Image-based inspection device

Abstract

Imaged Based Inspection Device An image-based inspection device (2) comprises a transparent portion (4) for receiving grains to be inspected, as received grains; an imaging system (6) configured to capture a plurality of spatially co- registered images of the received grains, as captured images, each of which is an image of the received grains illuminated at a different illumination angle; an image processor (8) connected to the imaging system (6) for processing the captured images by combining them to form a composite image in which artifacts caused by the illumination at the different illumination angles are minimised; and an inspection unit (10) operable to receive the composite image and to apply one or more image evaluation algorithms to determine thereby visual characteristics of individual grains of the received grains in the composite image.

Description

Imaged-Based Inspection DeviceFIELD OF INVENTION

[0001] The present invention relates to an image-based inspection device for a particulate material, particularly to an imaged-based inspection device for inspecting individual seeds, pulses, grains, kernels or similar from horticultural and agricultural origins, mineral or metallic grains, or granulated, powdered or pelletized substances or other particulates (herein collectively referred to as 'grains').BACKGROU ND OF THE INVENTION

[0002] Grains inspection for sorting, grading and related applications for quality control, process control, food safety are today mostly carried out in automated processes. Automation streamlines the inspection process by eliminating the inconsistencies associated with manual visual assessment, all while optimizing time and cost savings compared to human labour. Such an inspection process is typically based on a grains sample from a grains consignment being illuminated, whereupon a two-dimensional (2D) image in which individual grains comprising the grains sample are discernable is generated for analysis to determine one or more visually manifest characteristics of the individual grains and / or the grains sample useable by the device to sort, grade or perform related applications.

[0003] A known image based-inspection device for the inspection of grains of a horticultural or an agricultural origin is disclosed in JP6292852B and includes an upper imaging / illumination unit, a lower illumination unit, and a tray having a transparent portion disposed between the upper imaging / illumination unit and the lower illumination unit, on which portion an arbitrary number of grains to be discriminated are dispersed so as to minimise overlap between individual grains. Light is emitted from the upper light emitting unit of the upper imaging / illumination unit to the dispersed grains, and the scattered light is imaged by the upper imaging / illumination unit to generate scattered image data, or light is emitted from the lower light emitting unit of the lower illumination unit to the grains and transmitted light is imaged by the upper imaging unit to generate transmitted image data. A computer is provided which obtains the transmitted and / or scattered image data of the grains obtained from the imaging and compares the obtained image data with image data related to standard images of reference grains.

[0004] To improve the accuracy of the inspection device it is desirable to obtain images from both above and below a grains sample. Typically, in such configurations the grains sample is dispersed on a transparent support surface, and there are cameras above and below it. Such a configuration is disclosed, for example, in WO2022137817A and comprises an image-based inspection device having a tray with atransparent portion on which grains to be inspected are to be dispersed; an upper camera that is disposed above the transparent portion and is capable of imaging the upper surface of grains dispersed thereon; a lower camera that is disposed below the transparent portion and is capable of imaging the lower surface of the grains dispersed thereon; an upper light source that is disposed above the transparent portion and is capable of illuminating the upper surface of the grains; a first lower light source that is disposed below the transparent portion and is capable of illuminating the lower surface of the grains; and a computer configured to identify the same grains in the upper and lower images and to determine therefrom one or more characteristics of the individual grains and / or the grains sample.

[0005] As will be appreciated, for technical imaging of many things, the standard choice is to use diffuse illumination. Diffuse Illumination means that there is no single strong light source, but that the light comes to the sample equally from all directions. This method of illumination ensures that specular reflections and strong highlights on the sample are minimised, and therefore the color of the sample is recorded more accurately.

[0006] It will be further appreciated that the background behind the grains sample as seen by each camera should be the same and preferably selected to enhance the contrast between it and the grains being imaged, for example a black background. Unfortunately, the provision of such backgrounds means that a light diffuser cannot be placed above or below the transparent portion of the support surface on which the grains sample rests when two cameras are employed. This forces the use of directional lights, which then causes highlights on the individual grains of the grains sample.

