WO2007095946A1

WO2007095946A1 - Equipment and method for detection of presence of an existence on or in the surface of an item conveyed by a conveyor

Info

Publication number: WO2007095946A1
Application number: PCT/DK2007/000080
Authority: WO
Inventors: Per Arnmark; Claus Borggaard; Jens Michael Carstensen; Niels Christian Krieger Lassen
Original assignee: Slagteriernes Forskningsinstitut
Priority date: 2006-02-22
Filing date: 2007-02-20
Publication date: 2007-08-30

Abstract

Equipment for detecting presence of an existence on or in the surface of an item conveyed by a conveyor (1), which equipment comprises an electronic camera (3) for taking a plurality of pictures of the item conveyed by the conveyor, and a lighting device (4), where the lighting device is adapted to during a first taking to illuminate the surface of the item with light of a first, predetermined colour, during a second taking illuminates the surface of the item with light of a second, predetermined colour, and during possible further takings illuminates the surface of the item with light of one or more further, predetermined colours, and that the equipment comprises a calculating unit for data processing at least two of the pictures taken of the item with illuminations of different colour, and to perform an examination of the achieved data for presence of an existence on or in the surface of the item.

Description

Equipment and method for detection of presence of an existence on or in the surface of an item conveyed by a conveyor

The present invention relates to equipment and a method for detection of presence of an existence on or in the surface of an item conveyed by a conveyor. The equipment comprises an electronic camera for taking a plurality of pictures of the item conveyed by the conveyor, and a lighting device.

Processing of carcasses and parts thereof at slaughterhouses is increasingly auto- mated to improve the products and increase the efficiency. By automation repetitive strain injury is further avoided, and a significant improvement in hygiene is achieved. Tripartition of half pig carcasses into foreend, middle and ham is one of the processes, which has been automated. Hooking of these parts on Christmas trees or processing of the parts are processes, which have been automated in re- cent years. Prior to the automation the operators have till then been able to perform the inspection of the products in conjunction with the manual processing of the products. One of the inspections is to examine if an intersected abscess should exceptionally be present on the cut surface of e.g. middles, which necessitates removal of the product and cleaning of the equipment and conveyor. Now this inspec- tion cannot be performed with the same effectiveness any more, and therefore there can be an increased risk of bacterial contamination of the equipment and conveyor of the line.

The basis for the present invention is hence the need to provide a device to auto- matically detect the presence of an existence on or in a surface of an item conveyed by a conveyor.

Within the field of slaughterhouses and meat processing, it is known to inspect meat and meat product by taking an electronic picture and data-process the picture to find the areas of meat and fat. These methods cannot find meat-like existences in meat, as they cannot distinguish these from the meat.

WO 95/21375 describes a system for checking the quality of pieces of meat on a conveyor. The system comprises a light source placed above the conveyor, a CCD- camera and picture processing equipment. The light source emits mainly broad spectred light and the camera takes one picture of the piece of meat, and the picture is stored as three individual pictures for red, green and blue light, respectively. Picture processing comprises comparison of stored picture values with a table of accepted values. However this system will not be able to detect a presence of e.g. an abscess, as the system will not be able to distinguish an abscess from meat because of the broad-spectred pictures.

WO 02/063939 relates to a process and a system for detection of contamination on e.g. poultry carcasses in a slaughterhouse, where the carcasses are illuminated with broad-spectred light. This system employs a camera with a wavelength separating prism to split the broad-spectred light entering the camera in a plurality of independent optical channels. The camera comprises a plurality of CCD-detectors, each provided with individual filters and supplied with light from the independent optical channels, so that the camera simultaneously takes a plurality of pictures for different wavelenghts. The system comprises further data processing devices, which by means of various algoritms. This system is complicated and expensive, especially because of the many filters, and because it is necessary with several CCD- detectors.

It is an object of the invention to provide a simple and inexpensive system for detection of a presence of an existence on or in the surface of an item conveyed by a conveyor.

