WO2010008303A1

WO2010008303A1 - Improved method and apparatus for article inspection

Info

Publication number: WO2010008303A1
Application number: PCT/NZ2009/000140
Authority: WO
Inventors: Gadi Ben-Tal
Original assignee: Anzpac Systems Limited
Priority date: 2008-07-15
Filing date: 2009-07-13
Publication date: 2010-01-21

Abstract

Means and methods for inspecting the surface(s) of an article inside an inspection zone wherein the light source(s) used to illuminate the article is configured to produce a light beam that is directed to be offset from the article such that the beam axis does not impinge on the article to reduce the effects of light spots. The invention has particular application to the detection of features on the surface of fruit, vegetables or other articles for grading purposes.

Description

IMPROVED METHOD AND APPARATUS FOR ARTICLE INSPECTION

FIELD OF THE INVENTION

The invention relates to a method and apparatus for inspecting the surface of articles and in particular, but not exclusively to a method and apparatus for the surface inspection and subsequent grading of articles, in particular fruit, although the invention has wider application.

BACKGROUND

Processing lines for articles such as fruit often require different quality articles to be separated. This is an important commercial function, which may be used for example, to distinguish between fruit destined for export and fruit destined for the local market. Manually grading articles is costly, slow and prone to inaccuracies. Thus, automated methods and apparatus for grading articles have been developed. Known sorters can. grade and sort produce by weight, colour, blemish, dimension, shape, density, internal taste/quality etc.

The use of one or more video cameras is one known method of automatically sensing characteristics of articles. For example, the method and apparatus described in United States Patent No. 4,825,068, the disclosure of which is incorporated herein by reference, uses a video camera in conjunction with mirrors to obtain a picture of each article as it travels past the line of sight of the mirrors. The mirrors enable a larger portion of the article, which is typically generally spherically shaped, to be simultaneously viewed by the camera.

WO 03/23455, assigned to the assignee of the present invention and incorporated herein by reference, describes an article inspection apparatus configured to allow substantially the entire surface of an article to be inspected. The apparatus includes a conveyor which rotates the article to be inspected as it passes through an inspection site. The article is viewed by an imaging system having first and second cameras and a mirror arrangement that defines the field of view of the cameras. The imaging system is arranged so that the first camera has a field of view including a top view and a first upper side view of the article and the second camera has a field of view including a top view and a second upper side view of the article. Lighting is provided which substantially uniformly lights the article. As described in WO 03/23455, sorting systems may have a single lane through which articles are processed, or may have multiple lanes which operate in parallel. As would be apparent to those skilled in the art, the degree of integration or use of common parts for multiple-lane sorters may be varied without invention, depending on the desired characteristics thereof (e.g. considerations such as size/weight/cost of the equipment, the degree of modularity, resistance to breakdown by reducing critical components etc).

Computers and software may be used to analyse multiple images of pieces of fruit and use this to sort it into different operator defined classifications based on, for example, the fruit's surface colour, diameter, shape, presence of blemishes etc. Algorithms may be provided to track, record and save blemish (and other) details, which are used to grade the articles.

Inspection systems relying on optical detection require the article to be lit. Variations in lighting over the surface of the article can lead to incorrect detection of surface characteristics, particularly when analysing colour, as it becomes difficult to distinguish between bright patches caused by lighting and lighter coloured patches on the article itself. For articles having reflective surfaces, these problems are more pronounced. Moreover, when using focused light beams as a light source, reflection spots may be created that are detected as blemishes on the article or they may mask actual blemishes. One solution to this problem is to use a diffused light source but such light sources are not ideally suited for use in detecting punctures or holes in an article, which is important for many types of articles, particularly fruit.

It is an object of the present invention to provide an improved inspection apparatus or method, and / or a lighting arrangement therefor.

Alternatively, it is an object at least to ameliorate one or more of the aforementioned problems in article inspection.

Alternatively, it is an object of the invention at least to provide the public with a useful choice.