[0007] However, even with these devices which employ two cameras and a same, uniform background it is desirable to obtain images that look like they were acquired with diffuse illumination.SU M MARY OF TH E INVENTION

[0008] In a first aspect the present invention relates to an image-based inspection device comprising a transparent portion having an upper surface for receiving grains to be inspected, as received grains, and a lower surface opposing the upper surface; an imaging system configured to capture a plurality of spatially co-registered images of the received grains, as captured images, each image of the captured images being an image of the received grains illuminated at a different illumination angle in a plane parallel to the upper surface of the transparent portion; an image processor connected to the imaging system to receive the captured images and configured to process the received captured images to generate a processed image; and an inspection unit configured to receive the processed image and to apply one or more image evaluation algorithms to it to determine thereby visual characteristics of individual grains of the received grains; wherein the image processor is adapted to process the receivedcaptured images by combining them to form a composite image as the processed image, in which processed image artifacts caused by the illumination at different illumination angles are reduced.

[0009] When the plurality of spatially co-registered images which are acquired by the imaging system are combined into the single composite image as the processed image then image artefacts caused by illumination at different illumination angles are reduced in that processed image. For example, by combining the captured images by taking a median value of the same pixel or group of pixels in each of the spatially co-registered captured images the composite image appears as if it were obtained using a source of diffuse illumination and shadows and highlights in the imaged received grains are minimized.

[0010] In some embodiments the imaging system comprises one or both an upper imaging module and a lower imaging module, each imaging module being configured to acquire images of the received grains, with the upper imaging module including an upper illumination module disposed on the same side of the transparent portion as the upper surface and configured to illuminate the upper surface when energised and an upper imaging unit disposed on a same side of the transparent portion as the upper surface having a field of view comprising at least a portion of the upper surface and adapted to capture images of an upper surface of the received grains as upper images, and with the lower imaging module including a lower illumination module disposed on the same side of the transparent portion as the lower surface and configured to illuminate the lower surface when energised and a lower imaging unit disposed on the same side of the transparent portion as the lower surface having a field of view comprising at least a portion of the lower surface and adapted to capture images of a lower surface of the received grains as lower images, the captured images received by the image processor being one or both the upper images and the lower images.

[0011] Thus, images of both upper and lower surfaces of individual grains of the received grains by be readily imaged. To assist with the spatial correlation between the same grains imaged in the upper and the lower images it is useful if each of the upper and the lower imaging units are arranged so that their optical axis are co-axial.

[0012] In some embodiments each of the upper illumination module and the lower illumination module comprises a plurality of separately energisable upper illuminators and lower illuminators respectively, each illuminator of which is configured to, when energised, illuminate the received grains at a different illumination angle from the illumination provided by the other illuminators of the plurality of separately energisable illuminators; the upper imaging unit is operable in synchronism with the energization of each of the upper illuminators separately to generate the upper images comprising at least one image captured from illumination provided by each separately energised upper illuminator; and the lowerimaging unit is operable in synchronism with the energization of each of the lower illuminators separately to generate the lower images comprising at least one image captured from illumination provided by each separately energised lower illuminator.

[0013] Usefully, the image-based inspection device according to the present invention is adapted to illuminate each of the upper and / or lower surfaces at at least three different illumination angles. This avoids the situation which may arise when illuminating at only two different illumination angles where a pixel may be highlighted in one image, taken under illumination at one illumination angle, but in shadow in the other image, taken under illumination at the other illumination angle. Thus, this may result in the composite image containing no meaningful image information about the point on the imaged grain represented by that pixel.

[0014] Most usefully, the angular separation between the different illumination angles should be maximized, so that their angular separation about a circle in the plane parallel to the upper surface is evenly spaced (for example, with illumination at three different illumination angles the three illuminators providing the illumination should preferably by spaced with 120° relative angular separation; at four different illumination angles then the four illuminators providing the illumination are preferably spaced apart about the circle by 90°; five illumination angles using five illuminators relatively spaced apart by 72° and so on). Maximizing the angular separation between each of the plurality of different illumination angles ensures that highlights and shadows on grains imaged in the plurality of spatially co-registered images are separated as much as possible.