This object is met by the invention in that the lighting device is adapted to during a first taking to illuminate the surface of the item with light of a first, predetermined colour, during a second taking illuminates the surface of the item with light of a second, predetermined colour, and during posible further takings illuminates the item with light of one or more further, predetermined colours, and that the device comprises a calculation unit for data processing at least two of the pictures taken of the item with the illuminations in different colour, and to carry out an analysis of the data obtained for presence of an existence at or in the surface of the item. The device according to the invention provides automated inspection of parts, so that e.g. the presence of an intersected abscess on the cut surface of a part can be detected with high certainty, also even if the part is conveyed by a conveyor with the usual high speed of transport for cutting lines at slaughterhouses. The device ac- cording to the invention can in the event of a discovered abscess existence automatically give the alarm to an operator, so that the product can be removed and equipment and conveyor can be cleaned.

Advantageous embodiments of the equipment according to the invention are stated in claims 2-13.

The lighting device can comprise monochrome light sources, so that pictures taken at predetermined wavelenghts are provided, said wavelengths having a bearing on the existence of the particular type of tissue, or which e.g. is adapted to suppress or remove irrelevant existences. The band width of the light from these light sources can be 5-20 nm and is preferably maximum 50 nm. By application of monochrome light the takings are targeted and interfering influence from irrelevant existences, which give reflections outside the wavelength range considered, are avoided.

The lighting device can comprise different types of light-emitting diodes, where each type of diode emits monochrome light of a colour, which is different from the light of the other types. Light-emitting diodes are suited for giving an intense light in the short time which the taking lasts, e.g. 1-10 ms.

The lighting device can comprise 3-8 different light sources or groups of light sources, each emitting light of its own, predetermined colour. It is advantageous to take more than two pictures, as the material can be interpreted more precisely with respect to the particular existence. The number of pictures necessary to take depends on the particular type of tissue and the desired precision in detection.

The lighting device can comprise at least three different light sources or groups of light sources emitting red, green and blue light, respectively. The reflections from the cut surface of a piece of meat are different by these colours of illumination, de- pending on whether it is fat, meat or something else, e.g. abscess tissue, whereby the pictures can be used for suppressing irrelevant types of tissue or highlight the type of tissue searched for.

The lighting device can comprise a light source or a group of light sources emitting amber or orange coloured light, preferably in the wavelength range around 590 nm, and a light source or a group of light sources emitting red light, preferably in the wavelength range around 617 nm. It has turned out to be advantageous by detection of abscess tissue to provide takings at these two colours of light.

The camera and the lighting device can be positioned in a housing. In this way the camera and light sources are protected against fouling. Further the light from the light sources are directed solely towards the area from which pictures of the item is to be taken, when the item is in position within the field of vision of the camera.

The equipment can be constructed in that way that the housing is an oblong box, that the lighting device and the camera is positioned at one end wall of the box, where at least a part of the optical axis of the camera extends in the longitudinal direction of the box, and that the box has an opening allowing taking of pictures of an item present opposite the opening of the box. The housing is oblong as it is advantageous to have a certain distance from the lens of the camera to the item to avoid strong distortions.

The box can house a tilted mirror in the end remote from the lighting device, and have an opening in one longitudinal wall opposite the mirror surface. In this way the cross-distance of the box is reduced, as the optical path is tilted by means of the mirror. In this way it is for example rendered possible to position the box between two conveyors transporting parts from a cutting facility for pig carcasses.

The box may be adapted to give a diffuse illumination of the surface of the item, e.g. in that it is white-matted internally, and in that the lighting device is provided with a frosted glass plate in front of the light sources. Preferably the equipment comprises a calculation unit for data processing at least two of the pictures taken by the equipment with illumination of different colour and for carrying out an examination of the gained data for presence of the existence on or in the surface of the item. The calculation unit can be computer connected to the necessary external units for providing at least two pictures of each item transported past the field of vision of the camera, and which comprises a program for carrying out the necessary analysis of the pictures with a view to detecting the particular type of tissue, and which further may comprise programmes and signal outputs for external units, such as an alarm and/or a monitor.

According to an embodiment the equipment may further comprise an alarm device for automatically give an alarm signal by positive result of the examination.