Other objects of the present invention may become apparent from the following description. Throughout this specification, any reference to items of prior art is in no way to be deemed as an admission that such prior art constitutes part of the common general knowledge.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a lighting arrangement for an inspection apparatus, the inspection apparatus including an imaging system for capturing at least one image of the surface of an article when the article is inside an inspection zone, the lighting arrangement including: one or more light sources configured to illuminate said article so as to at least reduce reflection spots in the captured image(s), wherein a first said light source is configured to produce a first light beam having a first predetermined angular beam width about a first beam axis and arranged such that it illuminates at least a portion of the article inside the inspection zone with the first beam axis offset from the article so it does not impinge thereon at least when the article is inside the inspection zone, and/or wherein a second said light source is configured to produce a second light beam having a second predetermined angular beam width about a second beam axis and arranged such that it illuminates at least a portion of the article inside the inspection zone with the second beam axis incident on the article but orientated such that the axis of light reflected off the article from the second light source is directed other than at the imaging system, and more particularly, an image capture means thereof.

Preferably, the first and/or second beam width is between 5° and 30°, more preferably between 10° and 25°, and most preferably, between 15° and 20°.

Preferably, the first predetermined angular beam width is substantially the same as the second predetermined angular beam width.

Thus, according to preferred embodiments, the light sources are configured to produce directional light. While particular angles have been provided and are preferred, the invention is not limited thereto. Preferably, the first and/or second beam axis is offset by between 30° and 60°, more preferably between 40° and 50°, and most preferably, is substantially equal to 45° from vertical.

According to preferred embodiments, the article is conveyed along a path through the inspection zone and the first and/or second beam axis is offset by between 30° and 60°, more preferably between 40° and 50°, and most preferably, is substantially equal to 45° from said path. Analogous orientations may be used to inspect a stationary article.

According to such embodiments, one or more image capture means may be positioned substantially above the article as it passes through the inspection zone. The arrangement of the lighting sources may be adapted where the image capture means is otherwise positioned.

Preferably, the lighting arrangement includes a plurality of said first light sources and/or a plurality of said second light sources and/or wherein said first light source is configured to produce a plurality of said first light beams and/or said second light source is configured to produce a plurality of said second light beams.

Known means may be used to produce a plurality of light beams from a single source.

Different light sources may be configured to illuminate the same, an overlapping or different portion of the article and/or different articles, In the case of there being more than article, a plurality thereof along the path of travel and/or substantially perpendicular thereto may be illuminated substantially simultaneously. In other words, more than one article may be illuminated (and inspected) at the same time, although they may be processed successively or in batches.

According to preferred embodiments, the or each first light source is closer to the article than the or each second light source. More particularly, the second light sources may be upstream or downstream of an article as it passes through an inspection zone, with the first light sources substantially at or adjacent the inspection zone. As will be apparent, particularly where an article is inspected as it moves, a each light source may operate as a said first or second light source at different points in time. According to one embodiment, a first light source is arranged to illuminate at least an upper portion of a first side of an article and a second light source is arranged to illuminate at least an upper portion of a second side of the article. Preferably, the first side of the article substantially opposes the second side.

The plurality of first and/or second light sources may be formed as an array having a plurality of rows and one or more columns.

As would be apparent to those skilled in the art, articles to be inspected will generally be conveyed along a path by some form of conveyor, such that they pass through a region in which the lighting arrangement of the invention is positioned to enable inspection to occur.

Preferably, the columns of the or each array are arranged to be substantially parallel to or along the path of the article during inspection, and the rows are arranged substantially perpendicular to the columns. A subset or the light sources preferably partially opposes another subset thereof so as to illuminate the article from different angles. As will be apparent to those in the art, articles may be conveyed along paths that are not straight and inspection of them may take place during such times. Consequently, the rows and / or columns may not be linear.

Additional light sources, similarly or otherwise arranged, may also be provided.

Preferably, at least one of the light sources includes an LED, more preferably, an LED tube.

Preferably, the first light source and/or the second light source is configured to emit infra-red light.

Preferably, the or each LED tube is mounted on a printed circuit board.

Preferably, the lighting arrangement includes or is coupleable to an external current controller for driving the first and second light sources.