[0015] In a second aspect the present invention relates to a method for image-based grains inspection comprising the steps of:(a) feeding grains to be inspected into a transparent portion of an image-based inspection device according to the first aspect of the present invention;(b) obtaining by means of the image-based inspection device a plurality of spatially co-registered images of the received grains, as captured images, each image of the captured images being an image of the received grains illuminated at a different illumination angle;(c) processing by means of the image-based inspection device the captured images to form a composite image, in which composite image artifacts caused by the illumination at different illumination angles are minimised; and(d) applying by means of the image-based inspection system one of more image data evaluation algorithms to the composite image to determine thereby visual characteristics of individual grains of the received grains.BRIE F DESCRI PTION OF DRAWI NGS

[0016] Exemplary embodiments of the invention are described below with reference to the figures of the accompanying drawings, of which:FIG. 1 shows a simplified schematic of an instrument incorporating an embodiment of an inspection device according to the present invention;FIG. 2 shows a simplified depiction of an imaging module useable in the inspection device according to the present invention, including that illustrated in the embodiment of FIG. 1;FIGS. 3 show upper images (a)-(d) of cereal kernels as received grains each taken at a different illumination angle;FIGS.4 (a)-(d) show the same images as FIGS.3 (a)-(d) after pre-processing to standardize intensity;FIG. 5 shows a composite image obtained by combining images FIGS.4 (a)-(d);FIGS. 6 show lower images (a)-(d) of spheres as received grains each taken at a different illumination angle;FIGS.7 (a)-(d) show the same images as FIGS.6 (a)-(d) after pre-processing to standardize intensity; andFIG. 8 shows a composite image obtained by combining images FIGS.7 (a)-(d).DETAILED DESCRIPTION OF TH E I NVENTION

[0017] A detailed description of the invention follows which is made with reference to the exemplary embodiments depicted in figures described above.

[0018] An exemplary embodiment of an image-based inspection device according to the first aspect of the present invention is illustrated in a simplistic form in FIG. 1 and shows the operable configuration of the major components of the present device. The image-based inspection device 2 is illustrated as comprising a transparent portion 4, here realized as a glass plate, having an upper surface 4U for receiving grains to be inspected, as received grains, and a lower surface 4L opposing the upper surface 4U; an imaging system 6 adapted to capture spatially co-registered images of the received grains, as captured images, each image of which being an image of the received grains illuminated at a different illumination angle in a plane parallel to the upper surface 4U of the transparent portion 4 and each being spatially co-registered with the others so that a same pixel or a location in each captured image represents a same location in the scene being imaged (which here comprises the received grains); an image processor 8 operably connected to the imaging system 6 to receive the captured images in digitalformat and configured to process the received captured images to generate a processed image therefrom; and an inspection unit 10 operable to receive the processed image in digital format and to apply one or more image evaluation algorithms to each of them to determine visual characteristics of individual grains of the received grains.

[0019] The embodiment of the image-based inspection system 2 that is illustrated in FIG. 1 further comprises a hopper 14; a feeder 16; a bin 18; vibrators 20; a high-walled (high relative to the size of the individual grains of the received grains) frame 22; a display / user interface 24; and a housing 26. The hopper 14 is provided as a store for a sample of grains to be inspected and has an upper opening 28 connected to an opening 30 in the housing 26 through which the sample of grains can be supplied to the device 2. The hopper 14 has a lower opening 32 through which grains of the stored grains sample can be provided into the feeder 16 via an upper opening 34. A divider 36 is provided as an element of the feeder 16 to receive grains provided through the upper opening 34 and operates to divide the stored grain sample into lots which are then deposited on to the upper surface 4U, as received grains, via a lower opening 38 of the feeder 16. The high-walled frame 22 is located with a lower surface 40 on or proximal the upper surface 4U of the transparent portion 4 such that its walls act to retain the received grains on at least a portion of the upper surface 4U for imaging by the imaging system 6 and any space between its lower surface 40 and the upper surface 4U is not more than a minimum expected height of individual grains pf the received grains.

[0020] In the present embodiment, the vibrators 20 operate to vibrate the transparent portion 4 in a linear fashion to distribute the received grains over the upper surface 4U within the constraints of the highwalled frame 22 to minimize, preferably eliminate, overlap of the grains in images captured by the imaging system 6 once the vibrators 20 cease to operate. The received grains are collected in the bin 18 after the capture of a predetermined number of images. To do this, in the present invention the frame 22 is made moveable in a plane parallel with the upper surface 4U to sweep the received grains from the upper surface 4U and into the bin 18.