According to another embodiment the equipment may comprise a monitor, on which a picture of the item can be shown. The picture is preferably a data processed and/or composite picture. When pictures are taken with red, green and blue illumination, respectively, a faithfull reproduction can be formed on the monitor, and this reproduction can be used by an operator to evaluate if there is in fact an existence of the tissue type searched for, or whether there are conditions of the picture which renders it possible to cancel the alarm. The program performing the detection can be designed so that there are relatively many false alarms. These then have to be examined by the operator called by the alarm. Thereby fewer items with actual particular existences can escape the automatic control, which in particular is important by examination for abscess tissue. Even by a number of false alarms it can be rela- tively seldom that the operator is called. The monitor can be adapted to show data processed pictures, in false colours or in true colours, from which the operator from a remote workplace can evaluate if the alarm is false or true.

The equipment can be connected to a physical trigger device for the camera to de- tect the item moved by the conveyor and for actuating taking of two or more pictures when the item is in the field of vision of the camera, e.g. after a predetermined conveying distance from the detection. Other constructions are also possible, where the equipment is not connected to a physical trigger device, but e.g. successively takes pictures, analyzes these for their contents and chooses suitable pictures for further analysis for presence of searched tissue type.

The invention further provides a method for detection of presence of an existence on or in the surface of an item, which is transported by a conveyor, where the method comprises that an electronic camera takes to or more pictures of the surface of the item, while the conveyor moves the item.

The method according to the invention is characterized in that a lighting device illu- minates the surface of the item with light of a first, predetermined colour during the first taking of the surface of the item, with light of a second, predetermined colour during the second taking, and with light of a one or more further, predetermined colours during possible further takings, and that a calculation unit performs a data processing of at least two of the pictures taken of the item, and perform an exami- nation of the achieved data for presence of the existence on or in the surface.

Preferred embodiments of the method according to the invention appears from claims 14-20.

Even though the invention here is described mainly in relation to detection of presence of abscess tissue in cut carcasses, it can also be used for other purposes, e.g. to detect whether there are presences of meat, fat, cartilage or bone on a middle, which should be on the foreend or the ham, e.g. presence of shoulder knuckle or shoulder blade in the cut surface. If such are detected the cutting facility may be corrected in accordance herewith.

The pictures provided by the equipment can in addition to their primary object also be used for other purposes, such as for determination of the meat-fat-ratio in a part or presence of meat or fat at a meat product.

The invention can find application in other fields than cutting of pig carcasses, e.g. within other fields of the meat business and within other businesses than the meat business, in particular by products having natural variations in desired or undesired presences on or in the surface.

The invention will be described further in the following with reference to the drawing, in which - Fig. 1 shows an embodiment of experimental equipment for detection of the presence of a type of tissue on the cutting face of parts transported on a conveyor,

- Fig. 2 shows the equipment from another angle,

- Fig. 3 shows a detail of the equipment, - Fig. 4 shows a principal sketch of an equipment according to the invention,

- Fig. 5. shows a principal sketch of another equipment according to the invention, and

- Fig. 6 shows a processed picture of the cutting face of a piece of meat.

The experimental equipment in Fig. 1 comprises a conveyor 1 for conveying parts, e.g. middles, from an automatic cutting facility dividing half carcasses into three. Next to the conveyor the equipment has a box 2 with measuring devices examining each part passing the box with respect to detecting presence of a certain type of tissue, e.g. an intersected abscess.

At the bottom of the box 2 an electronic black-and-white-camera 3 (Fig. 2), e.g. with a 1/3" or 1/2" CCD or CMOS. Under the camera a lighting device is arranged, said lighting device comprising a frosted plate 4 and a number of light-emitting diodes positioned between the plate and the bottom of the box. The diodes are distributed over the area of the bottom. There are four different types of diodes emitting light of individual colours, such as monochrome light with the following wavelengths: 470 nm (blue), 530 nm (green), 590 nm (orange) and 617 nm (red), respectively. The different types are distributed among each other, so that a uniform and dispersed light from the frosted plate is achieved, when a type of diode is turned on. The walls 5 of the box are painted white, so that the light is diffused. The light is reflected from a tilted mirror 6 at the top of the box and leaves through an opening provided with clear plain glass at the top of the side of the box. The light from the opening falls on the cut surface of a part transported past the window. A lid 7 with a vertical back plate serves together with the sides of the box to screen the lighting device, so that the light will not disturb operators present in the premises. Under the box a compartment with control and calculating unit is situated, said unit serving to control on/off of the light-emitting diodes and to initiate taking of pic- tures of the cut surface and carry out picture processing by means of algorithms.