According to a second aspect of the invention, there is provided an article inspection apparatus including: at least one lighting arrangement of the first aspect, the lighting arrangement being configured to illuminate at least a portion of an article; and an imaging system including first image capture means arranged to capture at least one image of at least a part of the portion of the article illuminated by the lighting arrangement.

The imaging system may include first and second image capture means arranged to capture an image of at least a part of the portion of the article illuminated by the lighting arrangement. The first and second image capture means may be configured to capture images of the same, different or overlapping portions of an article, or of different articles. Additional image capture means may be provided, as desired.

The lighting arrangement is preferably configured such that the desired illumination is achieved for the or each image capture means directed at the article in the inspection zone.

Multiple inspection zones may be provided for a single article with the same or different portions thereof illuminated and / or inspected in each zone.

Different light sources may be configured to cooperate with different image capture means.

Preferably, the article inspection apparatus includes conveyor means for conveying an article through the inspection zone, wherein the first (and for applicable embodiments, second and any additional) image capture means are configured to capture the images as the article is conveyed through the inspection zone. Again, it is noted that there may be more than one inspection zone, and / or different light sources and / or image capture means may be configured to operate within different portions of an inspection zone.

Any known conveyor means may be used and the invention is not limited to conventional belt- type arrangements, nor those on which articles are rotated as described in WO 03/23455. Furthermore, articles may be suspended from transport means or otherwise carried, rather than supported from underneath. Alternatively, as would be apparent to those skilled in the art, the article inspection apparatus, or at least components thereof, may additionally or alternatively be moveable, so as to enable the apparatus of the invention to inspect different articles or different portions of articles. The or each image capture means may be positioned as desired.

As would be apparent to those in the art, mirrors and / or other optical devices may be used to obtain a desired field of view.

Preferably, the imaging system is arranged to capture images for the entire article or substantially the entire article being inspected. To this end, the article may be rotated as it is conveyed through the inspection zone.

For the avoidance of doubt, it is to be noted that only one image capture means or camera is required. According to one embodiment, a single image capture means is mounted substantially directly above the article as it passes through the inspection zone although other arrangements may be used, depending in part on the conveyor means used and the form of the articles to be inspected

Preferably, the article inspection apparatus includes processing means for analysing images captured by the imaging system.

Preferably, the processing means is configured to analyse segments of the article captured at different stages of rotation of the article, the segments preferably having dimensions so as to substantially avoid any overlap therebetween.

Preferably, the processing means is configured to arrange said plurality of images to generate a substantially continuous picture of the surface of the article.

Preferably, the extent of overlap between adjacent images is the minimum to maintain said continuous picture of the surface of the article.

Preferably, the processing means is operable to identify a marking on the article from one or more of the images. Preferably, the processing means is operable to select an image of said marking for analysis purposes according to predetermined criteria.

The word "marking" is to be interpreted broadly as covering any form of defect which may be present on the surface of an article, including but not limited to discolouration, holes or punctures, or any other blemish.

Preferably, the conveyor means rotates the article at a speed so that it completes at least one complete revolution, but less than two complete revolutions while it is within the inspection zone.

According to one embodiment, the conveyor means includes two or more lanes for conveying articles past said imaging system. According to this embodiment, preferably, the lighting arrangement is configured to illuminate articles during their passage through an inspection zone in each lane. Additionally or alternatively, the article inspection apparatus may include a plurality of the lighting arrangements, each lighting arrangement for illuminating articles in one or more of the lanes of the conveyor means. Similarly, the image capture means may be configured to operate on a plurality of lanes, and/or the article inspection apparatus may include a plurality of imaging systems and / or image capture means arranged to process different lanes.

Where a light source is configured to illuminate articles in more than one lane, preferably, said light source is located at a sufficient or appropriate height to have a clear line of sight to articles in each said more than one lane. As will be apparent, where articles are suspended, the light source(s) and / or image capture mean(s) may be positioned below the article.

According to embodiments in which the lighting arrangement does not include the external current controller, preferably, this is included within the apparatus.