[0021] The imaging system 6 according to present invention may comprise one or both an upper imaging module 42U which is configured to capture spatially co-registered images of an upper surface of the received grains, as upper images, and a lower imaging module 42L which is configured to capture spatially co-registered images of a lower surface of the received grains, as lower images. The imagebased inspection device 2 of the present embodiment is shown as comprising both upper 42U and lower 44L imaging modules. The upper imaging module 42U here includes an upper illumination module 44U disposed on the same side as the upper surface 4U and is composed of a plurality of separatelyenergisable upper illuminators 48U for illuminating the upper surface 4U when energised and an upper imaging unit 46U disposed on a same side as the upper surface 4U configured to capture the upper images having a field of view (illustrated by dashed line 50U) comprising at least a portion of the upper surface. The upper illuminators 48U and the upper imaging unit 46U are adapted to operate in synchronism such that during the energization of each upper illuminator 48U the upper imaging unit 46U is operated to capture an image of received grains under illumination from that energised upper illuminator 48U i.e., the upper imaging unit 46U initiates capture of an image upon or after the commencement of the energization of that upper illuminator 48U and stops the capture of the image before or upon cessation of the energization of that same upper illuminator 48U. Thus, after energizing each of the upper illuminators 48U in turn the upper imaging unit 46U has captured a plurality of spatially co-registered upper images comprising images obtained under illumination by each of the upper illuminators 48U. It is envisaged that the upper imaging unit 46U may be a digital camera, having a rectangular sensor with megapixel (preferably not less than 5 megapixels, more preferably not less than 10 megapixels, typically not less than 12 megapixels) resolution and with a Bayer filter (for RGB imaging). The lower imaging module 42L here includes a lower illumination module 44L disposed on the same side as the lower surface 4L and is composed of a plurality of separately energisable lower illuminators 48L for illuminating the lower surface 4L when energised and a lower imaging unit 46L, similar in construction to the upper imaging unit 46U, disposed on a same side as the lower surface 4L configured to capture the lower images and having a field of view (illustrated by dashed line 50L) comprising at least a portion of the lower surface 4L. The lower imaging module 42L being configured to operate in a manner analogous to the upper imaging module 42U to capture a plurality of spatially coregistered lower images comprising images obtained using illumination from each of the lower illuminators 48L separately. Usefully the optical axis CU of the upper imaging unit 46U and the optical axis CL of the lower imaging unit 46L are aligned to allow upper and lower images of the received grains to accurately correspond.

[0022] To facilitate grain segmentation in images generated by the image-based inspection device and to minimize the effects in the generated images of the interaction of stray light with the received grains a background, preferably a uniform background, is usefully provided as an element of the device against which images are captured. The colour of such a background may be selected to enhance contrast between it and the received grains in any captured image and may be black. In the exemplary embodiment of the image-based inspection device 2 of FIG. 1 where the imaging system 6 comprises an upper imaging module 42U and a lower imaging module 42L located on opposite sides of thetransparent portion 4 then the background can be provided as an upper background 52U and a lower background 52L, which here, conveniently, respectively form parts of the upper imaging module 42U and the lower imaging module 42L. The upper background 52U acts as a background against which the lower imaging unit 46L will capture images of received grains and therefore is formed to extend over the field of view 50L of the lower imaging unit 46L and is located outside of the field of view 50U of the upper imaging unit 46U. Similarly, the lower background 52L acts as a background against which the upper imaging unit 46U will capture images of received grains and therefore is formed to extend over the field of view 50U of the upper imaging unit 46U and is located outside of the field of view 50L of the lower imaging unit 46L.

[0023] Referring now to FIG. 2, an embodiment of an imaging module, such as the upper imaging module 42U and / or the lower imaging module 42L of FIG. 1, according to the present invention is illustrated in a simplistic form. For ease of understanding, reference will be made only to the upper imaging module 42U but it is to be understood that the lower imaging module 42L may be identically constructed and that by describing this aspect of the present invention with reference to the upper imaging module 42U it is not to be implied that an embodiment which utilizes only a bottom imaging module 42L falls outside of the scope of the present invention.

[0024] The upper imaging module 42U includes an upper imaging unit 46U and an upper illumination module 44U. The upper illumination module 44U comprises a plurality (here four) of separately energisable upper illuminators 48Ua, 48Ub, 48Uc 48Ud. Each upper illuminator (44Ua say) is configured to, when energised, provide illumination over substantially all the upper surface 4U to illuminate the upper surface 4U at a different illumination angle in a plane parallel to the upper surface 4U from the illumination provided by the other upper illuminators (48Ub, 48Uc 48Ud say) of the plurality of upper illuminators 48Ua, 48Ub, 48Uc 48Ud. It is useful to place the plurality of upper illuminators 48Ua, 48Ub, 48Uc 48Ud in a geometric pattern that reflects the geometric field of view 50U of the upper imaging unit 46U, which here is rectangular, to enhance the homogeneity of illumination.