A guide rail 8 above the conveyor 1 guides an incoming part out to a distance from the window, so that the cut surface of the part will get to lie in the focal plane of the camera. A detector 9 behind the rail 8 detects when the front edge of the part passes in front of the detector. The detector sends a signal to the control and calculating unit to initiate and perform a measuring and calculating process detecting the presence of a possible abscess in the cut surface of the part, when the part has come completely into the field of vision of the camera. During e.g. 20 ms a series of four pictures is taken with illumination from each of the types of diodes. The expo- sure time is for example 1-2 ms, which causes a motional smearing of approximately 1 pixel with a conveyor speed of 500 mm/s. This results in an acceptable picture resolution.

The measuring and calculation process comprises: - The different types of light-emitting diodes are turned on and off successively to give an illumination of the cut surface of a particular wavelength.

- The camera is activated to perform taking of pictures of the cut surface, when a type of diode is turned on, whereby a series of four pictures taken with illumination of the cut surface with light of different discrete wave- lenghts, preferably in the blue, green, yellow and red part of the spectre.

- In the control and calculating unit the pictures are adjusted for perspective distortion and co-registred for compensation of the shifting brought about by the transport of the part between the takings, whereby the individual pixels in the pictures will represent the same part of the cut surface of the part. - The adjusted pictures are processed, e.g. the red picture can be subtracted from the orange picture, a new picture can be generated where each pixel value is found from the distance of corresponding pixels in the colour picure from a defined abscess colour (statistically weighted) and/or areas of a par- ticular light value and/or of a certain size/shape is highlighted.

- The pictures are analyzed by means of suitable algorithms to find possible areas with abscess tissue.

- Information is sent to an operator, e.g. on a monitor, which can show proc- essed/analyzed/composite (colour) pictures.

- An alarm signal from an optical/acustic alarm device is activated by the control and calculating unit if the analysis shows presence of abscess tissue.

By activation of the alarm dvice the operator can immediately by means of the moni- tor evaluate whether the alarm is false or true, and he does not have to move to the equipment or inspect the part. If false the alarm is cancelled, if true the part is removed. By true alarm the operator initiates a cleaning process for equipment and conveyor having been in contact with the part. An alarm, which is approved true, will rarely happen, but will ensure the hygiene.

Unlike the method used today, in which it for example is the hanging operator performing the examination, the present equipment saves cleaning of conveyors and processing equipment placed downstream to the measuring equipment, e.g. down to where the parts are hanged on Christmas trees or even further, if automatic equipment for hanging is used. In the present equipment the part can be removed immediately after it has left the equipment, as soon as it has been detected, without contamination of downstream conveyors and machines.

On the other side of the conveyor similar equipment can be arranged to inspect the opposite cut surface of the middle. All the three parts (foreend, middle and ham) formed at the cutting may by means of two such measuring equipment be examined for abscesses in the cut surfaces.

The sketch in Fig. 4 shows the principle in an equipment of the construction shown in Fig. 1. A part 10, e.g. a middle, is conveyed on a conveyor 11, and pictures of the cut surface 10a of the part are taken by means of an electronic camera 13 positioned in a box 12. The cut surface is illuminated by means of a lighting device 14 arranged at the bottom of the box, and which device comprises different types of light-emitting diodes with individual colours. The device has a frosted glass plate positioned in front of the diodes for dispersing the light. The light is reflected by a mirror 16 and exits through an opening in the box equipped with a protective glass to the cut surface of the part. The illumination is approximate diffused. The detector, the guide rail and the control and calculating unit is not shown in fig. 4, but is part of the equipment.

The inclining lines in Fig. 4 show the limitation of the field of vision. The box may as an example have a depth of 350 mm and a heigth of 625. The optical distance from the camera lens to the focal plane is e.g. 625 mm. The field of vision is e.g. 500x400 mm.

Fig. 5 shows a sketch similar to the one of Fig. 4, but of equipment, in which no mirror is used for tilting the optical path. The box is here e.g. 450 mm deep, which can complicate position of it between to conveyors transporting parts from a cutting facility.