According to a third aspect, there is provided a system including two or more article inspection apparatus of the second aspect. According to a fourth aspect, there is provided a method of illuminating an article so as to at least reduce reflection spots in image(s) captured thereof, the method including: emitting a first light beam having a first predetermined angular beam width about a first central axis and configured such that it illuminates at least a portion of an article inside an inspection zone with the first beam axis offset from the article so that it does not impinge thereon at least when the article is inside the inspection zone, and/or emitting a second light beam having a second predetermined angular beam width about a second beam axis and arranged such that it illuminates at least a portion of the article inside the inspection zone with the second beam axis incident on the article but orientated such that the axis of light reflected off the article from the second light source is directed other than at the imaging system.

Preferably, the method includes illuminating at least a portion of the article with a plurality of said first and/or second light beams.

Preferably, the method includes capturing an image of at least a part of the portion of the article illuminated by the first light beam(s) and/or the second light beam(s).

One or more image capture means or cameras may be provided to achieve this end.

Preferably, the method includes analysing the captured images.

Further features of the method of the fourth aspect are analogous to features recited in relation to the first, second and third aspects.

Further aspects of the invention, which should be considered in all its novel aspects, will become apparent to those skilled in the art upon reading the following description which provides at least one example of a practical application of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will be described below by way of example only and without intending to be limiting with reference to the following drawings, in which: Figures 1 & 2 are end and plan views, respectively, of an apparatus of an embodiment of the invention.

Detailed Description of Preferred Embodiments

In broad terms, the invention provides means and methods for inspecting the surface(s) of an article inside an inspection zone wherein the light source(s) used to illuminate the article is configured to produce a light beam that is directed to be offset from the article such that the beam axis does not impinge on the article. The invention may have application to the detection of features on the surface of fruit, vegetables or other articles for grading purposes. In particular, the invention is envisaged to be suited to the analysis of the surface of articles that have a generally circular cross-section along at least one axis so that the article may be relatively easily rotated about that axis. Therefore, the invention may have particular application to articles such as oranges, apples, lemons and other articles having a similar shape. However, those skilled in the art may find applications of the present invention elsewhere.

More particularly, according to one embodiment, a lighting arrangement is provided for an inspection apparatus, where the inspection apparatus is for inspecting the surface of an article when the article is inside an inspection zone. The lighting arrangement includes a first light source for producing a first light beam having a first predetermined angular beam width about a first central axis, wherein the first light source is configured to illuminate at least a portion of the article inside the inspection zone such that the first central axis is offset from the article and does not impinge thereon at least when the article is inside the inspection zone.

Figures 1 and 2 show alternative views of an apparatus according to an embodiment of the invention. Included within Figures 1 and 2 are light sources 11, article to be inspected 12, conveyor 13, and processor 14 (omitted from Figure 2 for clarity). Also shown in Figure 1 are angular beam widths 15 and central beam axes 16. For clarity, the beam width is shown only for one beam in Figure 2. The arrows in Figure 2 show the direction of motion effected by conveyor 13. According to preferred embodiments, conveyor 13 additionally effects rotation to article 12, preferably about an axis substantially parallel to the surface of the conveyor, but substantially perpendicular to the direction of motion of the conveyor as marked by the arrows in Figure 2. Such conveyor arrangements are known to those skilled in the art. One such arrangement is described in the aforementioned WO 03/23455.

Figure 2 shows light source 11 producing multiple light beams but the invention is not limited thereto. Only one light beam is required according to the invention although a plurality of light beams are preferred. Furthermore, while light source 11 is shown producing a plurality of light beams, it will be appreciated that separate light sources may alternatively be used for each light beam. Furthermore, it is not essential for light beams to be configured to illuminate opposing sides of article 12 although this is preferred as it enables the whole of article 12 to be scanned more quickly.

As shown in Figures 1 and 2, light sources 11 are each configured to illuminate a portion of article 12 as it passes through an inspection zone. Light sources 11 are configured to emit a beam of light having a predetermined angular beam width 15. According to preferred embodiments, angular beam width 15 for each light source 11 is between 5° and 30°, but more preferably between 10° and 25° and most preferably between 15° and 20°. The preferred beam widths provide a greater light intensity over a smaller surface of article 12. Preferably, the beam width is substantially the same for each light source.