[0025] Generally, it is preferred that an illumination module according to the present invention comprises illuminators arranged to illuminate the upper surface 4U at three or more different illumination angles and this illumination module therefore comprises the equivalent three or more illuminators. Employing at least three illuminators avoids the situation which may arise when illuminating at only two different illumination angles, where a pixel may be highlighted in one image, taken under illumination at one illumination angle, but in shadow in the other image, taken under illumination at the other illuminationangle. Thus, this may result in the composite image containing no meaningful image information about the point on the imaged grain represented by that pixel.

[0026] Most usefully, the angular separation between the directions of illumination in a plane parallel to the upper surface 4U of adjacent illuminators should be maximized, so that their angular separation about a circle in the plane parallel to the upper surface 4U is evenly spaced. For example, with illumination at three different illumination angles the three illuminators providing the illumination should preferably by spaced with 120° relative angular separation; at four different illumination angles then the four illuminators providing the illumination are preferably spaced apart about the circle by 90°; five illumination angles using five illuminators relatively spaced apart by 72° and so on. Maximizing the angular separation between the directions of illumination in a plane parallel to the upper surface 4U of adjacent illuminators helps ensure that highlights and shadows on grains imaged in the plurality of spatially co-registered images are separated as much as possible. It will be appreciated that the more illuminators which are employed in the invention the closer the composite image will be to an image acquired with diffuse illumination.

[0027] Returning to the upper imaging module 42U depicted in FIG. 2, each of the plurality of upper illuminators 48Ua, 48Ub, 48Uc 48Ud of the present embodiment is a strip illuminator for providing illumination from one of the four edges of the rectangular field of view 50U and over the upper surface 4U. Each strip illuminator may be realized as a linear array of Light Emitting Diodes (LEDs) 54a..d located in a rectangular housing 56 along its short 56S and long 56L sides and directed inwardly. Usefully, and as illustrated in FIG. 2 each linear array of LEDs 54a..d is a two-dimensional array comprising two rows of LEDs, an outside row 58a..d and an inside row 60a..d with the LEDs of the outside row 58a..d being angled to illuminate the nearest end and the LEDs of the outside row 60a..d being angled to illuminate the farthest end. Due to the rectangular layout of the imaging area the outside row 58a..d of LEDs are angled differently to the inside row 60a..d of LEDs to provide a more homogeneous illumination of the upper surface 4U. It is preferred that at least some of the LEDs are white light LEDs to provide captured images that better match the human visual perception.

[0028] The upper imaging unit 46U is collocated with the rectangular housing 56 and arranged with its optical axis CU passing through the centre of the rectangle. In the present embodiment the rectangular housing 56 is formed with a solid base plate 62, around the periphery of which the linear arrays of LEDs 54a..d of the upper illuminators 48Ua..d are arranged and is provided with a central opening 64 through which the externally mounted upper imaging unit 46U images the upper surface 4U. The upper background 52U covers this base, except in the region of the central opening 64. In some embodiments the centralopening 64, and in some embodiments also the upper background 52U, may be covered with a transparent protector 66 which acts as protection against dust and dirt.

[0029] Usefully the optical axis CU of the upper imaging unit 46U is aligned with the optical axis CL of the lower imaging unit 46L, when present, to allow the top and bottom views of the grains to correspond accurately in the images obtained by the upper imaging unit 46U (upper images) and the lower imaging unit 46L (lower images).

[0030] In the present embodiment, and as illustrated in FIG. 1, the image processor 8 and the inspection unit 10 are functionally realized as elements of a suitably programmed microprocessor device 12. The microprocessor device 12 is configured to store and execute assorted programs and routines which, when executed, cause the selective operations of the various components of the device 2 as earlier described and which cause the functional realization of both the image processor 8 and the inspection unit 10. It will be appreciated that in other embodiments some or all of the functional components of the microprocessor device 12 may be realized by separate physical components or may be located external of the housing 26 and physically or wirelessly connected to cause the selective operations of the various components of the device 2 as earlier described and also cause the functional realization of one or both the image processor 8 and the inspection unit 10.

