this. Further, a simplification is achieved in that the cleaning device can be omitted. Further embodiments of the present invention are characterized in that the angles of the beams coming directly from the products are evenly distributed over the two quadrants, formed by the vertical through the row, and located above the row, in particular that the angles in these quadrants are between 5° and 185°, more particularly that the two angles furthest apart are preferably in the range of 70° to 45° with the vertical. According to a further characteristic, the invention is characterized in that, for each beam, at least two mirrors are used.

In order for the proper light source comprising the needed spectrum part to be sufficient in the simplified mirror arrangement, the device is further characterized in that the lighting elements are metal vapor lamps which are provided symmetrically with respect to the row and the vertical plane, more particularly that the lamps are substantially tubular and are cased in a cylindrical casing transmitting the lighting which is at least partly flown through by a cooling fluid likewise transmitting the lighting. In a further embodiment of the invention, the lamps are directed substantially parallel to the beams which are directed at the two angles furthest apart.

In another advantageous embodiment of the invention, the mirrors are mounted on plates of which the two ends are connected, by means of a mortise and tenon clamped joint, with the two end plates, downstream and upstream, of the housing. Such a fixation ensures a reliable and reproducible operation of the device according to the invention.

More in particular, the tenon comprises a middle part, with a recess in the middle thereof, and with two edge ends with bends perpendicular to the middle part in the same direction, with the tenon being clampingly provided in a mortise in an end plate of the housing, with the recess over a cam-shaped curvature of a corresponding middle part of the mortise, and with the bends against contact edges on both sides of the middle part of this mortise. Further details of the device according to the invention will be elucidated with reference to a drawing, in which:

Fig. 1 diagrammatically shows, for a first exemplary embodiment, the positioning of camera, mirrors and products for a single row;

Fig. 2 diagrammatically shows a situation for four rows next to one another utilizing the exemplary embodiment according to Fig. 1;

Figs. 3A and 3B diagrammatically show two further exemplary embodiments;

Fig. 4 shows a perspective view of a housing for the device according to the invention; and Fig. 5 shows a detail of the attachment of parts of the device according to the invention.

In the different Figures, like parts are numbered alike. Fig. 1 diagrammatically shows a vertical cross section of a frame 1 in which the device according to the invention has been included, with the frame resting on a support of a sorting device (not drawn). Such sorting devices are generally known, for instance from EP687508. In such a device, products P, for instance apples, are between two hourglass-shaped rollers, with successive rollers forming a row and these rollers being connected with an endless chain of a conveyor. Fig. 1 shows, for a first exemplary embodiment, a cross section, namely perpendicular to a single row. V represents a vertical plane through such a row. In Fig. 1, plane V is a plane of symmetry. An important part of the frame 1 is formed by a horizontal bridge 2, with a vertical column 3 thereon. In this column, a camera 4 and support means for a number of mirrors of a system of mirrors are included. In order to be able to see products P which pass below the camera 4 from all sides, in other words, in order to make images of the whole surface, in the present exemplary embodiment, from four sides, beams from the surface of a rotating product are projected on the focal plane of the camera 4. Of these four beams, two are on one side and two are on the other side of the plane of symmetry V, symmetrically with respect to V. On the one side, these are, in cross section, a first beam 100, 100', 100", and a second beam 200, 200', 200", and on the other side a first beam which is only designated by reference numeral 101 and which is symmetrical to the first beam on the one side, and a second beam with only reference numeral 201 which is symmetrical to the second beam on the one side.

The Figure shows how, on the one side, the first beam 100, successively via mirrors 10 and 20, and the second beam, via mirrors 30 and 40, find their way to the camera 4. For the other side, for beam 101, the symmetrically arranged mirrors 11 and 21 are used for the first beam, and the symmetrically arranged mirrors 31 and 41 for the second beam. By way of illustration, for some mirrors, mirror holders are shown, namely mirror holder 5 for mirror 10, and mirror holder 6 for mirror 30. As the Figure shows, further mirror holders are accommodated in the column 3. Further, dotted lines indicate the center lines of all beams.

The angles which the beams make with the vertical plane V are shown between the dotted lines and the drawn vertical line representing plane V. These are chosen such that the beams coming directly from the products P divide the quadrant as equally as possible, taking into account the above drawbacks. In Fig. 1, the angle for the first beam 100 is approximately 50° and for the second beam 200 approximately 10°.

It will be clear to any skilled person that, by the combination of rotation, translation, that is, the progress of the conveyor, and the beam angle, an image of the whole surface of a product P is obtained. The flow of image data thus obtained is processed in a computer. More in particular, data on colors and positions are obtained. In the case of fruits such as apples, these data will be translated into presence of blossom ends, stem ends and damages or other undesired fruit skin characteristics. For sorting purposes, at least parts of this flow of data may be compared to preset image properties. This enables sorting according to color, damages, or even shape.

The length of the mirrors, reckoned in the direction parallel to the conveyor direction which is equal to the direction of the row, is chosen in a suitable manner, taking into account the above-mentioned parameters and the size of the fruits.

Lighting elements are not shown in the present Fig. 1. It can be noted about these that they make an angle with the vertical such that the products are lighted on all sides as optimally as possible. Because the frame 1 is generally accommodated in a case or box-shaped housing, or, alternatively, forms a part thereof, the angles are chosen for this purpose, more particularly approximately at the height of the beams with the largest angles. Unlike in many known devices according to the state of the art, where, usually, strip lights are used in combination with infrared lamps, in the device according to the invention, halogen vapor lamps or metal vapor lamps have been chosen, for instance mercury vapor lamps of the firm of OSRAM. These have both the advantages of compactness and the broad spectrum emitted by these lamps.