Particular embodiments of the invention are adapted to inspect articles having curved surfaces (for example, many types of fruit are substantially spherical or ovoid). As the radius of curvature of the articles being inspected increases, the amount of reflected light increases.

Thus, in practical implementations of the invention, angular beam width 15 and/or the orientation of beam axes 16 may be varied. More particularly, as the radius of curvature of the article increases, the more oblique the light beam is preferably configured relative to the object. Thus, the apparatus of the invention preferably provides for flexibility in the orientation of light source(s) 11 and/or angular beam width 15. The preferred angles and ranges described herein provide for a good level of performance in terms of reduced levels of reflection across a broad range of radii of curvature. However, the invention is not limited to these specific angles or ranges.

Image capture means (not shown) capture images of at least portions of article 12 as it passes through the inspection zone. The image capture means and light sources 11 are controlled by processor 14 such that the image capture means captures images of portions of article 12 as they are illuminated by light sources 11 so as to improve the quality of the images.

At least one image capture means, such as a camera, may be co-located or integral to each light source 11. However, the image capture means may be otherwise positioned within the scope of the invention, both as an alternative or in addition to any image capture means that may be provided at or adjacent light source 11. For example, one or more image capture means may be provided in the position of processor 14 in Figure 1.

The preferred arrangements of light sources 11 (including predetermined angular beam width 15 and orientation of light sources with respect to article 12) assist in preventing light being reflected off article 12 (particularly as white spots) and into the image capture means, thereby providing for improved quality in the images captured which in turn enables an improvement in the ability to identify blemishes etc in the surface of article 12. In some instances, reflection spots may not be eliminated but the occurrence and size thereof will generally be reduced.

Figure 2 includes reference line 19. According to preferred embodiments, the angle between reference line 19 and beam axes 16 (angle α in Figure 2, only shown once for clarity) is predetermined to prevent the beam axes 16 impinging on article 12 while it is inside the inspection zone and also to minimise the amount of reflected light. As described above, the size of article 12 will have an effect on this angle, as will beam width 15 and the distance between article 12 and light source 11. However, according to preferred embodiments, angle a is preferably between 30° and 60°, more preferably between 40° and 60°, and most preferably approximately equal to 45°.

Figure 1 includes reference line 18. According to preferred embodiments, the angle between reference line 18 and beam axes 16 (angle β in Figure 1, only shown once for clarity) is predetermined to minimise the amount of reflected light. As described above, this may be affected by the size of article 12, beam width 15 and the distance between article 12 and light source 11. However, according to preferred embodiments, angle β is preferably between 30° and 60°, more preferably between 40° and 50°, and most preferably approximately equal to 45°.

The orientations of the beam axes (and reference lines) may be manipulated depending on the conveyor system used. For example, if the articles are suspended while being conveyed, the light beams may be directed at an underside of the article so that images are captured which do not include any support means.

As will be apparent to those skilled in the art, the lighting arrangement of the present invention may be configured to form an array of light sources and/or a plurality of the light sources of the invention may be used in combination. According to such embodiments, a corresponding array of image capture means may be provided. Such arrays may be configured to illuminate articles 12 as they pass through an inspection site with additional upstream or downstream (relative to the conveyor) light sources each serve to illuminate the same article 12 but in different rotational orientations where such rotation is effected. Additionally or alternatively, arrays of light sources 11 may be used to illuminate articles 12 in batches, whereby each light source 11 illuminates multiple portions of a corresponding article 12. Furthermore, two or more processing lanes may be provided in parallel and the arrays may be configured to illuminate each said lane.

Suitable light sources will be apparent to those in the art. However, according to a presently preferred embodiment, one or more LED tubes are used. The LED tubes may be mounted on a printed circuit board (PCB). This configuration provides for an ease in manufacture and/or assembly, even when arrays of such light sources are required, since a plurality of the light sources may be mounted on the same PCB and/or multiple PCBs may be located adjacent to one another or otherwise positioned, as required.