[0031] According to the present invention, the microprocessor device 12 may be programmed to realize the inspection unit 10 that is adapted to determine visual characteristics using Deep Learning (DL) algorithms. These DL algorithms are used for segmentation and characterization of the received grains in the processed images and are provided in the form of a combination of algorithms in conjunction with training data comprising images, as is known in the art.

[0032] The microprocessor device 12 may also or alternatively be programmed to realize the image processor 8. However realized, the image processor 8 is adapted to receive the plurality of spatially co-registered captured images (upper images say) obtained using the upper imaging unit 46U, say, with illumination from different illumination angles and to combine these spatially co-registered captured images, with or without image pre-processing, into a single composite image in which image artefacts caused by illumination at different illumination angles by each of the illuminators (upper illuminators 48U say) are reduced and to make that composite image available to the inspection unit 10 as the processed image. The so realized image processor 8 is adapted, in an identical manner, to receive and to process a plurality of spatially co-registered captured images (lower images) obtained using the lower imaging unit 46L, when present.

[0033] The image processor 8 of the present embodiment is adapted to operate to combine the spatially coregistered captured images by forming a median value of a same pixel or group of pixels in each of the captured images to form the composite image. Alternatively, a non-homogeneously weighted average may be employed to form the composite image to take particular artefacts into account.

[0034] In some embodiments the image processor 8 operates to pre-processes each of the spatially coregistered captured images to equalize the brightness of the illumination across each image. This may be done by acquiring images of a white standardization target where each image is captured using illumination from a separate one of the illuminators and evaluating the light distribution of each illuminator. The so evaluated light distribution is then employed to equalize the brightness in the captured images. It is envisaged that in other embodiments some operations performed in the present embodiment by the image processor 8 may be performed by the inspection unit 10 and vice versa.

[0035] Additionally, the microprocessor device 12 may be configured to generate control signals for use by controllers to control, in a known fashion, the operation of other elements of the image-based inspection device 2. For example, it is envisaged that the microprocessor device 12 provides a control signal to the divider 36 to cause it to operate to receive a lot of grains held in the hopper 14 and deliver the lot onto the upper surface 4U of the transparent portion 4 as received grains; to provide a control signal to the vibrator 20 to cause it to operate and provide vibrational energy to the transparent portion 4 and the received grains to distribute the received grains over the upper surface 4U within the constraints of the high-walled frame 22 and minimize, preferably eliminate, overlap of the individual grains comprising the received grains; to provide control signals to the imaging system 6 to cause the synchronous operation of the illuminators 48U,48L and the imaging units 46U,46L as described above; and then to provide a control signal to the high-walled frame 22 to cause it to move in a plane parallel with the upper surface 4U and sweep the received grains from the upper surface 4U into the bin 18.

[0036] In FIGS. 3 -5 there are shown images of cereal kernels as received grains obtained using an upper imaging module 42U. FIGS. 3 shows a plurality of unprocessed images captured by the upper imaging unit 46U of the upper imaging module 42U. Each image of the images (a) to (d) is captured by the upper imaging unit 46U with the received grains being illuminated at a different illumination angle in a plane parallel with the upper surface 4U, by the selective energization of a different one of the linear array of LEDs 54 (a) to (d), corresponding to a different one of the upper illuminators 48U (a) to (d), to provide a plurality (here four) spatially co-registered images as captured images. FIGS. 4 (a) to (d) shows the same images as those of FIGS 3 (a) to (d) after processing by the image processor 8 to equalize the brightness for all of the captured images in FIGS. 3 (a) to (d). FIG. 5 shows a single composite image in which imageartefacts caused by illumination at different illumination angles by each of the illuminators (upper illuminators 48U say) have been reduced by forming a median value of a same pixel or group of pixels in each of the processed captured images of FIGS. 4 (a) to (d). Amongst other things, bright highlights in the images of FIGS. 3 (a) to (d) and FIGS.4 (a) to (d) have been reduced in the image of FIG.5, making it more like images which would have been obtained had a source of diffuse illumination been used to capture a single image.