In particular, for tubes, cylindrical casings for cooling can be used. In an advantageous manner, these are close-fitting cylinders transmitting the lighting which are at least partly flown through by a cooling fluid likewise transmitting the lighting, such as water.

The lighting may further be provided with polarization filters, depending on the colors and properties of the surfaces of the products.

In addition, extra infrared lamps may be used, so that, accordingly, a suitable camera, or cameras, need(s) to be chosen to be used. Further, it needs to be noted that, at the height of the horizontal bridge 2, a transparent screening may be provided to further prevent pollution of the system of mirrors.

Fig. 2 shows an arrangement for multiple rows. In order to save space on the sides of the frame, mirror 10 has been divided into a system of two mirrors 10' and 10".

Figs. 3A and 3B show further exemplary embodiments, in the manner as shown in Fig. 1, in which three beams are used to image surface strips. Again, the optical path lengths are equal. Such configurations may also be used for multiple rows next to one another. The differences with the first exemplary embodiment can be accounted for by different guiding, also called "folding", of the light beams in order to thus obtain more advantageous layouts of rows next to one another.

By means of the above-described arrangements, images will be obtained of three of four surface strips of a product. These strips will generally be contiguous to one another such that they allow the imaging of the whole surface of a product P.

Fig. 4 shows a view of a housing in more detail, with frame 1 itself forming part of the housing. It will be clear to any skilled person that a different choice may also be made for this. However, when the frame 1 has been placed in a housing, this will generally require more space . T designates the conveying direction of the products, and 50 designates a part of a conveying device by means of which the products P are conveyed. In more detail, end plates 51, 51' are shown, upstream and downstream, as well as plates 52 on which the mirrors have been mounted. Ends of these plates are provided in mortises 60 in the end plates 51, 51' shown. Fig. 5 shows a detail of an end of a plate 52 inserted into a mortise 60. The mortise 60 consists of a middle part 61, drawn horizontally here, connecting two end mortise parts 63, 63'. Along one of the edges of the middle part 61, a small curvature, bulge or cam 62 has been provided. It will be clear that such a mortise 60 is usually provided in plate metal to thus ensure stiffness and rigidity. The end of the plate 52 provided in such a mortise 60 can be considered a tenon inserted into the mortise. At least the end or the tenon also has a middle part 70, a recess 71 therein, and two ends 73, 73' bent perpendicularly towards the same side at bends 72. The dimensions have been chosen such that, for inserting, a clamped joint is required, with recess 71 resting on cam 62, and with tenon parts located next to the bends being clampingly in contact with edges or contact edges near the end mortise parts 63, 63' of the mortise. This clamping enables a very robust mounting which offers a great rigidity during operation of such a conveying device. This ensures a very reliable and reproducible operation of the device according to the invention.

It will be clear to any skilled person that small modifications in the above-described device are understood to fall within the scope of the appended claims. For instance, the lighting elements and the camera devices may also be clampingly mounted by means of the mortise and tenon joints.

Claims

1. A device for imaging products conveyed on a conveyor track, such as fruit or eggs, comprising: conveying means moved by the conveyor track, on which the products are conveyed according to at least one row formed in advance and can rotate during this conveyance; lighting elements provided in a housing, for lighting the surfaces of each product from the row of products over a well-defined path; a camera device provided in the housing, for recording an image of each lighted product; - a system of mirrors provided in the housing, with mirrors on both sides of the row, parallel to and symmetrical with respect to the row, and at an angle with a vertical plane through the row, wherein the optical path - lengths of all beams coming from the products and directed by the mirrors towards the camera device are equal; and - an image processing device for processing the images obtained by the camera device into a flow of image data wherein at least a part of the image data are compared to preset image properties, characterized in that, by means of the system of mirrors, on each side of the row, at least one single beam is led from the products to a single camera, wherein the image of a single product is composed of at least three surface strips.

2. A device according to claim 1, characterized in that the angles of the beams coming directly from the products are evenly distributed over the two quadrants, formed by the vertical and the horizontal through the row, and located above the row.

3. A device according to claim 2, characterized in that the angles in the said quadrants are between 5° and 185°.

4. A device according to claim 3, characterized in that the two angles furthest apart are preferably in the range of 70° to 45° with the vertical.

5. A device according to any one of the preceding claims, characterized in that for each beam at least two mirrors are used.

6. A device according to any one of the preceding claims, characterized in that the lighting elements are metal vapor lamps which are provided symmetrically with respect to the row and the vertical plane.

7. A device according to claim 6, characterized in that the lamps are directed substantially parallel to the said beams which are directed at the two angles furthest apart.

8. A device according to claim 6, characterized in that the lamps are substantially tubular and are cased in a cylindrical casing transmitting the Hghting which is at least partly flown through by cooling fluid likewise transmitting the lighting.

9. A device according to any one of the preceding claims, characterized in that the mirrors are mounted on plates of which the two ends are connected, by means of a mortise and tenon clamped joint, with the two end plates, downstream and upstream, of the housing.

10. A device according to claim 9, characterized in that the tenon comprises a middle part, with a recess in the middle thereof, and with two edge ends with bends perpendicular to said middle part in the same direction, wherein the tenon is clampingly provided in a mortise in an end plate of the housing, with the recess over a cam-shaped curvature of a corresponding middle part of the mortise, and with the bends against contact edges on both sides of the middle part of the said mortise.