The inventors have noticed that the light intensity emitted by an LED tube quickly drops as temperature increases. Thus, according to preferred embodiments of the invention, the current source and/or controller used to drive the light sources is situated external thereto (i.e., located remote therefrom) such that heat dissipated thereby does not affect the LED tubes. The particular light sources used may be selected as required depending on the object to be illuminated and the types of defects or blemishes to be detected. Furthermore, each article may be separately illuminated by different types of light sources and/or viewed by different types of camera so as to optimise detection by the system of more than one type of defect or blemish.

According to one embodiment, infra-red (IR) light sources (e.g. LED tubes) are used to illuminate articles with images being captured by IR cameras. Such an arrangement is well suited to inspecting, for example, the surfaces of fruit because punctures and bad/decayed portions of fruit are readily identifiable as dark portions in the captured images.

Alternatively, ultra-violet light or light having a different wavelength may be used depending on what the system is trying to detect.

Where in the foregoing description reference has been made to specific components or integers of the invention having known equivalents, then such equivalents are herein incorporated as individually set forth.

It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be included within the present invention.

Claims

1. A lighting arrangement for an inspection apparatus, the inspection apparatus including an imaging system for capturing at least one image of the surface of an article when the article is inside an inspection zone, the lighting arrangement including: one or more light sources configured to illuminate said article so as to at least reduce reflection spots in the captured image(s), wherein a first said light source is configured to produce a first light beam having a first predetermined angular beam width about a first beam axis and arranged such that it illuminates at least a portion of the article inside the inspection zone with the first beam axis offset from the article so it does not impinge thereon at least when the article is inside the inspection zone, and/or wherein a second said light source is configured to produce a second light beam having a second predetermined angular beam width about a second beam axis and arranged such that it illuminates at least a portion of the article inside the inspection zone with the second beam axis incident on the article but orientated such that the axis of light reflected off the article from the second light source is directed other than at the imaging system.

2. The lighting arrangement of claim 1 , wherein the first and/or second beam width is between 15° and 20°.

3. The lighting arrangement of claim 1 or claim 2, wherein the first and/or second beam axis is offset by substantially 45° from vertical.

4. The lighting arrangement of any one of the preceding claims, wherein the article is conveyed along a path through the inspection zone and the first and/or second beam axis is offset by substantially 45° from said path.

5. The lighting arrangement of any one of the preceding claims, including a plurality of said first light sources and/or a plurality of said second light sources and/or wherein said first light source is configured to produce a plurality of said first light beams and/or said second light source is configured to produce a plurality of said second light beams.

6. The lighting arrangement of any one of the preceding claims, wherein at least one said light source includes an LED tube.

7. The lighting arrangement of claim 6, wherein the or each LED tube is mounted on a printed circuit board.

8. The lighting arrangement of claim 6 or claim 7, including or configured to couple to an external current controller.

9. An article inspection apparatus including: at least one lighting arrangement according to any one of the preceding claims; and an imaging system including at least one image capture means for capturing an image of at least a portion of the article illuminated by the lighting arrangement.

10. The article inspection apparatus of claim 9, wherein the imaging system includes first and second image capture means each configured to capture an image of a different portion of the article.

11. The article inspection apparatus of claim 10, wherein the different ' portions partially overlap.

12. The article inspection apparatus of any one of claims 9 to 12, including means for conveying the article through the inspection zone.

13. A method of illuminating an article so as to at least reduce reflection spots in image(s) captured thereof, the method including: emitting a first light beam having a first predetermined angular beam width about a first beam axis and arranged such that it illuminates at least a portion of the article inside an inspection zone with the first beam axis offset from the article so it does not impinge thereon at least when the article is inside the inspection zone, and/or emitting a second light beam having a second predetermined angular beam width about a second beam axis and arranged such that it illuminates at least a portion of the article inside the inspection zone with the second beam axis incident on the article but orientated such that s the axis of light reflected off the article from the second light source is directed other than at the imaging system.

14. A lighting arrangement substantially as herein before described with reference to Figures 1 and 2 of the drawings.

15. An article inspection apparatus substantially as herein before described with reference to Figures 1 and 2 of the drawings.

16. A method substantially as herein before described with reference to Figures 1 and 2 of the drawings.