[0037] In FIGS. 6-8 there are shown images of spherical objects as received grains obtained using a lower imaging module 42L. FIGS. 6 shows a plurality of unprocessed images captured by the lower imaging unit 46Lof the lower imaging module 42L. Each image of the images (a) to (d) is captured by the lower imaging unit 46L with the received grains being illuminated at a different illumination angle in a plane parallel with the upper surface 4U, by the selective energization of a different one of the lower illuminators 48L (a) to (d) say to provide a plurality (here four) spatially co-registered images as captured images. FIGS. 7 (a) to (d) shows the same images illustrated FIGS 6 (a) to (d) after processing by the image processor 8 to equalize the brightness in the captured images shown in FIGS 6 (a) to (d). FIG. 8 shows a single composite image in which image artefacts caused by illumination at different illumination angles by each of the illuminators (lower illuminators 48L say) have been reduced by forming a median value of a same pixel or group of pixels in each of the processed captured images of FIGS. 7 (a) to (d). Amongst other things, the prominence of scratches on the transparent portion 4 which were visible in the images of FIGS. 6 and FIGS. 7 is reduced in the composite image of FIG. 8.

[0038] It is envisaged that in some embodiments the transparent portion 4 may form some or all of a bottom surface of a removable tray which is locatable in and removable from the housing 26. It is envisaged that in these embodiments the tray is removed to allow manual placement of grains on, and their removal from, the transparent portion 4.

[0039] It is also envisaged that in some embodiments the transparent portion 4 may have grooves or indentations formed in its upper surface 4U to facilitate the non-overlapping arrangement and the alignment of the individual grains of the received grains.

[0040] It is further envisaged that in some embodiments the imaging system 6 may operate to collect a plurality of spatially co-registered images at each of the different illumination angles and the plurality combined to form the composite image.

[0041] It will be appreciated that the grains are not limited to grain and seed of agricultural or horticultural origin but are to be considered as herein defined.

Claims

1. An image-based inspection device (2) comprisinga transparent portion (4) having an upper surface (4U) for receiving grains to be inspected, as received grains, and a lower surface (4L) opposing the upper surface (4U);an imaging system (6) configured to capture a plurality of spatially co-registered images of the received grains, as captured images, each image of the captured images being an image of the received grains illuminated at a different illumination angle in a plane parallel to the upper surface (4U) of the transparent portion (4);an image processor (8) connected to the imaging system (6) to receive the captured images and configured to process the received captured images to generate a processed image; andan inspection unit (10) configured to receive the processed image and to apply one or more image evaluation algorithms to it to determine thereby visual characteristics of individual grains of the received grains; whereinthe image processor (8) is adapted to process the received captured images by combining them to form a composite image as the processed image, in which processed image artifacts caused by the illumination at the different illumination angles are reduced.

2. The image-based inspection device (2) as claimed in Claim 1, whereinthe imaging system (6) is configured to capture images at the plurality of different illumination angles which illumination angles are evenly spaced apart about a circle in the plane parallel to the upper surface (4U).

3. The image-based inspection device (2) as claimed in Claim 1, whereinthe imaging system (6) comprises one or both an upper imaging module (42U) and a lower imaging module (42L), each imaging module (42U;42L) being configured to acquire images of the received grains, with the upper imaging module (42U) including an upper illumination module (44U) disposed on the same side of the transparent portion (4) as the upper surface (4U) and configured to illuminate the upper surface (4U) when energised and an upper imaging unit (46U) disposed on a same side of the transparent portion (4) as the upper surface (4U) having a field of view (50U) comprising at least a portion of the upper surface (4U) and adapted to capture images of an upper surface of the received grains as upper images, and with the lower imaging module (42L) including a lower illumination module (44L) disposed on thesame side of the transparent portion (4) as the lower surface (4L) and configured to illuminate the lower surface (4L) when energised and a lower imaging unit (46L) disposed on the same side of the transparent portion (4) as the lower surface (4L) having a field of view (50L) comprising at least a portion of the lower surface (4L) and adapted to capture images of a lower surface of the received grains as lower images, the captured images received by the image processor (8) being one or both the upper images and the lower images.

4. The image based inspection device (2) as claimed in Claim 3, whereineach of the upper illumination module (44U) and the lower illumination module (44L) comprises a plurality of separately energisable upper illuminators (48Ua..d) and lower illuminators (48La..d) respectively, each illuminator (48Ua; 48La) of which is configured to, when energised, illuminate the received grains at a different illumination angle from the illumination provided by the other illuminators (48Ub..d; 48Lb..d) of the plurality of separately energisable illuminators (48Ua..d;48La..d); whereinthe upper imaging unit (46U) is operable in synchronism with the energization of each of the upper illuminators (48Ua..d) separately to generate the upper images comprising at least one image captured from illumination provided by each separately energised upper illuminator (48U a,b,c or d); and whereinthe lower imaging unit (46L) is operable in synchronism with the energization of each of the lower illuminators (48La..d) separately to generate the lower images comprising at least one image captured from illumination provided by each separately energised lower illuminator (48La,b,c or d).