The picture in Fig. 6 is achieved by comparison of the spectres to find out how far the colour of a pixel is from the colour of a standard abscess, e.g. how close the spectre of a given pixel is to an established standard spectrum for abscess tissue, calculated according to Mahalanobis method. The abscess appears dark or black, and is denoted by 20.

Claims

1. Equipment for detecting presence of an existence on or in the surface of an item conveyed by a conveyor (1), which equipment comprises: - an electronic camera (3) for taking a plurality of pictures of the item conveyed by the conveyor, a lighting device (4), characterized in that the lighting device is adapted to during a first taking to illuminate the surface of the item with light of a first, predetermined colour, during a second taking illuminates the surface of the item with light of a sec- ond, predetermined colour, and during possible further takings illuminates the surface of the item with light of a one or more further, predetermined colours, and that the equipment comprises a calculation unit to data process at least two of the pictures taken of the item with illumination of different colour and to perform an examination of the achieved data for presence of the existence on or in the surface of the item.

2. Equipment according to claim 1 , characterized in that the lighting device (4) comprises monochrome light sources.

3. Equipment according to claim 1, characterized in that the lighting device (4) comprises different types of light-emitting diodes, where each type of diode emits monochrome light of a colour, which is different from the light of the other types.

4. Equipment according to claim 1 , characterized in that the lighting device (4) comprises 3-8 different light sources or groups of light sources emitting light of individual, predetermined colours.

5. Equipment according to claim 1 , characterized in that the lighting device (4) comprises at least three different light sources or groups of light sources emitting red, green and blue light, respectively.

6. Equipment according to claim 1 , characterized in that the lighting device (4) comprises a light source or group of light sources emitting amber or orange col- oured light, preferably in the wavelength field around 590 nm.

7. Equipment according to claim 1 , characterized in that the lighting device (4) comprises a light source or group of light sources emitting red light, preferably in the wavelength field around 617 nm.

8. Equipment according to claim 1, characterized in that the camera (3) and the lighting device (4) is positioned in a housing (2).

9. Equipment according to claim 8, characterized in that the housing (2) is an oblong box, that the lighting device (4) and the camera (3) is positioned at one end- wall, whereby at least a part of the optical axis of the camera extends in the longitudinal direction of the box, and that the box has an opening allowing taking of pictures of an item present opposite the opening of the box.

10. Equipment according to claim 9, characterized in that the box contains a tilted mirror (6) at the end remote from the lighting device (4) and has an opening in one longitudinal wall opposite the mirror face.

11. Equipment according to claim 8, characterized in that the housing (2) is adapted to give diffuse illumination of the surface of the item.

12. Equipment according to claim 11 , characterized in that it comprises an alarm device for automatically giving an alarm signal by positive result of the examination.

13. Equipment according to claim 10, characterized in that it comprises a monitor on which a picture of the item can be shown.

14. Method for detecting presence of an existence on or in the surface of an item conveyed by a conveyor (1), which method comprises,

- that an electronic camera (3) takes two or more pictures of the surface of the item while the conveyor (1 ) moves the item, characterized in - that a lighting device (4) illuminates the surface of the item with light of a first, predetermined colour during the first taking of the surface of the item, with light of a second, predetermined colour during the second taking of the surface of the item, and with light of one or more additional, predetermined 5 colours during possible further takings, and that a calculating unit performs a data processing of at least two of the pictures taken of the item, and performs an examination of the achieved data for presence of the existence on or in the surface.

10 15. Method according to claim 14, characterized in that pictures are taken with 3-8 different illuminations of separate, predetermined colours.

16. Method according to claim 15, characterized in that at least three pictures are taken with red, green and blue illumination, respectively.

15

17. Method according to claim 14, characterized in that the calculating unit automatically gives signal to an alarm by positive result of the examination.

18. Method according to claim 17, characterized in that the data processing com- 0 prises co-registring at least two pictures, whereby the movement of the item between taking of the pictures is compensated, so that the individual pixels are corresponding with regard to the surface part which the represent.

19. Method according to claim 14, characterized in that the examination of the 5 data material comprises detection of pixel clusters with light values having a number within a given range.

20. Method according to claim 17, characterized in that an operator confirms or cancels the alarm by evaluating a picture on a monitor, on which a picture of the 0 item is shown.