5. The image-based inspection device (2) as claimed in Claim 4, whereinthe upper illuminators (48Ua..d) are disposed outside the field of view (50L) of the lower imaging unit (46L) and the lower illuminators (48La..d) are disposed outside the field of view(50U) of the upper imaging unit (46U).

6. The image-based inspection device (2) as claimed in Claim 1, whereinthe image processor (8) is adapted to form the composite image by combining the received captured images into a median image generated by calculating a median intensity value of pixels at a same location in each of the received captured images.

7. The image-based inspection device (2) as claimed in Claim 3, whereinthe image processor (8) is adapted to form a first composite images as a median image by calculating a median intensity value of pixels at a same location in each image of the upper15images and to form a second composite image as a median image by calculating a median intensity value of pixels at a same location in each image of the lower images.

8. The image-based inspection device (2) as claimed in Claim 4, whereineach illuminator of the plurality of illuminators (48Ua..d) comprises a linear array of LEDs (54a..d) arranged so that the linear arrays of LEDs (54a..d) of all of the plurality of illuminators (48Ua..d) are disposed to together form a same geometric shape as the geometric shape of the field of view (50U).

9. The image-based inspection device (2) as claimed in Claim 8, whereinthe transparent portion (4) has a rectangular geometric shape and the linear arrays of LEDs (54a..d) of the plurality of illuminators (48Ua..d) are disposed at substantially 90 degrees to one another in a plane parallel to a plane containing the transparent portion (4).

10. The image-based inspection device (2) as claimed in Claim 8 or Claim 9, whereinthe linear array of LEDs(54a..d) in each of the plurality of illuminators (48Ua..d) comprises two rows of LEDs (58a..d; 60a..d) with the LEDs of one row (58a..d) mounted to provide illumination at a different illumination angle in a plane perpendicular to the plane containing the transparent portion (4) to the illumination provided by the LEDs in the other row (60a..d).

11. The image-based inspection device (2) as claimed in Claim 4, whereinthe image processor (8) is adapted to process each of the received captured images to compensate for distance dependent variations in illumination intensity over the transparent portion (4) of the illuminator energised for the generation of that received captured image.

12. The image-based inspection device (2) as claimed in Claim 11, whereinan image of a standardization target obtained under illumination of a single illuminator (48Ua) of the plurality of illuminators (48Ua..d; 48La..d) is employed in the image processor (8) to compensate for the distance dependent variations in illumination intensity of that single illuminator (48Ua) when energized.

13. The image-based inspection (2) device as claimed in Claim 1, wherein the image-based inspection device (2) further comprises:a feeder (16) adapted to transport grains received into the image-based inspection device (2) onto the upper surface (4L) anda vibrator (20) mechanically connected to the transparent portion (4) and operable to impart vibrations thereto and distribute received grains thereover.1614. The image-based inspection device (2) as claimed in Claim 1 whereinthe transparent portion (4) is a part of a removable plate insertable into and out of the image-based inspection device (2).

15. The image-based inspection device (2) as claimed in Claim 4 whereinthere is provided at least three, preferably four and more preferably five upper illuminators (48Ua..d) and a same number of lower illuminators (48La..d), with the upper illuminators (48Ua..d) being disposed to illuminate the received grains at the different illumination angles which are evenly spaced about a circle located in the plane parallel to the upper surface (4U) and with the lower illuminators (48La..d) being disposed to illuminate the received grains at the different illumination angles which are evenly spaced about a circle located in the plane parallel to the upper surface (4U).

16. A method for image-based grains inspection comprising the steps of:(a) feeding grains to be inspected into a transparent portion (4) of an image-based inspection device (2) as claimed in any one of the preceding claims;(b) obtaining by means of the image-based inspection device (2) a plurality of spatially co-registered images of the received grains, as captured images, each image of the captured images being an image of the received grains illuminated at a different illumination angle in a plane parallel to the transparent portion (4);(c) processing by means of the image-based inspection device (2) the captured images to form a composite image, in which composite image artifacts caused by the illumination at the different illumination angles are minimised; and(d) applying by means of the image-based inspection device (2) one of more image data, evaluation algorithms to the composite image to determine thereby visual characteristics of individual grains of the received grains.

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